IntroductionHigh tunnels are becoming increasingly popular for use by small farms who often market directly to consumers. Although they have proven to be economically advantageous to farmers who wish to capitalize on high prices obtained either early or late in the growing season, permanent high tunnel structures do represent a significant capital investment. The cost for a standard size tunnel, including plastic (two layers) and all the materials required for construction can range from $1.50-$2.50 per square foot without labor and freight charges. This represents an initial investment of several thousand dollars, which is simply too much for some small farms. Although most growers are able to pay for their tunnels within a few growing seasons, others cannot justify the investment. For this reason, extension and research personnel at the University of Kentucky have been working on developing a low cost high tunnel covered with a single layer of plastic that can be assembled or moved in an afternoon.

This low cost high tunnel only provides about 3 oF in frost protection, compared to 7 oF for a double poly tunnel. This tunnel design has proven to withstand 60 mph winds with little damage in central and western KY. This tunnel will not withstand much more than a very light snow event (<1 inch), however it is not meant to be used through the winter in parts of the country that receive significant snowfall. The best time to use this tunnel is for a few months in early spring and mid-fall that receive low daily temperatures and mild frosts. Demonstrations in Central and Eastern KY have shown that growers can reach the market up to three-four weeks earlier with tomatoes grown in this tunnel than in the field. The added income from these early tomatoes more than offsets the initial costs.

Additional benefits from this type of design include the ability to make the tunnel as long as is necessary. Because much of the labor is in constructing the endwalls, there is not as much difference in labor costs for constructing a 300 foot long tunnel compared to a 100 foot long tunnel. Obviously materials costs are more, but it allows flexibility for the grower depending on market conditions. Another positive for organic growers in particular is the ability to easily disassemble the tunnel and move it from one location to another. One of the central tenets of organic agriculture is the idea of crop rotation. Unfortunately with some of the more permanent high tunnel structures proper rotation is difficult. Often growers find themselves growing the same crop in the same location for many years. Failure to rotate annual crops does not comply with organic requirements, and in many cases results in high levels of soil-borne diseases. Organic growers in particular have had to adapt to find creative ways to deal with these diseases, including grafting of resistant rootstocks, biofumigants, and soil solarization. Being able to quickly move a tunnel allows growers to easily rotate and avoids many of these problems. The following are step-by-step instructions on how to assemble this type of tunnel. This design is constantly being modified to find the most economical use of money and labor while still providing a sturdy useful structure. Below is a detailed outline on how to construct this tunnel.

Constructing the high tunnel

In this tunnel we have already laid plastic in the field and transplanted. By assembling the tunnel over the already formed beds we can use traditional tractor mounted bedshapers and transplanters, saving the need for specialized equipment. Here anchors are made from one inch diameter pieces of steel pipe 18 inches in length with a single turn of auger flight welded to the end. Photo credit: Tim Coolong, University of Kentucky

These anchors are placed on eight foot centers the entire length of the tunnel. Generally they are spaced 12 feet apart, which is enough to easily cover two beds made on six foot centers. Photo credit: Tim Coolong, University of Kentucky

The anchors are then augured into the ground with a small hydraulic driven motor which can be hooked to a tractor. Anchors are driven into the ground so that the "hook" that is welded on the side is just at the soil level. Photo credit: Tim Coolong, University of Kentucky

Then 1.5 inch schedule 40 pvc pipe is placed over the anchors. Typically pipe can be purchased in 20 foot lengths. A 20 foot pipe will form a tunnel 12 feet wide at the based with a center height of just over six feet. Pipes should be painted with a latex paint. Experience has shown that non-painted pipe may cause plastic to degrade where it comes in contact with the pipe. Photo credit: Tim Coolong, University of Kentucky

Endwalls were constructed the previous season. These are made from 2x4 lumber and have a number of aluminum channels attached to them for fastening plastic. They are quickly put in place and attached to the end loops. In addition, ropes are run from either side of the door to

anchors that are sunk deep into the ground. Mobile home anchors are inexpensive and work well for this purpose. Photo credit: Tim Coolong, University of Kentucky

A lightweight metal pipe is then attached to each bow using aluminum cross connectors. A typical source of pipe would be the top rail for a chain link fence. This pipe is very important as it gives the entire tunnel rigidity. Demonstration plots showed that tunnels with the center pipe withstood very strong (60 mph) wind gusts while those without the pipe did not. The rigid pipe also helps shed water after rains. Photo credit: Tim Coolong, University of Kentucky

Ropes are then attached to anchors at each end and attached to the first three bows on either end in crisscross fashion. These ropes help tighten the tunnel and improve end-wall stability. Photo credit: Tim Coolong, University of Kentucky

Plastic is then unrolled and pulled over the house. Because the plastic is meant to be removed during the winter months, a lighter weight (4 millimeter) plastic can be used if desired. However, 6 millimeter plastic has shown to be able to withstand wind to a much greater extent than 4 millimeter in central KY. Once pulled over the hoops, the ends of the plastic are attached to the endwalls using "wiggle wire" put into the pre-fastened channels (shown in the far right photo). Photo credit: Tim Coolong, University of Kentucky

Then nylon rope is fed back and forth over the plastic attaching to the hooks that were welded on the side of the anchors. The rope is sent down the tunnel and attached to every other hook then it is brought back up the tunnel and attached to the remaining hooks. The rope is twisted at each hook so that the rope can be easily tightened as needed. By using the rope to hold the plastic cover down, one does not have to permanently affix the plastic to any base. Therefore when warm weather strikes the plastic can be pulled up on each side easily venting the crop inside. In fact, this type of structure was used to grow organic colored bell peppers during the summer in Lexington, KY. It served to keep rain off of the peppers, reducing fruit rot and the spread of bacterial spot of pepper. Photo credit: Tim Coolong, University of Kentucky

Total assembly time for a 160 foot long tunnel from start to finish can be done with 2-3 people in about 3-6 hours, depending on experience level. The end walls would take an individual about 2 hours each to build. While these tunnels only give about 2-3 oF of frost protection alone-more if an additional layer of plastic or remay is placed in the tunnel, they effectively increase the number of hours above 50 oF when used in spring. Thus they promote rapid growth and early fruit when used for tomatoes. Above is a picture taken on June 20, 2008, in the mountain region of East KY. The plastic had been removed, but one can easily see the difference in growth and fruit set on the tomatoes 'Mt. Crest' planted in the tunnel and those outside the tunnel. Both were planted on the same day in late April 2008. While not for everyone, these inexpensive tunnels can give growers a jump on the season without a large investment of capital. Photo credit: Tim Coolong, University of Kentucky

This is an eOrganic article and was reviewed for compliance with National Organic Program regulations by members of the eOrganic community. Always check with your organic certification agency before adopting new practices or using new materials. For more information, refer to eOrganic's articles on organic certification.

High Tunnels in W.Va.By Lewis W. Jett, Horticulture Specialist, 2010

Figure 1. High tunnels are passively vented, solar greenhouse structures covered with a single or double layer of polyethylene plastic

High tunnels are passively vented, solar greenhouses that are used to lengthen the production and marketing season of vegetable and fruit crops (Figure 1). No artificial heating/cooling or ventilation system is used within the high tunnel, and the only external connection is water for drip or micro-irrigation. Most high tunnels are covered with a single or double layer of polyethylene plastic (6-mil; greenhouse-grade) and have a useful life of 20 years if properly constructed and maintained. Crops within high tunnels are usually grown directly in the soil rather than artificial growing media, but soil-less substrates (perlite, compost, water) can be used for crop production within high tunnels.

High tunnels are very effective in collecting radiant energy from sunlight and using this energy to increase air and soil temperature to accelerate crop growth. Thus, in areas with abundant sunlight, high tunnels will be very effective for early-season harvest and lengthening the growing season.

High tunnels facilitate intensive crop production on a small land area and are conducive to sustainable farming practices such as intercropping, cover cropping, compost application and biological pest management. Crops within the high tunnels are protected from environmental stresses such as drought, wind, hail, rain and intense sunlight. Heavy rainfall prevents soil erosion within the high tunnel. The dry environment within the high tunnel keeps the plant canopy dry and reduces diseases and weed growth. High tunnels also physically exclude many pests from attacking the crop including insects and wildlife. As a result, many growers use high tunnels for organic production of fruits and vegetables. High tunnels have significantly lower investment costs and annual operating costs than standard greenhouses.

Figure 2. The site for construction of a high tunnel should be accessible, well-drained with abundant sunlight. (Photo Credit: E. Coleman)

The first step in high tunnel crop production is choosing a suitable site for the structure (Figure 2). Most high tunnels are permanent structures, so the site chosen will be the area for crop production for several seasons. Depending on location, building permits may be required. The site should have no history of perennial weeds or diseases and be well-drained and free of large stones. A soil test should be conducted in advance of choosing the site for the high tunnel. Since high tunnels are manually vented, they should be accessible. Water is an essential input for high tunnels, so access to water (surface or well) is necessary. While most high tunnels do not require electrical inputs, some growers choose to have electric fans which circulate air or inflate air between double layers of polyethylene.

High tunnels do not have to be constructed on perfectly level land, but a building pad or terrace can be made prior to constructing the high tunnel. Slope along the length of the high tunnel will facilitate water movement but should not be greater than 3%. Slope across the width of the high tunnel can be compensated by adjusting the height of the ground posts on either side. The construction pad can have sloping sides to channel water and snow runoff from the high tunnel structure.

The site should have full sun and good air flow since these are essential inputs to how well a high tunnel functions. Low areas that accumulate cold air (frost pockets) and water or sites close to a tree line or other structures which may cast a shadow on the high tunnel structure should be avoided. Also, areas with strong wind should have a wind break to prevent excessive wind stress or snow accumulation against the structure.

Orientation or positioning of the high tunnel is site dependent. The primary criterion should be maximizing passive ventilation. Therefore, for suitable ventilation, the high tunnel should be oriented so the length of the structure is perpendicular (i.e., at right angles) to prevailing winds at the site. In West Virginia, a north-south orientation is optimal for cross ventilation. Above the 40° latitude, most high tunnels are oriented in an east-west direction for maximum light interception particularly during low light months of winter. Most of West Virginia is below 40° latitude, so orientation is based on maximizing cross ventilation. Generally, the strongest winds which can damage the structure occur from the north-northwest in West Virginia, so a north-south orientation allows this potentially damaging wind to hit the smallest surface area of the structure (i.e., the end wall).

Figure 3. Quonset- (top) and Gothic- (bottom) shaped high tunnels.

High tunnels vary in length, width and shape. Ideally, the high tunnel should be at least tall enough to walk in with ease (> 7 ft.) or for equipment to be taken into the structure to till the soil, apply compost or create raised beds. Most high tunnels are 15-30 feet wide; 9-15 feet high and up to 200 feet in length (Figure 3). Optimal length for an individual structure with roll-up sides is approximately 100 feet. Many growers will start with a short, wide structure (e.g., 30 ft x 48 ft) and add on to the length in subsequent years. A shorter, wider structure is superior to a longer, narrower structure since the former will have less area exposed to the outside environment.

Larger high tunnel structures tend to store more heat during the day and are less likely to overheat. At night, when maintaining a stable temperature is crucial, larger high tunnels are less likely to cool down as rapidly. In addition, a taller high tunnel allows warm, buoyant air to rise in the structure facilitating ventilation.

There are two main structural designs for high tunnels: Quonset and Gothic. Quonset structures have a round roof with slightly shorter and curved sidewalls (Figure 3, top), while Gothic structures has a pointed peak (A-frame) with straight sidewalls (Figure 3, bottom). Gothic structures tend to shed snow and ice better than Quonset structures. Gothic structures also allow for a peak or gable vent to be added to the structure which facilitates air movement and ventilation.

Figure 4. (top) Sidewalls are rolled-up to facilitate cross-ventilation within the high tunnel. (bottom) PVC-framed high tunnels are functional high

tunnels.

Sidewalls on the high tunnel structure are usually rolled-up to facilitate cross ventilation (Figure 4, top). Therefore sidewalls should be at least 5 feet in height to maximize ventilation. During inclement weather, the sidewalls are closed.

If the site for high tunnel construction encounters significant snow or wind stress throughout the year, cross-braces (bracing of the bows) or other supplemental bracing of the frame may be necessary to strengthen the structure. Frames for high tunnels are usually galvanized steel but other materials can be used. Wood frames have been used as framing material for high tunnels. However, there is more blockage of sunlight from the wood frame than by other framing materials. Polyvinyl chloride (PVC) has also been used as a framing material for high tunnels (Figure 4, bottom). Most PVC-framed high tunnels are smaller in width than steel-framed structures. While PVC high tunnels can be lower in costs, they tend to be vulnerable to damage from wind, snow and ice unless they are properly braced.

After the site and general design of the high tunnel has been chosen, the structure can be constructed. Both spring and fall are excellent times of the year to build a high tunnel. The soil is amenable to construction, and the air temperature is suitable for pulling and stretching plastic over the structure. If building on a site which is presently in sod, the sod can be tilled after most of the high tunnel has been constructed.

Figure 6. The high tunnel structure must be square at each corner post.

The next step is to place the corner ground posts of the high tunnel so that the structure is ultimately square. The Pythagorean Theorem can be used to establish a 90° angle at each corner. The Pythagorean Theorem states the square of the hypotenuse of a 90° triangle is equal to the sum of the squares of the other two sides. Once one corner is square, the other three corner posts can be set so that the diagonals (length from one corner post

to the opposite end corner post) are equal (Figure 6). For example, a 30 ft x 96 ft high tunnel will have a 100.5 ft length diagonal (302 + 962) if the structure is square.

Figure 7. Corner posts can be set in cement to provide strength for the high tunnel structure. A leveling line is used to ensure each ground post is level. (Photo credit: A. Montri)

After the corner posts have been squared, they can be backfilled with cement to provide support for the structure (Figure 7). Obviously cement makes the structure permanent, so if there are plans to move the structure in the future, this step may be avoided. The remaining high tunnel ground posts are driven into the soil as straight as possible to various depths (usually no less than 18 inches) with a sledge hammer or post driver. A post level will be very useful in making sure each post is plumb. Also a leveling line (mason twine) connected to the bolt holes of each corner post can be used to drive each post to a depth which is level. A positioning or spacing jig can be used to evenly space the ground posts. Most ground posts are placed 4, 5 or 6 feet apart, with 4 feet the recommended spacing for high tunnels in West Virginia.

Figure 8. Purlins, cross braces, base boards and hip boards are attached to each bow to provide stability to the high tunnel frame.

The bows of the structure typically are 2-3 pieces and can be loosely assembled on the ground. Each bow is then inserted into the ground post and secured with 1-2 carriage bolts. Placing each bow in the ground post will require approximately 3 workers. After the bows are secured in place, the purlins should be attached to the bows. Purlins are smaller diameter pipes which are bolted (or clamped) to the bows to provide stability to the structure (Figure 8). Each high tunnel frame should have 1-3 purlins. Cross-braces can be attached to provide increased strength to the high tunnel frame.

After the purlins have been added to the structure, the baseboards and hipboards can be placed on the high tunnel. Baseboards and hip boards add strength to the base of the frame (Figure 8). For most high tunnel frames, 2 inches x 6 inches x 10 feet wood (or recycled plastic) boards are suitable. Pressure treated wood can be used for both hipboards and baseboards. Each section of baseboard is bolted onto the ground post or secured with a pipe strap (Figure 9). The baseboard and hipboard must be level across the length of the high tunnel. Each joint between sections can be spliced with a small segment of board.

Hipboards are attached 5-8 feet above the baseboards (Figure 8). Hipboards provide additional strength to the structure and are the boards in which the plastic covering the high tunnel structure is attached. Aluminum channel lock can be secured to the hipboard to provide a location for securing the plastic (Figure 9).

Figure 9. Pipe straps are used to secure the baseboards and hipboards to the high tunnel frame. Aluminum channel lock is used to secure the plastic

to the frame.

After the frame has been assembled, the end walls can be constructed. End walls vary in design from a simple fabric curtain to a wood-framed structure with doors (Figure 10). End walls provide strength to the high tunnel and should be built to provide easy access of people and machinery. End walls can be covered with polyethylene plastic, polycarbonate or plywood. The north-facing end wall can be covered with double layer of polyethylene plastic to provide greater protection from the north wind. Some growers will completely remove the end wall coverings during warm weather.

Figure 10. There is a diversity of end wall designs for high tunnel structures.

The plastic covering can be placed over the high tunnel structure after construction of the frame and end walls has been completed. There are many types of greenhouse plastics, but the plastic should be a UV- (ultraviolet light) treated plastic, 6 mil in thickness, with a useful life of approximately 4 years. IR (infrared) blocking plastic is also available and will provide better heat retention. A calm day with moderate temperatures will be optimal for covering the structure. Plastic should not be pulled over the structure if temperatures are lower than 60° F since it will be difficult to obtain a good stretch on the plastic. Ideally, the plastic should be taut and not flap against the bows.

Figure 11. Plastic (poly) is used to cover the high tunnel structure. The plastic is pulled over the frame after securing it with rope wrapped around

tennis balls.

At least 4-5 people will be needed to pull the plastic over the high tunnel. The plastic comes in a roll which is unrolled along the length of the house (Figure 11). After unrolling the plastic, a handful of the plastic can be folded around a tennis ball at various distances. Rope is then tied to this ball and thrown over the frame (Figure 11). Carefully, the plastic is pulled over the structure, making sure it is square with the frame.

The plastic is attached to the frame with wiggle wire or polylock placed in each aluminum channel lock on the hip board (Figure 12, left). One side should be completely secured first then any slack in the plastic can be pulled and the other side wired. The plastic should be as taut as possible. The channel lock on the end bows are used to hold the plastic to the end walls of the high tunnel. The plastic is clamped on to a metal roll bar (purlin pipe) which serves as the bar for rolling the plastic up or down on each side wall. A “T- or L”- shaped handle can be made to serve as a hand crank which makes rolling the pipe up easier. Rope can be laced on the sidewalls to hold the plastic sidewall closer to the frame and prevent flapping in wind (Figure 12, center).

Figure 12. (left) Plastic is secured to the frame with wiggle wire within each channel lock. (center) Rope can be laced along the sidewall for tightening

the roll-up sides. (right) Water runoff from the high tunnel can be collected and used for irrigation.

To prevent excessive water movement into the high tunnel, a drainage ditch should be dug to channel water away from the high tunnel. A woven landscape fabric can also be used to divert excess runoff water and prevent weeds from growing close to the high tunnel. Rain gutters can also be secured to the hipboard and used to channel water into a storage tank that can be used to irrigate crops within the high tunnel (Figure 12, right). Batten tape can be used to secure the plastic to the end wall frame. Batten tape is applied over the plastic and stapled into place.

Additional High Tunnel Construction Resource Material:

The Hoophouse Handbook. 2003. Growing for Market. L. Byczynski (ed.).

The Winter Harvest Handbook. 2009. E. Coleman. Chelsea Green Publishing Co., White River Junction, VT

High Tunnel Production Manual. 2008. Penn State Center for Plasticulture.

Yard & Garden Line NewsVolume 6 Number 15 September 15, 2004

Features this issue:

High Hopes for High HoopsGolden Rust on GoldenrodsWest Nile Virus Cases Down Incorporate All-America Selections into Next Year's Garden Late September Garden TipsEditorial Notes

High Hopes for High HoopsRobert Olson, Regional Extension Educator, Horticulture

This summer's dismal weather has prompted a lot of interest in garden structures that extend the growing season. Tops on this list are "high hoops" - also called "high tunnels" or "hoop houses". There names are interchangeable, and they've become the most popular form of greenhouse structure for many reasons.

High hoops were originally designed for commercial growers, but their popularity has lead to the development of smaller structures that are being utilized by backyard gardeners. Regardless of size, the working principles are the same.

What are they?High tunnels are unheated, plastic-covered structures that provide an intermediate level of environmental protection and control as compared to open field conditions and heated greenhouses. Plantings in high tunnels are placed directly into the existing soil of your farm field or garden, as opposed to production on benches or raised platforms like in greenhouses.

High tunnels are tall enough to walk in comfortably and to grow tall, trellised crops. Homeowner models that are 14 feet wide reach an interior height of about 8 feet; commercial models that are typically 30 feet wide reach a height of about 15 feet. The commercial models also have end panels that allow small tractors to drive through.

Greenhouses are permanent structures that are taxed as real property, whereas high tunnels (being temporary, moveable structures) are not. Greenhouses are covered by glass, rigid panels or double-layer plastic, but high tunnels are covered with a single layer of plastic.

A critical component of high tunnels is their ventilation system which generally

Major components

Illus: Penn State

Basic s

consists of roll-up sidewalls that can be opened in the morning and rolled down at night or in cold weather.

Because the entire system is enclosed, no rainfall enters the tunnel. All water is supplied by the grower, generally via trickle tubes that are placed under plastic. The interior of the tunnel is completely dry and relatively clean. Harvested produce is very clean, greatly reducing the washing of produce. Research validates that fresh produce from tunnels also has enhanced shelf life as compared to field-grown produce.

Unlike commercial greenhouses that can cost up to $20 per square foot to construct, high tunnels can cost as little as $0.50 per square foot. This modest cost can result in a high return on investment, and in a season like this year growers with high tunnels reported that they paid for themselves the first season. Proponents of the tunnels see them as great income-generating technologies that college students and enterprising high-schoolers could manage as a summer job. One commercial-scale tunnel (30 feet X 90 feet), costing under $2000 to construct, could gross over $6000 if planted to tomatoes that are sold at farmer markets or roadside stands.

Unexpected BenefitsEveryone expected tunnels to provide a heat advantage compared to field-grown production. Few people, however, expected the dramatically reduced pest levels that are being realized. Growers and researchers alike are impressed with the excellent weed, insect, and disease control within the tunnels. Growers that have been cautious about organic production are now giving organics another look.

Reduced disease One of the most impressive features of these systems to date is the diminished disease pressure. The tunnel systems, by keeping the interior completely dry, result in an environment less conducive to several of the problematic disease organisms. Think about it, the foliage is always dry and there is no soil splashing compared to field grown systems. Add to this the wind protection factor from blowing soil and the enhanced vigor of plants, and you have an environment that allows crops to out-compete pests.

A critical component to managing diseases is the sidewall ventilation system. Without the open sides, the humidity levels would lead to a rainforest environment and subsequent disease haven. So during most days, the sidewalls are rolled open. When nighttime comes, the grower closes the tunnel to keep the cooler evening air from condensing on the leaf surfaces, thereby keeping the foliage completely dry. Just walk your lawn in bare feet after sundown and you'll know just how wet foliage can become. I'm reminded about condensation every winter morning when I scrape the ice from my car's windshield, whereas the cars parked in the garage are nice and dry. It makes me wonder, why is it that I am the one who pays for the cars, the insurance, the mortgage, and puts gas in the cars, yet I'm the one who has to park outside in the cold? I digress.

More InformationIf your interest is piqued, you'll probably want to do a little research on the subject. My colleague, Terry Nennich, is developing a written manual on high tunnel management based on Minnesota research which will be designed for commercial growers. The principles will be applicable to the backyard gardener as well. Another great source for information is Penn State, which has a large research effort devoted to plasticulture, including high tunnels. They can be accessed at: http://plasticulture.cas.psu.edu/.

Golden Rust on Goldenrods Janna Beckerman, Extension Plant Pathologist

This year has been an interesting one for plant pathologists. As our long, cool wet spring, became a cool, dry summer, a variety of diseases that are commonly overlooked became unusually severe. One such disease is pine needle rust. However, the severity of this disease manifested itself most severely on the alternate hosts: Goldenrod (Solidago spp.) and Aster (Aster spp.)

When forest pathologists discuss pine needle rust, they refer to the economically important timber hosts of jack (P. banksiana), Austrian (Pinus nigra), red (P. resinosa), ponderosa (P. ponderosa), mugo (P. mugo), and Scots (P. sylvestris) pine. Economically speaking, the alternate hosts are of little value-except to the homeowner whose plant is suddenly orange. This disease is caused by the fungus Coleosporium asterum. Although it doesn't look that way, this rust causes little damage on either host. In pines, browning and needle death on lower branches is unattractive, and may slow the growth of young pines. On goldenrod and aster, severe infection may result in a reduction or loss of flowering.

The life cycle of pine needle rust takes an entire year to complete. Currently, on the aster and golden rod, we are seeing the uredinia developing on the leaves and stems. This stage can repeat itself under conducive weather conditions, and render the entire plant orange, as we've seen! Eventually, urediniaspores produce a new spore shape, the teliospore. The teliospores germinates to produce basidiospores that are windblown to pine needles, where new infections begin. These infections will not be seen until next spring.

In the meantime, the fungus survives winter in the infected pine needles. The

Severe infection on goldenrod.

Individu

To make sure the disease is rust, check your hand

following spring, small yellow spots appear on infected needles that develop into columns that split releasing orange spores. These spores are wind- dispersed and infect the underside of leaves of the goldenrod and aster. Orange structures called uredinia develop on the leaves and produce the characteristic orange spores that we are seeing now.

When diagnosing rust diseases, it is important to actually see spores! Plants turn orange for many other physiological reasons (nutrient deficiency, insect feeding, herbicide damage, etc.). Finding spores on your hands is a tell-tale sign to diagnose this disease!

Although pine needle rust rarely causes damage to mature trees, it can render plantings of asters and goldenrod unbelievably orange. Fungicides labeled for the control of rust on perennials contain active ingredients like sulfur, chlorothalonil, myclobutanil, and mancozeb. Replacing plants with rust resistant asters Removal of alternative hosts from the immediate vicinity of the trees will reduce infections of pines. Cultural practices such as thinning foliage, watering during dry periods, mulching, and fertilizing may reduce infections. Reportedly resistant goldenrod cultivars include: 'Baby Sun,' 'Baby Gold' and 'Goldkind.' The PREP trial in Rosemount has found that Aster 'Alma Potshke' was very resistant to rust, but that the A. dumosas series 'Wood's Pink' and 'Wood's Purple' were very susceptible and susceptible, respectively.

Please check out the new diagnostics web pages athttp://www.extension.umn.edu/projects/yardandgarden/diagnostics/

West Nile Virus Cases Down Jeffrey Hahn, Assist. Extension Entomologist

Although many Minnesotans will think of 2004 as the summer that never was, we may also remember it for the low incidence of West Nile virus (WNV) that we experienced. Our first detected activity of WNV in Minnesota occurred in 2002 when we recorded 48 human cases and zero deaths. In 2003, the number of human cases tripled to 148 along with four deaths

The big question was what would happen in 2004. Would the number of cases continue to increase? Unfortunately, entomologists and vector ecologists don't know enough about this disease to accurately predict how the disease will cycle. But fortunately instead of continuing to go up, the number of WNV cases have fallen. So far this year, there have been only 19 cases and one death recorded in Minnesota (as of September 14, 2004). Although more cases are likely to be reported before the end of the year, (most cases in Minnesota are reported during August and September) the majority have undoubtedly occurred.

Interestingly, the number of horse cases this year are also considerably down. To date, there have only been 6 instances of horses infected with WNV. This is after 992 cases in 2002 and 74 cases last year. Although there may be several factors that help explain this, much of this decrease is probably attributable to the increased protection of horses that owners have given them, especially by vaccinating them.

However, there is not such an easy answer for humans to explain why the incidence of WNV has gone down. It is natural to assume that the cooler weather had a significant effect on WNV cases. While it is true the weather probably did slow down mosquito activity, it is unlikely the only reason. There does seem to be a consistent trend in other states for the rates of WNV to cycle down after a large increase of WNV has been first detected, although the exact reasons are not clear.

It is interesting to look at New York, the first state to record WNV. In 1999 they detected 62 human cases of WNV with seven deaths. Those numbers went down in 2000 to 14 cases, zero deaths and to 15 cases and two deaths in 2001. The number of human cases rose in 2002 to 83 (five deaths). In 2003, activity was down to 71 cases but with 10 deaths. So far in 2004 there have been only 5 cases with no deaths. Although the incidence of WNV may go up, it always seems to come back down to very small numbers. (Keep in mind that for a state with such a large

Disease outbreaks Image: CDC

population as New York, 100 or fewer cases is just a small percentage of the overall population).

There isn't an easy explanation for this pattern in New York or similar cycles in other states, including Minnesota. That makes it difficult to predict whether the current trend in Minnesota will remain in a downward cycle or fluctuate. The disease is too new here to understand it completely. We need to continue to learn about WNV to better understand what our potential risk may be.

For more information, see also the Minnesota Department of Health West Nile virus web site, http://www.health.state.mn.us/divs/idepc/diseases/westnile/index.html

Get the low down on this month's insect pests at Insects http://www.extension.umn.edu/projects/yardandgarden/EntWeb/Ent.htm

Incorporate All-America Selections into Next Year's GardenDeborah Brown, Extension Horticulturist

It's always fun to try new seeds, and when the flower or vegetable is an All America Selection winner, it's a pretty good bet that it will perform well in your garden. Here's a sneak preview of the All America Selections chosen for 2005. You should be able to order seeds from a number of mailorder or Internet catalogs. Some winners will also be available as young transplants in packs at local nurseries and garden centers.

Flowers: Gaillardia ‘Arizona Sun,' also known as "blanket flower," is a neat, compact cultivar suitable for container growing. Blanket flowers are usually short-lived perennials in our climate. Should you hope to over-winter it, plant it in the ground rather than in a container.

Catharanthus ‘First Kiss Blueberry,' usually called "vinca," is the bluest yet produced, but it's still a violet-blue rather than sky blue. Vincas have glossy, leathery leaves and can take sunny, hot, dry conditions. They also bloom in light shade, though not as well as in a sunny site.

Zinnia ‘Magellan Coral' produces double flowers, five to six inches across! It blooms early – only six to nine weeks from seed – and, like other zinnias, grows best when seeded directly into the garden.

Vegetables: ‘Fairy Tale' eggplant is pretty enough to categorize with the flowers instead of the vegetable winners. The petite plants produce small purple and white striped fruit that are tender and tasty when anywhere from one to four ounces in size.

‘Sugary' tomato produces grape-like clusters of ultra sweet "cherry" tomatoes that are oval, with a little point on the end. They can be harvested about sixty days

Gallardia 'Arizona Sun'

Vinca 'First Ki

Tomato 'Sugary' All Photos: AAS

after transplanting, and may be grown in large containers or supported, directly in the ground.

‘Bonbon' is a winter squash with an upright, semi-bush habit, requiring less garden space than most winter squash. The boxy, four pound fruits are said to have superior eating quality – sweet, with a creamy texture. They ripen roughly eighty-one days from planting, sometime the latter part of August in southern Minnesota.

Late September Garden TipsBeth Jarvis, Yard & Garden Line

Compiled from conversations with Patrick Weicherding and Bob Mugaas, Regional Extension Educators.

These recommendation are based on Twin Cities temperatures. Adjust for northern Minnesota.

Trees and Shrubs:Water trees, especially those 5 years old or less. Older trees, theoretically, could be damaged by heavy watering because it could prompt new growth that can't be supported by drought-damaged roots. However, recent substantial rains will lighten the drought stress on established trees, especially since they're shutting down in preparation for winter. Soil moisture is an important aid in the development of the abscission layer, so the rain will help the leaves fall. Drought stressed trees will hold leaves well into the winter.

Water all evergreens and young trees until the ground freezes. Water deciduous trees and shrubs as best you can until the leaves fall. Remember that lawn grass captures the vast majority of applied moisture, so water more than an inch within the dripline of trees. The soil should be damp at least 6-8". Plase see: http://www.extension.umn.edu/yardandgarden/YGLNews/YGLN-Sept0103.html#water"

Early fall color is a drought response indicating that the trees can't support the leave they still have. Poplars/cottonwood and ash are typical leaf "shedders" when stressed. Maples are another issue--that's maple decline--when trees are so stressed they can't recover.

Pruning for cosmetic or structural purposes should wait until the dormant season. Remove diseased trees now. Be sure all elm firewood has been de-barked before storage.

Hold off on pruning trees susceptible to fire blight right now. Wait until late winter. The most commonly affected are: pear, apple, crabapple, mountain ash and cotoneaster. Read about it at: http://www.extension.umn.edu/projects/yardandgarden/ygbriefs/p223fireblight.html

Shop fall tree sales. Pick well shaped trees with wide branch angles where applicable, and desired fall color. Plant in the ground by the middle of October.

Start thinking about rodent protection of new trees--it should go on before November 1, so shop around for 1/4" hardware cloth to surround tender-barked young trees.

Lawns:

It's a great time for perennial broadleaf weed control.

We're coming up to the tail end of seeding, though if it stays warm and rains, the rest of September could be suitable. Sooner rather than later is the key as grass needs to be established before winter's cold arrives.

Sodding can be done for another month or so.

If you overseed, work up the soil so you get good soil to seed contact. Tossing seed on a thatch-covered lawn will accomplish nothing.

You can start reducing mowing height. A 3" cut can be reduced to 2.5". This will reduce floppiness that can help reduce future snow mold problems and increase growing points/density of plants.

Be sure to water if we get into a dry spell, even though temperatures may be cooler.

Wait until closer to the end of October for the late season fall fertilizer application. If your grass is a bit anemic now, a half pound of nitrogen per thousand square feet of lawn could be applied now followed by the late fall fertilizer application of a full pound of nitrogen.

Core aerating is still possible. Dethatching should wait until spring. If you have heavy thatch, do a a real thorough core aerating job now. Grass needs 6-8 week of recovery time.

Everything you ever wanted to know about lawn care and repair can be found at the Sustainable Urban Landscape Information Series website at: http://www.sustland.umn.edu/maint/index.html. Click on lawn maintenance and scroll down to the lawn care calendar for timing.

Flowers:Plant spring flowering bulbs soon. All but tulips need to be planted early. Tulips can be planted as late as you can dig in the ground. For more info, see Spring Flowering Bulbs http://www.extension.umn.edu/projects/yardandgarden/ygbriefs/h120bulbs-spring.html

As plants yellow and die back, it's ok to cut them back and compost any healthy plant tissue.

Editorial Notes

Joe Pye weed is noted for growing taller in the wild and staying shorter in cultivation. It could be a light issue, as wild plants may be trying to grow into more light. This photo, taken at Eloise Butler Wildflower Park many years ago, was in an opening in the woods and quite tall.

In the next issue, Bob Mugaas, Regional Extension Educator, Horticulture, will be writing about why lawns flower and set seed in the spring. The process starts in the fall. That will be published Oct. 1. I've asked a couple of grad students to write a piece on the physiological changes plants, other than turf grass, undergo in order to flower. In the future, Patrick Weicherding, Regional Extension Educator, Forestry, will be writing about new research findings on the timing of pruning trees for disease prevention and to prevent pruning damage.

Please feel free to cut and paste any of the articles for use in your own newsletters. All we ask is that you give our authors credit.

Back issues Yard & Garden Line News are on the Yard & Garden Line home page at www.extension.umn.edu/yardandgarden/.

Deb Brown answers gardening questions on Minnesota Public Radio's (MPR) "Midmorning" program on the first Thursday of every month at 10 a.m. The program is broadcast on KNOW 91.1 FM, and available state-wide on the MPR news radio stations.

For plant and insect questions, visit http://www.extension.umn.edu/askmg. Thousands of questions have been answered, so try the search option in the black bar at the top left of the board for the fastest answer.

Joe Pye weed in wild Photo credit:Beth Jarvis

If you would like to receive an e-mail reminder when the next issue of the Yard & Garden Line News is posted to the web, just send an e-mail to: listserv@lists.umn.edu (note: the second E in listserve is omitted), leave the subject line blank, then in the body of the message, type: sub yglnewslist or to unsubscribe, enter: unsub yglnewslist

Happy gardening!

Beth JarvisYard & Garden Line Project Coordinator

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Building a High Tunnel Hoop House / Green House : Part 1

BY ANDY, ON MARCH 21ST, 2011

Quite a while back we asked for input on Facebook from everyone to see what YOU would do if you were out here on the farm… the question was – would you buy a JD Gator or would you buy a greenhouse? The results were split 50/50 so we knew we needed to make both happen. As you know – the Gator transaction was completed a while back… As for the green house / hoop house… well, construction started this weekend. The process is actually very straightforward and we are moving through the steps at a pretty rapid pace. Basically we bend all the tubing we need for the hoops, we pound some slightly larger diameter tubes about 4 feet into the ground, screw the arches together and slip the arches into the tubes. We start with standard line posts for a chain link fence and cut them into 4′ lengths with a metal cutting blade on the 12″ chop saw.

The tools for pounding the tubes into the ground are pretty simple and with the ground being so wet right now the process is actually pretty easy. First we marked off the house with string in a 12′ x 28′ rectangle. Then using a mallet the post gets pounded about 6″ into the ground. The level and the big post driver help get it father down and straight too. The

last 6″ takes a sledge hammer… that tends to round over the top of the pipe in the ground but as long as the 1 3/8″ pipes for the hoops fit we are OK. If the opening gets too small, we use a bar to pry open the rolled metal. Very simple process

actually.

To bend the tubes we mounted a 3/4″ sheet of plywood on the back of our Gator and then mounted the tubing bender to that. Then it’s a little elbow grease and a lot of back pulling to make the straight tubes that were bought at Home Depot for chin link fencing into the curved halves of the hoop structure. Once we got the mechanics worked out I can feed and bend and Kelli can pull and keep the tube flat. It takes about 30 seconds to bend half a hoop.

After bending the tubes Kelli removes them from the opposite end of the device and then stacks them in the barn. The ends are painted to match the corresponding other half of the arch so when they go out to the field we know which ones go together. To build this particular structure we need 28′ of support which is one arch every 4′… so that’s 7 arches, plus one for the end… and 2 bars per arch… calculator says… 16 total tubes bent.

The last step is the most rewarding… inserting the ends of the arches into the tube in the ground. The arch (or hoop – that’s why they call these a hoophouse) measures about 14′ wide when it’s not flexed so we “squeeze it” down to 12′ to

make the hoop house structure. The insertion of these hoops under tension adds a great deal of strength to the finished structure.

As it sits now you can see we installed a single hoop mainly to feel good about our efforts… but to the left of the picture you see a whole bunch of pipes laying in the weeds waiting to be driven into the ground so we can attach more hoops. We still need to build the base around the hoops out of some pressure treated 2×8 lumber, install a support along the spine of

the structure, build some ends and then finally install the plastic… that’s ALL.

If you liked this post, check out these:

• Building a High Tunnel Hoop House / Green House : Part 2 - (Really Similar)

• Building a High Tunnel Hoop House / Green House : Part 3 - (Really Similar)

• Dampening Off! - (Interesting)

• Gators and Greenhouses and Greenbacks, ohh my! - (Interesting)

Building a High Tunnel Hoop House / Green House : Part 2

BY ANDY, ON APRIL 10TH, 2011

Just to set the record straight before we get into this… The last post on Pigs Milk Cheese was an April Fools post (nice job to those who caught the date). Also – if you haven’t ordered your pastured chicken yet – you should.

With the posts in the ground (from the first post) there’s still a fair amount of work to be done, we needed to get a wooden base around to frame up an attachment point for the double layer of plastic. We also need to get the hoops installed, the spine installed and then some nifty wind bracing installed so we have a prayer of sustaining those 60 MPH+ winds we get on the hill here without watching our hard work blow into the next county. So we started

with the base boards. normally people install larger treated 2x something boards – but looking at the price of lumber we decided to go with a much less expensive treated 5/4×6 non-premium decking board. In reality, these base boards don’t offer much more that a place to attach the plastic so there’s no need to them to be super heavy duty. They are attached

by drilling a hole through the board and the post and then attaching with a 1/4″ stainless bolt and nut.

The challenge of installing the the base boards is really all about level ground. The posts were driven in to an approximation of “level” – but adding the base boards required a fair amount of finagling. All said and done, the lower end of the structure has the baseboard about 4″ above the soil and te high end has the boards about 3″ into the soil. And

we picked one of the more level areas to site the greenhouse!

With 3 sides of the base completed (we left the end with the door open as it cuts through the existing low tunnel AND we are still debating about making the end door tractor friendly as well) it was time to start to assemble the superstructure,

and all that starts with an end. So, we used the backhoe to dig a couple of 3′ deep holes and dropped some old treated 2×4′s in. Those were then lined up with the end hoop, cut to length, notched and bolted to the hoop itself.

The spacing for the end posts we determined by the 2 tripple track storm windows that came off the barn when we resided it. They are big and will provide LOTS of ventilation on the west end of the green house.

Once that “wall” was built, the process really takes off. It becomes an exercise in joining the 2 halves of the hoops we bent with stainless self tapping metal screws, then inserting them into the posts that are attached to the base boards. After all the hoops are up, the next step was to use some special (and expensive) clamps designed to attach the spine

down the top ridge line. This addition locks all the hoops into a single structure and really provides a massive amount of rigidity to the structure. Up until this point we kinda felt like we were kids making a sandcastle at low tide… just waiting for the wind to pick up and blow out wiggly metal structure into 100 little pieces. But with each rib being attached to the

spine (yes, I loved Moby Dick), the whale of a structure became more and more solid.

After the last section of the spine was installed and cut to length all we had left todo was install a set of diagonal wind braces and the windows. All in all, the steps in this part of the installation only took about 5 hours over 2 days and were the most rewarding steps. We can now stand back and look at something that resembles a green house. And the most

rewarding part has been the discovery of how strong this structure really is. The spine and the wind bracing has made the and wall solid and we really think this structure is going to be able to take the winds. As a matter of fact we are already thinking of LOTS of ways we can expand this design for something like a roaming pasture warmer for the chickens in the

middle of winter… At any rate, tonight we place the order for the plastic, inflator fan and various other parts. Time marches on and our seedlings in the basement are getting ready for a nice warm “real sunlight” house!

For a few more pictures of the process – visit our Flickr Photostream to check things out.

If you liked this post, check out these:

• Building a High Tunnel Hoop House / Green House : Part 1 - (Really Similar)

• Building a High Tunnel Hoop House / Green House : Part 3 - (Really Similar)

• Dampening Off! - (Interesting)

• Gators and Greenhouses and Greenbacks, ohh my! - (Interesting)

Building a High Tunnel Hoop House / Green House : Part 3

BY ANDY, ON MAY 3RD, 2011

Plastic cover ready!

We finally had enough of a break in the wind and weather around here to do the last of the work on the hoop house / high tunnel. That “last of the work” would be to install the plastic. A quick search of the web on how to install greenhouse

plastic didn’t really offer a lot of suggestions or help. Further more we knew we were going to be inflating the two layers of plastic with a greenhouse inflation blower… and that too isn’t well documented out there. So – here’s the tools,

techniques and lessons we learned in the last phase of constructing this greenhouse.

Wiggle wire

First, we decided that the easiest way to attach the plastic was using a wiggle wire system like most commercial greenhouses. The wiggle wire is a bent piece of stainless steel wire that fits inside a specially

designed aluminum channel – the wire presses and pulls on the plastic and the channel follows the contour of the greenhouse. The idea is to basically close the plastic over the structure on 4 sides kinda like a big 4 sided Ziplock bag then pump air into the space between the plastic to create a layer of insulation and keep the plastic taunt so the wind can’t grab

a hold of it and rip it off. Pretty simple system that goes together pretty fast. time will tell how it handles the winds we get up here!

How do you get plastic on a greenhouse?

The long side

That question was one we couldn’t get a really good answer on. We waited for a calm day (no wind) and then pulled the plastic layers over the hoops. The inner layer is a infrared reflective layer to keep the heat in at night and the outer layer is typical greenhouse plastic. Once it’s draped over the structure we picked a corner and started working from there. The

general approach is to close things up like a plastic bag… starting at one side and working our way around. By doing things like that the plastic can shift and slide as we pull on it and we can minimize wrinkles in the final layout. So, we

started on one of the longest sides by installing the wiggle wire the entire length.

From there we then went up along the end hoop. The only place s the plastic is attached is on the long bottoms and then along the contour of the end hoop (again – so the entire greenhouse can be inflated). The process works best with at least

2 people, we could have easily used a third. One person pulls on the plastic to ensure it’s tight and the other person installs the wiggle wire. (Kelli will tell you the worst job is the hand cramps you get for pulling so hard on something as slippery as plastic – I might tell you the worst job is mashing your fingertips over and over with the wiggle wire in the

channels… honestly, neither job is horrible - but also not something you look forward to repeating!)

Inflator - go!

With the plastic secured along almost the entire greenhouse, we left the corner where the inflator gets installed un attached just enough so I could worm my way in-between the 2 layers of plastic and cut a hole through the inner layer. In

this picture you can see the white dot looking thing – that’s the diffuser that the inflator motor blows through. It sites between the 2 layers of plastic and keeps the space pressurized. One thing I decided to do as an added precaution was to

place a piece of 4″ wide greenhouse tape over the spot where I cut the hole. That should help keep this area for developing any stress tears over time as the wind punishes the structure.

Yup - it's inflated.

After the inflator fan was installed we finished installing the last of the wiggle wire in that corner and trimmed off the excess plastic. We then fired up the fan and let the greenhouse puff up. It was an impressive site to see as the wrinkles

all disappeared and the plastic shell became a component of the structural support for the building. Very impressive design. We have noticed that our blower seems to be a little “over active” and we have ordered a control switch to dial in

the perfect amount of “inflation”.

All in all without a final tally of the receipts the project came in a little more than we thought it would (don’t they all) BUT the structure is a LOT more substantial than we expected and are pretty optimistic that it will sustain the big winds we get. Total price tag including all the mistakes and the bender we will have for years : around $1500. So given it’s size, that’s like $4.46 a square foot of protected, sun warmed space (not to bad) We also learned a TON in doing this, knowledge that would have been REALLY expensive to acquire on a full fledged kit. Actually – after we finished it we both looked at the space next to it where the bales of hay sit and discussed how long the next one will be. :) The last thing we have left to

do is attach the last little rolled up plastic that is along the hooped ends to the faces. It’s a small job (just not done).

We also learned several things we would differently next time. Big doors on both ends. Translucent panels on the ends. Grade the area where it will be constructed first (building this OVER the low tunnel was stupid and caused things to be

much more difficult than they needed to be). Install water hydrant inside the house for easy water access. I’m sure there will be other lessons learned too – but in the end – we are REALLY, REALLY happy with our homemade greenhouse! (for a

few more pictures visit our Flickr Photostream)

The plants that have been moved inside the new greenhouse seem to like it – but they are not very vocal anyhow… Stay tuned for a tour of the inside…

Our first homemade greenhouse

If you liked this post, check out these:

• Building a High Tunnel Hoop House / Green House : Part 1 - (Really Similar)

• Building a High Tunnel Hoop House / Green House : Part 2 - (Really Similar)

• Dampening Off! - (Interesting)

• Gators and Greenhouses and Greenbacks, ohh my! - (Interesting)

Part I Site Planning and Construction

Article

Constructing a Simple PVC High Tunnelby Jim Hail, Robbins Hail, Katherine Kelly, and Ted Carey

Introduction This low-cost, 30’ long by 18’ wide high tunnel is constructed using PVC pipe for hoops. The materials cost roughly $500 (including shade cloth for summer production) and we didn't shop for the best buy on materials and lumber. A slight disadvantage of the design is that curvature of the hoops may allow rain to run inside the edge of the house when the sides are raised for ventilation. One person can complete most of the construction, but inserting the hoops and putting on the plastic requires at least two people. Also, it is nice to have someone to share the heavy work of driving in the ground posts. A crew of four can easily construct a high tunnel of this design in a single day.

LINK:

How to Build a High Tunnel

by Amanda Ferguson,

University of Kentucky

The dimensions of this high tunnel design may be scaled-down if you have limited space available for your high tunnel. At a lesser diameter, or in well-protected locations, it may be possible to use 1” PVC for the hoops, with 1½” PVC for the posts. The length of pipe to use for hoops may be calculated using the formula for the circumference of a circle, (3.14)r, where r is half the width of your tunnel. Add 3’ to insert into the ground posts.

LINK:Hoop House Construction

for New Mexico: 12ft X 40ft Hoop

House PVC will react with the polyethylene greenhouse covering, so in order to attain the expected 4-year life span of the plastic, measures should be taken to prevent contact between the PVC and the polyethylene covering. This may be done by painting or taping the side of the PVC hoops that will be in contact with the plastic. Having said that, the oldest high tunnel at Bear Creek Farm in Osceola, Missouri, is eight years old and is still covered by its original plastic, which is in contact with the PVC hoops.

Note: Our procedure calls for driving 3’-long PVC posts into the ground after laying out the baseboards. We have found this to be a convenient way to proceed. However, in shallow, tight or stony soils, it may be necessary to dig holes using an augur, and then set the posts in concrete. If it is likely that you will need to do this, then posts should be set before laying out the baseboards.

Materials

Material Dimension Quantity NotesTwine & Pegs For corner and baseboard layout.

Lumber 2" x 6" x 10’ 6

For baseboards. The boards will be in contact with the soil, so you might consider a rot resistant wood, such as cedar or redwood. If you will be growing food crops in the tunnel, it’s probably best not to use treated lumber because of possible health concerns.

1" x 4" x 10’ 6 For hip boards.

2” x 4” x 8' 18 Lumber for attaching baseboards, bracing end hoop, and framing end-walls.

2” x 4” x 10' 4Lumber for framing doors. Depending on door size, amount of bracing desired amount may vary. We put a 32”-wide door on each end.

Furring strips 1" x 2" x 10’ 12

For attaching plastic to hip boards and end-walls. Poly tape may also be used for attaching plastic to end walls. Wiggle wire is a more costly but convenient method for attaching plastic to hip boards.

Schedule 40 PVC pipe

1½” x 20’ bell-end

12 For 11 hoops + purlin.

10’ x 1½”straight-end

12 For 11 hoops + purlin.

3’ pieces of 2”

22 For ground posts. Requires 8 10' pieces

Primer & Glue . . For connecting PVC pipe

Carriage bolts 4½” x ¼” 33 For attaching hoops and posts to baseboards, and hoops to purlin – purchase bolts, washers and nuts.

Deck screws 1½” 1 lb 2½” 2 lb 3½” 2 lb Chain link fence top rail

31' 2 For roll up sides.

PVC fittings 1” . To make handles for roll up sides.

Self-tapping screws

. . For connecting top rail pieces, and for attaching PVC handle to roll-up side.

Greenhouse polyethylene

30’ x 34’ 1

For covering the house use 6 mil UV stabilized. For the end walls, you may use a lighter gauge material, since it may be taken off each summer to enhance ventilation.

Shade cloth 30’ x 25’ 1 White 38% shade cloth with grommets sewn every 3’.

Tools

Step ladder Level and plumb line Stapler and staples Sledge hammer for driving baseboard stakes and PVC ground posts Saw for cutting lumber and PVC Drill with screwdriver bit, and with extended ¼” wooden drill bit for drilling holes for

carriage bolts

Site Preparation and Construction 1. Site Preparation. Choose a good site for locating the tunnel with respect to light,

drainage, access, irrigation, etc. Prior to beginning construction you may wish to build a slightly elevated, level pad, or take other measures to ensure that run-off water will not flood the high tunnel, particularly in the winter. Orientation with respect to wind is not critical, but we have oriented ours east west, meaning that prevailing winds are usually from the sides.

2. High Tunnel Layout. Mark the corners of a rectangular area 18’ wide by 30’ long.

Make corners square by ensuring an equal distance between perpendicular corners (should be 35’ between outer corners of pegs). Drive 2”x2” peg into the ground at the corners and stretch twine around the outsides of the corner posts where baseboards will run. It is not essential for the tunnel to be level, but this certainly helps to make doors square. To layout a level tunnel, use a level to adjust the height of the string to be used as a guide for baseboard placement. We have built ours on slight slopes, with the baseboards following the slope, and hip boards parallel to the baseboards.

3. Set Baseboards. Cut 14 2’ pieces of 2”x4”, and cut points on ends for driving into the ground. Drive in these stakes for baseboard attachment on the inside of the guide string, orienting the broad side of the 2”x4” parallel to the string. For the long sides of the tunnel, posts should be 10’ from each end (where the baseboards will meet) and 6” from the ends (to allow space for PVC ground posts). Attach the 2”x6”x10’ side baseboards to the pegs using 3½” screws, starting at one end (snug with the corner peg). For the end walls, place a peg 10’ from the outer edge of one of the sideboards, and 6” from each of the corners. Attach the first 2”x6”x10’ (snug against the end of the sidewall baseboard) and cut the second one to fit.

Figure 1. Baseboards laid-out ready for ground post installation.

4. Drive in Ground Posts. Mark inside of side baseboards at 3’ spacing starting from

the end of the sidewall baseboard. Remove corner pegs and string and drive in PVC ground posts at corners and at 3’ marks. Posts should go in roughly to the top of the baseboard, at most. It is possible to damage the PVC by hitting it too hard with the sledgehammer, or trying to force it through tight or stony soil. To avoid damaging PVC with the sledgehammer, have a helper hold a length of 2”x4” over the end of the pipe, and pound on the 2”x4”. The helper should wear gloves to protect against jolts.

Note: Our procedure calls for driving 3' PVC posts into the ground after laying out the baseboards. However, in shallow, tight or stony soils, it may be necessary to dig hole using an augur, and then set the posts in concrete. If it is likely that you will need to do this, then posts should be set before laying out the baseboards.

Figure 2. Ground posts ready to be driven in.

Figure 3. Ground posts damaged during pounding. This can be prevented by pounding on a 2"x4" rather then directly on the PVC pipe.

5. Hoop Assembly. Assemble 30’ hoops and purlin by gluing together 10’ and 20’ PVC

pipes. Use PVC primer and glue, following instructions for correct use of products.

Figure 4. Hoops being placed in ground posts.

6. Raising Hoops. Erect hoops by inserting one end into a 2” PVC ground post, and

bending the hoop to insert into the ground post opposite on the other side of the tunnel. Make sure that ends of hoops extend well into the ground posts (at least 12”). After inserting the posts, make minor adjustments in the height of the hoops (sight along the top of the hoops from a ladder) so that all are at the same height. Drill through baseboard and pipes with ¼” wooden drill bit. Attach using carriage bolts, washers and nuts, pushing the bolt through from the outside, and tightening the hoops snug to the baseboard

Figure 5. Drilling through baseboard, ground post and hoop. Carriage bolts will hold hoop in place.

7. Purlin Attachment. Attach purlin (30' 1½ PVC pipe) to the inside of the hoops. Drill

through purlin and hoops at 3’ spacing, and attach using carriage bolts, washers and nuts. Head of the bolt should be up to present a smooth surface to the poly that will cover the tunnel. We put a piece of duct tape over the top of the carriage bolt before putting the poly on the hoops.

Figure 6. Tunnel with purlin and hip board in place.

8. Hip Board Attachment. Attach hip boards at 3’ height using 1½” screws. Mark

hoops 3’ above baseboard, and attach 1”x4”x10’s end to end, starting at one end of the tunnel. Ends of hip boards may be secured together where they meet by screwing a block of wood across the inside of the junction.

Figure 7. Hip board in place.

9. End wall Construction. Use 2”x4” lumber to frame in end walls. There is no hard and fast rule for end wall design. However the attached picture shows our general design consisting of four uprights reinforced by horizontal and diagonal bracing. Spacing door uprights at a standard distance (32”, 34” or 36”) accommodates standard door sizes. Cut notches in the uprights to fit the inside of the baseboard or the hoop, and attach using 2½” or 3½” screws.

Figure 8. Tunnel showing end wall design at K-State Research and Extension Center, Olathe, Kansas.

Figure 9. Tunnel showing end wall design at Full Circle Farm, Kansas City, Kansas.

10. End wall Bracing. Attach end wall bracing. Cut 2”x4” lumber to run from baseboard

close to the second hoop, and attach to end wall and baseboard.

11. Plastic Preparation. Attach furring strips end to end along the upper half to the hip

boards. Alternatively attach the channel for wiggle wire using self tapping screws.

12. Plastic Attachment. It is best to do this on a calm day. Lay out the poly lengthwise

on one side of the high tunnel. If you are cutting from a longer roll of plastic, be sure to leave 2’ extra on each end to allow for attaching to the end walls. Pull plastic over the tunnel. A simple way to do this is to secure a rope close to the edge of the poly at each end of the tunnel by placing an object such as a tennis ball under the plastic and tying the rope around it through the plastic. Then the rope is thrown over the tunnel and the plastic pulled over the tunnel using the rope. Make sure the plastic is well centered on the tunnel and then attach by placing furring strips over the plastic, snug against and just below the furring strips already attached to the hip board. Attach the furring strips with 1½” screws, placed every 2 or 3 feet. Pull the plastic tight and attach to the other side in the same way. Finish securing the plastic by attaching to the end walls using additional furring strips. Note, you may also use poly tack strips (commercially available).

Figure 10. Poly attachment to hip board using one furring strip. This method is less secure than others since poly tends to tear at the screws.

Figure 11. Picture showing the 2-furring strip method of attaching poly to the hip board.

13. Roll-up Side Installation. Attach roll-up sides. Assemble top rail pieces to roll up

sidewall plastic with. Make sure the pipe is longer than the tunnel on both ends so that you can attach a handle to it, and to avoid difficulties with rolling up sides. Attach the pipe to the poly. We have used duct tape for this, but a better option is to use special clips for attaching poly to pipe, which are available from commercial sources. An alternative is not have roll-up sides at all, but to simply tie up poly when ventilation is required. This is easily done by placing eye-hooks in the hip board at each hoop, and running a piece of string below the sidewall poly, around the hoop and back. Both ends of the string are tied to the eye-hook. For roll-up sides, various options are possible, figure 8 shows a PVC crank that we have used.

Figure 12. Poly attachment to hip board using wiggle wire.

14. Stabilize Sidewalls. Prevent sidewalls from billowing. To prevent sidewalls from flapping in the breeze, some sort of support is needed to help keep them in check. Pieces of used drip tape running from the hip board to the baseboard at each hoop is effective for us. Using a fender washer along with the screw prevents screws from tearing though the drip tape in high winds

Figure 13. A drip tape strip from hip board to base board at each hoop can keep side walls from billowing.

15. Install plastic on the end walls. Since we take off the end wall plastic during the

summer months, we use a lower thickness end wall plastic. Either commercially available poly tack strip or furring strips may be used to secure a sheet of plastic completely over the end wall. Then a hole may be cut for the doorway.

For more on suppliers go

to: Resources

16. Frame Door. You can make a door, or use an old door on one or both ends of the

tunnel.

17. Shade Cloth Installation. Shade cloth helps keep temperature down during the

summer in high tunnels. In hot years, we put ours on from Memorial Day to Labor Day. Grommets sewn into the cloth every three feet allow for tying down to eye hooks fixed into the baseboards. We skew the shade cloth toward the south in order to provide better shading on that side.

About the Authors

Robbins and Jim Hail own and operate Bear Creek Farm in Osceola, Missouri.

Katherine Kelly owns and operates Full Circle Farm in Kansas City, Kansas.

Katherine Kelly in her newly constructed hoop house.

Ted Carey, Extension Specialist Food Crops, Kansas State Research and Extension Center Olathe, Kansas.

Building the KSU high tunnel

High tunnels are unheated greenhouses used to extend the growing season. In Kentucky they can allow year-round vegetable production.

In 2005-06 we erected a 30' x 40' high tunnel at the Kentucky State University research farm, using a frame salvaged from a heated greenhouse. The following pictures show the construction process. A table showing the cost of materials is at the bottom of the page.

Click a picture to see a larger view. Click here for a detailed examination of the effect of this tunnel on microclimate.

September 6,

2005September 7, 2005

Untreated 2x4s

were painted to

protect the end wall

framing studs.

Organic standards

do not allow treated

wood to come in

contact with the soil

or crop.

A screen door frame was built to fit inside metal hoops

salvaged from a used heated greenhouse.

September 8,

2005September 13, 2005

End walls included

4' x 4' window

frames.

Metal hoops were screwed to each end wall, then

aluminum wiggle wire track was attached to the upper

edge of each hoop with metal screws.

September 13,

2005September 13, 2005

The summer cover

crop of cow peas

was incorporated

into the soil at the

construction site.

Cowpeas were

chosen as a heat

tolerant cover crop

that would add

nitrogen and

organic matter to

the soil.

Anchors of galvanized steel pipe, welded to angle iron,

were pounded 2' into the soil to support each end wall.

September 13, September 15, 2005

2005

End wall frame

struts were bolted

to the anchor posts.

Workshop participants at the KSU farm field day attached

interior hoops to anchor pipes. Anchor pipes had been

pounded at an angle, with a wooden block between the

pipe and sledge hammmer to prevent the pipe end from

splaying.

September 24,

2005September 24, 2005

Completed tunnel

frame.

Frame structural details. Top: End wall struts supported

by angle iron and anchor pipe. Bottom: Pipes joined by

brackets (left) and sleeves (right).

December 7, 2005 December 7, 2005

Recycled plastic 1x6

toe boards were

A 60 W blower fan was attached to a hoop, and through

the inner plastic layer. Hoses were attached at the corners

attached around the

house perimeter. A

strip of 2x2 ran the

length of the house,

2' above the soil

surface. Aluminum

wiggle wire was

screwed to the end

wall toe boards and

the side wall 2x2.

Two layers of 6 mil

plastic were draped

over the frame, and

attached to the end

hoops with wiggle

wire.

of the house to allow air to pass between the side walls

and end walls.

December 7, 2005 December 7, 2005

Two layers of end

wall plastic were

attached with

wiggle wire

(foreground).

Attaching plastic to the frame took about three hours on a

calm afternoon.

January 18, 2006 January 25, 2006

An 8' wide paving

stone pad was laid

atop gravel and

sand at one end of

the house. An 18"

wide path was

constructed down

the center of the

house. Feather meal

fertilizer (Nature

Safe, 10-2-8) was

incorporated into

the soil with a roto-

tiller at 100 lbs N

per acre, and three

beds were formed

on each side of the

center path.

Six-week-old lettuce and kale seedlings were transplanted

on one-foot centers.

January 27, 2006 March 2, 2006

Lettuce, beets,

radish, and spinach

were direct-seeded.

Right bed: Transplanted kale (foreground) and lettuce

(background). Left bed: Direct-seeded greens.

March 21, 2006 February 2006 - June 2007

Ready for harvest!

Left bed:

Transplanted lettuce

(foreground) and

kale (background).

Right bed: Direct-

seeded greens.

Temperatures inside and outside the high tunnel.

Cost of high tunnel materials

Material CostExpected life

(years)$ per year

¢ per square

foot per year

Salvaged hoops

(estimated value)

Wiggle wire & track

Paving stones

Plastic boards

Screen doors

Lumber

Fasteners

Paint

Fan

Plastic

$1,020

$250

$380

$300

$250

$160

$60

$30

$100

$660

20

20

20

10

10

10

10

10

10

4

$51.00

$12.50

$19.00

$30.00

$12.50

$16.00

$6.00

$3.00

$10.00

$165.00

4.3¢

1.0¢

1.6¢

2.5¢

1.0¢

1.3¢

0.5¢

0.3¢

0.8¢

13.8¢

Total $3,210 $325.00 27.1¢

The plastic accounted for only 20% of the up-front cost, but will account for more than half of the cost amortized over time. The value of crops harvested should exceed the up-front material cost in the first year.