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A newsletter by the Renville County Master

Gardeners containing USDA Zone 4 appropriate

information Volume 138 June 2020

Meet the Renville County Master Gardeners

Louise Schweiss

Anderson–Fairfax; Joy Clobes - Fairfax

Teide Erickson - Winthrop Sandy Feldman –

Renville,

Cathi Fesenmaier –

Olivia; Erin Grams – Hector;

Susan Haubrich –

Danube;

Betsy Hennen –

Olivia; Jan Howell – Olivia;

Pam McColley -

Franklin;

Linda McGraw –

Buffalo Lake;

Beth O'Keefe – Morton;

Marie O'Keefe –

Morton

Barbara Stone-

Renville

The University of Minnesota is committed to the policy that all

persons shall have equal access to its programs, facilities, and employment without regard to race, color, creed, religion,

national origin, sex, age, marital status, disability, public assistance status, veteran status, or sexual orientation

RENVILLE COUNTY FAIR

CANCELLED

Visit us on Facebook at:

Extension Master Gardeners - Renville County

Master Gardener Meeting

Meeting on hold currently.

Inside this Issue:

June Garden Tips – Page 2

Good Options for Trees to Replace Ash - Page 3,

Clover Mites are Active Now- Page 5

Trees with Great Bark -Page 6

What to do about Eastern Tent Caterpillars - 8

Pretty, but aggressive Squill – Page 9

I Would Like to Plant Asparagus-Page 10

What’s Happening – Page 11

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“Gardening is about enjoying the smell of

things growing in the soil, getting dirty without

feeling guilty, and generally taking the time to

soak up a little peace and serenity.”

Lindley Karstens

This Photo by Unknown Author

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June Garden Tips ▪ Look for bare or drab areas in your yard that would benefit

from some annual color. Use annuals to mask declining

spring bulbs and early blooming perennials. Consider adding

a pot of annuals to the patio, deck, or entranceway.

▪ Don't forget your sunscreen, hat, sunglasses, and gloves when

you head out to the garden. You'll be protecting your skin and

eyes from UV rays and your hands from cuts and scratches.

▪ If you accidentally dig up bulbs when you're planting

perennials and annuals, just pop them back in the ground.

Replant them even if they're divided in half.

▪ Now is the time to mulch. Use pine needles, shredded leaves, and other organic material as mulch. A

thin layer (1 to 2 inches) of mulch helps conserve moisture, moderate soil temperature, and reduce

weeds.

▪ Remove flowers – deadhead – as they fade. Pinch or cut the flowering stem back to the first set of leaves

or flower buds. Use a knife or garden shears to make a clean cut. This improves the plant’s appearance

and encourages continual bloom

▪ Questions about your yard or garden? Ask Extension: http://www.extension.umn.edu/garden/ask/. In

Renville County, we have several trained Master Gardeners to answer your questions. Contact the

Renville County Extension Office at 320-523-3713 leave a message. Master Gardeners will return your

call.

Source: “Month-By-Month Gardening Minnesota & Wisconsin” by Melinda Myers

This Photo by Unknown Author is licensed under CC BY-NC-ND

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Good options for trees to replace ash BY: Matthew Russell is an UMN

Extension specialist in forest resources

Looking for a tree to plant in place of your ash? Here are seven good options Minnesota celebrates Arbor Day on the last Friday in April. The state celebrates Arbor Month during the entire month of May. Many Minnesotans like to celebrate this season by planting a tree. The emerald ash borer (EAB) has left behind many dead ash trees across Minnesota. All Minnesota counties have at least one variety of ash, and ash is found on 4.3 million acres in the state. Maybe the ash tree in your yard was taken down recently because of damage from EAB. Or maybe you have hundreds of ash trees in your woodland and you’re thinking about which tree species could replace them. Minnesota forests are home to three native ash species. • Black ash is the most common ash tree in Minnesota and is commonly found in forested wetlands. • White ash is common in mesic forests throughout central and southern Minnesota. • Green ash is more common on upland sites.

Unfortunately, all these ash trees are susceptible to EAB. Here are seven native tree species in parts of Minnesota that you can consider for replacing your ash. Each species has its own unique characteristics and are adapted to different sites.

Accolade elm is a disease-resistant variety.

American elm (the disease-resistant ones) Best reason to plant: You will bring back a charismatic tree to Minnesota’s landscape. You may be thinking did not all the elms die from a disease about 50 years

ago? Yes, they did! But an incredible amount of research and testing have provided a number of disease-resistant elm trees. These elms have been planted widely across Minnesota. In Minnesota’s forests and woodlands, elm and ash trees have historically been found in remarkably similar growing conditions. Both species can tolerate wet conditions. Elms are slightly different in that they require full sun for the best growth. Consult your tree or nursery supplier for suggestions on the right variety for the qualities that you want in an elm. The Valley Forge and Princeton varieties are most like the native American elm and have the

classic vase-like form when mature. Several hybrid Asian elms tend to be shorter in height compared to other varieties and grow well on tough sites.

Quaking aspen is a tree that sprouts vigorously and may replace ash.

Aspen Best reason to plant: You want to maintain trees in an ash woodland. All of Minnesota’s trees in the Populus genus — trees like quaking aspen, big-toothed aspen, and balsam poplar — may be good alternatives in woodlands formerly dominated with ash. Quaking aspen is the most common

tree in Minnesota today, making it a good choice to replace ash. Balsam poplar may do well in wetter soils, while quaking and big-toothed aspen may do better on drier sites. In fact, you may not need to plant aspen in a woodland if the species is close by. Aspen sprouts vigorously, a form of reproduction without using seeds. It is often one of the first species to come back to

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an area after a timber harvest or fire. Forest managers in northern Minnesota have been successful with planting cuttings from balsam poplar in black ash wetlands.

Northern white cedar

Extension Educator Mike Reichenback plants a northern white cedar along

Lake Superior’s North Shore.

Best reason to plant: You want a conifer that’s characteristic of the Minnesota Northwoods. Northern white cedar is an iconic tree that is a part of northeastern Minnesota. In its natural habitat, it can form dense stands and survives well in moist soils. If you are looking for an ornamental variety, it is sold under the name arborvitae. Northern white cedar trees will attract wildlife, especially white -tailed deer. Cedar is one of the most heavily browsed tree species by deer. Any choice to plant cedar will need to be immediately followed up with protecting seedlings. Ideally this would happen with fencing around trees

or groups of trees. Stands of cedar are often used as deer wintering areas. Deer may congregate in these areas in the winter to avoid heavy snow depths in other open areas, such as those with deciduous trees.

Swamp white oak Best reason to plant: You want to plant a tree that’s predicted to do well in Minnesota’s future climate. Also known as bicolor oak, this species can tolerate heavy and wet soil which makes it a good replacement for black ash. While native only to southeastern Minnesota, swamp white oak is known as a climate change "winner" and has been planted with success in research trials in northern Minnesota. Swamp white oak does not grow as tall as bur oak and white oak, two similar species. The tree is also less susceptible to the oak wilt fungus compared to red oaks. The acorns on this tree will attract a number of wildlife species.

Hackberry Best reason to plant: You want a hardy shade tree that can survive a tough environment. Hackberry is a hardy tree that can grow in harsh urban environments. It can survive heat and drought or wind and ice, making it suitable for Minnesota’s climate. In its native habitat it can be found in floodplains and along rivers in the central and southern portions of the state. Its corky bark sets hackberry apart from other trees in Minnesota. Birds and other wildlife will be attracted to its berry-like fruits.

Silver maple Best reason to plant: You want a fast-growing tree that provides a lot of shade. Silver maple is one of the fastest-growing maples. It is common in southern Minnesota and grows into the north-central part of the state, typically along rivers. Silver maple is widely planted as a shade or ornamental tree. Its leaves are dark green on top and

“silvery” on bottom, giving the tree its name.

The copper-colored bark of river birch sets it apart from other trees.

River birch Best reason to plant: You want a stately tree for your yard in the Twin Cities Metro or Blufflands. Most birches across the world are found in cool climates and grow into the

boreal forest. River birch is a different kind of birch, it is adapted to warm climates as far south as Florida. It can thrive in floodplains and near stream banks that are sometimes flooded.

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The river birch can be a single- or multi-stemmed tree, making it a great tree to consider for the landscape around your home. Its copper-colored bark makes it stand out from other common trees.

Diversify Not sure which species to plant? Plant several! Diversifying your yard or woodland with a variety of species gives you reassurance that your landscape can survive future insect and disease outbreaks. Any decision about which tree to plant requires careful planning and thinking. For more options, Extension’s replacement trees for ash page can help you figure out which trees will grow well in your plant community. Many municipalities maintain a list of suggested replacement trees for ash, so check with your local city or county’s forestry division. Consult an arborist or forester for more advice to make sure you plant the right trees in the right spot.

Clover mites. Note the long first pair of legs. Author & Photo: Jeff Hahn, U of MN Extension

If you are finding tiny creatures in sunny areas of your home, you may be seeing clover mites. Clover mites are tiny arachnids, relatives of spiders and ticks, and are about the size of a pinhead. They are reddish or brownish in color. If you look closely, you will notice that the first pair of their eight legs is particularly long and conspicuous. Why are they here? During summer, clover mites feed on grass and clover. Fortunately, they are not

pests on these plants and are rarely noticed. You might see them around homes in the fall but they are more commonly found the following April and May. They can congregate on the outside of buildings in large numbers and have no problem getting inside because of their small size, especially around windows. They love being in the sun and are most common on the south sides of homes. Fortunately, clover mites do not harm people or our property. How to remove them You can physically remove small numbers of clover mites, e.g. with a vacuum or gently wipe them up with a damp cloth. Be careful to avoid crushing them as the can stain surfaces. Clover mites are a temporary problem that goes away on its own when the weather becomes warmer. For more information, see the University of Minnesota Extension's Clover mites.

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Season of Trees: A tree with great bark!

Heritage® River birch

The Minnesota Landscape Arboretum is all about trees. And this tree, the river birch, is a marvel with its heavily peeling bark, excellent wildlife value, and land conservation importance. Plant breeders are finding new varieties to work in smaller yards, or large and majestic ones with excellent fall color. Plus, we will tell you about our favorite river birch at the Arboretum!

River Birch River birch (Betula nigra), sometimes called black birch, water birch,

or red birch, is a medium or fast growing tree best known for its peeling bark which exhibits shades of orange, red, gray, or cream blended with brown. Grown in single-stem or clump forms, it is native from Minnesota to Florida. As its common name implies, river birch prefers moist soils, and is commonly found along stream banks or areas prone to occasional flooding. It does not tolerate drought yet is suited to hot conditions. In soils with high pH due to limestone, clay, or poor drainage, iron chlorosis causes the leaves to become a chartreuse color. As such, this species prefers soils on the acidic side, and has been planted on former mining sites in reclamation efforts.

Bark ranges in texture and color, providing year-round interest.

What is river birch? • Deciduous, leaves drop in the fall • Height: 40-70 feet tall, smaller cultivars available • Width: 40-60 feet, smaller cultivars available • Habit: upright, pyramidal to rounded • Ivory, tan, and cinnamon-colored peeling bark • Male flowers: hanging catkins, 2 to 4 inches long • Female flowers: erect catkins, 1/2 to 1-1/2 inches long • Leaves: bright green and shiny in spring and summer, yellow shades in the fall Best growing conditions ● Hardiness zone: 3 to 7, tolerates heat ● Growth is denser in full sun, but shade tolerant

Recommended soil properties:

• Soil pH: 6.5 or below • Sandy to clay soils • Moist to wet soils, tolerates poor drainage and some compaction • Intolerant to drought

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Have your soil tested by the UMN Soil Testing Lab before planting. The best ways to use your river birch For landscape uses, the river birch makes a beautiful specimen. Once mature, the shade provided is plentiful, as the species typically reaches 40 to 70 feet in height, with a spread of 40 to 60 feet. Recently introduced cultivated varieties are shorter and well suited to smaller yards. Adaptable to sunny or shady locations, fall color can be brief, but pleasing, with yellows ranging from butter to gold. In early spring, sap flows from birch like maples. Recently, horticulturists at the Minnesota Landscape Arboretum collected birch sap at the same time as sugar maples. The amount of sap was less per tree, but the quality of the syrup was good. This species is a must for bird, butterfly, and moth enthusiasts. Mourning cloak butterfly caterpillars feed on the foliage, as do Luna and cecropia moth caterpillars. The nectar also attracts eastern tiger swallowtail butterflies and hummingbirds. Several songbirds feed on seeds, and some birds use the canopy cover for nesting.

Common problems

Male catkins form in the fall (photo above) and mature in the spring.

River birch is often considered the toughest of all birch. It resists damage from the bronze birch borer (Agrilus anxius), and sometimes develops leaf spots in wetter years. Neither issue is considered deadly. In high pH soils, leaves become chlorotic, and trees can eventually die without

the supplemental addition of sulfur or iron. Visit What’s wrong with my plant? - Birch for a list of the most common pest problems in Minnesota. Cultivated varieties of River birch for MN Cultivated varieties are selected for size, color, and performance in Minnesota. We recommend buying from local nurseries, as Minnesota-grown plants are already adapted to our climate and soils, require less transportation and fuel costs, and are unlikely to introduce or spread invasive species from other parts of the country.

• Fox Valley® — glossy green foliage, compact oval growth habit, 10 feet tall and 12 feet wide at maturity

• Heritage® — glossy green foliage, oval growth habit, 50 feet tall and 35 feet wide at maturity • 'Shiloh Splash' — green with white-edged leaves, pyramidal upright growth habit, 30 feet tall and

15 feet wide at maturity • 'Summer Cascade' — green foliage, cascading growth habit, 8 feet tall and 12 feet wide at maturity

The above varieties are listed in the Plant Information Online database, which offers plant and seed sources throughout North America. Our favorite River birch at the Arb Though it displays iron chlorosis from high pH soil, this tree has held on for years and years. Located in our Pillsbury Shade tree collection, our river birch is quite the specimen. Though the leaves are a lighter

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chartreuse color, it has held on and seems proud of its unique look. Enjoy a rest in the shade when walking the grounds! River birch is on our Interactive Tree Trek map. To find one, click the layers icon in the top right, and add Tree Trek. The map will show you where to go and give you a little info to take with you! Author: Erin Buchholz, Integrated Pest Management Specialist, Minnesota Landscape Arboretum

What to do about eastern tent caterpillars

If you have a flowering fruit tree, like apple, chokecherry, crabapple, plum, and cherry, check it for silken tents

in the forks of the branches. This is the work of eastern tent caterpillars.

These caterpillars are bluish black with a yellow and white stripe running down

the top of their body. They are mostly smooth but do have hairs sticking out

along the sides of their bodies. They are two inches long when fully grown.

Eastern tent caterpillars on a small tree.

Photo: Jeff Hahn, UMN Extension

Are they harmful?

Healthy, well-established trees can tolerate eastern tent caterpillar feeding. Their

feeding, as well as the presence of their webs, is usually a cosmetic problem,

affecting just the trees’ appearance.

However, young trees, as well as unhealthy, stressed trees, are more susceptible to feeding damage and may

need to be protected.

Can I manage these caterpillars without a chemical?

A great method to deal with eastern tent caterpillars without pesticides is to wait until they have retreated into

their tents at the end of the day or when it is raining. Then pull out the webbing, along with the caterpillars.

Then dispose of them by burying or bagging them (only burn them if it is permitted where you live).

You can also ignore the caterpillars and do nothing. The goal is to protect your trees; if spraying does not help,

then it is best just to leave them alone. This is a good option if the trees are large and healthy and are not at risk

and/or the caterpillars are large (close to two inches long) and finishing their feeding.

What are the best pesticides to use?

If your tree is susceptible to damage, and spraying can help protect it (i.e. the caterpillars one inch or smaller),

then consider an insecticide. There are different residual insecticides that are effective against caterpillars.

Consider using a product that has a low impact on the environment, such as Bacillus thuringiensis, spinosad, or

insecticidal soap.

Bacillus thuringiensis is a particularly good product if the tree is flowering since it will not harm visiting honey

bees and other pollinators. If you use insecticidal soap, the product needs to directly contact the insects. There is

no residual activity so you may need to repeat the treatment. Both of these products are most effective against

small caterpillars.

For information about eastern tent caterpillars and other caterpillars, see Caterpillars on ornamental plants.

Author: Jeffrey Hahn, Extension Entomologist UMN

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PRETTY, BUT AGGRESSIVE SQUILL Pretty, but

COVID-19 Update: The Minnesota Landscape Arboretum

reopened in a limited capacity on Friday, May 1. As a key part of the University of Minnesota’s research and outreach missions, we have been working with University leadership on a phased approach to ensure visitor and employee safety as we welcome you back. Siberian squill. Photos by Erin Buchholz. By Erin Buchholz, Integrated Pest Management (IPM) Specialist at the Minnesota Landscape Arboretum

As spring continues, and more and more of our horticulture staff (myself included) are recalled

working, we are reminded of past struggles. One is the lovely and cheerful spring ephemeral Scilla siberica, or Siberian squill.

You might already realize from its name; this species is not native to Minnesota. Brought here as an

ornamental, it can be confused with our native blue harebell (Campanula rotundifolia) or prairie

blue-eyed grass (Sisyrinchium campestre). There are also some nonnative

lookalikes: Puschkinia scilloides (striped squill), Chionodoxa luciliae (glory of the snow)

and Hyacinthoides hispanica (Spanish bluebell).

Siberian squill is a bulb, and it readily propagates itself from seed and bulblets. Some even think it can grow from broken root fragments! Each plant can produce multiple flowers on separate stems or in small groups as a raceme. Each seed head can produce dozens of seeds which usually drop straight down from the parent plant.

What is to love? The blue hues that show up in early spring bring happiness to those of us waiting for something colorful to signal the change in season. It blooms early, and gradually goes dormant after the seeds mature in late spring, allowing us to enjoy other plants later in the year. Bees love it, too! It’s a tad amusing to see blue pollen color their legs and abdomen after a nice feeding.

What’s to hate? Uff da, that is a harsh word! It is not so much that we hate Siberian squill. Rather, we are more concerned for the plants we

cannot get established because of Scilla’s greedy real-estate

needs. Scilla growing in the middle of ground-cover juniper. I playfully put a couple of our horticulturists on the defensive when I

ask, “Why do you hate Scilla?” Paul Sotak oversees the Perennial Garden, where it has taken over

the understory of some blue beech trees. “I don’t hate it,” Sotak says. “It’s beautiful, but it’s very invasive. When it naturalizes too much, it’s difficult to get rid of.”

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The area under the blue beech is dry shade and sloped — a challenging site already. Sotak is looking forward to replacing Siberian squill with some sedges, which are becoming more popular in the

gardening world. Carex appalachica, Carex laxiculmis ‘Hobb’ Bunny Blue, Carex ‘Ice Dance’ and seersucker sedge will provide a soothing solution to our dry-shade problem

(assuming we can get the Scilla out).

Fernando Hernandez works with Minnesota-native plants in the Grace B. Dayton Wildflower Garden. Siberian squill has been a frustrating challenge for a while now.

“I work in more natural areas, and Scilla is noticeably choking out native plants,” Hernandez

explains. “I’d like to replace it with more of our native spring ephemerals and woodland plants. My biggest challenge is: do we nuke it and start from scratch, or should we try to salvage what is already there knowing that leftover bulblets may undo all our work?”

Two years ago, Hernandez and his team carefully dug out a 5-foot by 5-foot area of Scilla and tried

to replace it with a dense carpet of wild ginger. All that remains from that planting are two lonely

survivors of that ginger, and a large recolonization of Siberian squill. “A monoculture is not as exciting to look at,” he notes. Not one to promote the overuse of chemicals (herbicides), I am happy to work with Sotak, Hernandez and our other talented staff members to think of the most effective and safest ways to achieve needed results. While we’ve discovered digging and replacements aren’t that effective, we are exploring fewer toxic methods like black plastic to cook the soil and bulbs.

Should the time come for herbicide control, we will rely on our pesticide applicator training to ensure visitor, staff and wildlife safety. However, many professionals have found that herbicides are not

effective against Scilla due to the thick, waxy leaves and its tendency to go dormant just as it is

about to be sprayed. Therefore, I do not recommend herbicides for this pest. We are going to keep

fighting with our hands, tools and wits!

For more information, please visit University of Minnesota Extension. Any other questions,

please let me know at buchh006@umn.edu. I will do my best to help!

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I would like to plant asparagus. What do I need to know to grow them? Knutson, Crow Wing County Master Gardener Volunteer Y Asparagus is a perennial plant that comes back every year and one of the earliest producing vegetables in the spring. There are both female and male plants. As a rule, female plants produce larger spears and male plants produce larger amounts of smaller diameter, more uniform spears. Most of the newer hybrids are all male plants.

Choose your planting spot carefully, as a bed of asparagus can last at least 15 years. Plant them in a fertile, sunny, well-drained site with good moisture. Medium-textured sandy loam to loam soils will usually produce the highest yields. Asparagus plants have a deep root system that can go down at least six feet, so avoid planting them in shallow soils or those with wet soil conditions. They grow best in a soil with a pH of 6.5-7.0, so it would be a good idea to get your soil tested to see if you need to amend it. Most people plant asparagus from purchased crowns because it is easier, and you get a crop one year earlier than if you plant them from seed. Try to purchase crowns that are one year old. Plant them with the crown buds upward in a trench or furrow about 12-18 inches apart and 6-8 inches deep; then immediately cover them with 2-3 inches of soil to keep them from drying out. Continue to add soil as the shoots emerge until the furrow is filled by the end of the first growing season. Asparagus crowns will continue to enlarge both vertically and horizontally over several years so planting at the appropriate depth is critical. It takes three years to develop a large root system and maximum fern growth to support future spear production. It is important to make sure your plants have adequate soil moisture. Inadequate soil moisture during fern development can cause significant reduction in the next spring’s spear production and negatively affect quality and yield.

To harvest asparagus, leave the old ferns until spring before chopping or mowing them. After spears appear, harvest when they are 6-8 inches long. Snap spears off at the soil surface. Do not cut the spears because of the danger of damaging neighboring spears that have not yet emerged. Allow spears remaining after July 1st to develop into ferns. BY: Jennifer Knutson, Crow Wing County Master Gardener Volunteer

, Crow What’s Happening

In our area ; If you are interested in more information, contact a

Master Gardener or email the Renville County Extension

Office at mnext-renville@umn.edu

Need to contact us? Call the Renville County Extension Office at

320-523-3713, or e-mail us at mnext-renville@umn.edu

Monday – Thursday 8 a.m. to 4:30 p.m.

At the Minnesota Landscape Arboretum: For more information on what’s happening at the

For more information on what’s happening at the Arboretum, please visit

http://arboretum.umn.edu/gardeningclasses.aspx

MN Plants: Free Webinar Series Live 7-8 p.m. Thursdays, May 14-Sept. 10 Join local horticulture experts for a closer look at the plants that grow in Minnesota. Explore collections, backyards and gardens as you learn more about trees, perennials, edible plants, houseplants and more. Upcoming webinars include May 14: Plants for Specific Landscape Uses: Tough Plants, Cold-tolerant Annuals, Fragrant Plants & Edible Plants; May 21: Discovering Plants with Minnesota Roots; May 28: Growing Roses in Minnesota; June 4: Minnesota's Native Orchids. Webinar login, details and complete schedule

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