the how and why of plant selection for bmps: a hydrologist’s perspective scott dierks, pe

The How and Why of Plant Selection for BMPs: A Hydrologist’s Perspective

Scott Dierks, PE

June 13, 2013

Talk Outline• Why discuss plants? Aren’t they just decoration?• Refuting the notion plants are just “add-ons”

• Starting with how we do things, and moving to:• How a complete ecological system does things

• Understanding plants as design elements• Selecting plants• Seeding, planting & maintenance

How We Do Things• In 1900 60% of Americans lived in rural areas (USDA estimate).• In 2005 83% of Americans live in urban/suburban areas.• By 1986 over 69 million acres converted to urban/suburban landscapes

(53x the size of Delaware)• 30-40 million acres (62,500 mi2) in suburban lawn• Over 4 million miles of paved, public roads

• Est. total paved area in the US = 43,480 square miles = 5.5 x the size of New Jersey

Source: Stu Schwartz, Univ. of Maryland at Baltimore

Un-disturbed Lands: Forests & Woodlands 1.03 g/cc

Residential Land1.69 to 1.97 g/cc

Golf Courses; Parks; Athletic Fields1.69 to 1.97 g/cc

Concrete 2.2 g/cc

Impacts of “Soil Abuse”

How Plants Do Things• There is a feedback loop

between biotic & abiotic components of soil.

• Plant roots & bacteria release secretions that bind inorganic soil together into aggregates

• Exudates fuel biological activity, such as nutrient and pollutant cycling.

• Micro-aggregates are also bound together by root hairs, roots and fungal hyphae

• Changes in pore size distribution are made by roots, burrowing animals and dying roots

X-ray Computed Tomography of upper soil column

• Comparison of 24 side by side studies of cultivated land – row crop, pasture and turf grass vs un-cultivated land – ag buffers, restored and remnant prairies and forests

• Same taxonomic soil series for each paired study

• Data for A/B soil horizons for approximately 0-12-in depth

Aerenchyma

Understanding Plants as Design Elements

What is the target hydrology?

Water Balance Modeling

(1985)

Determine hydroperiod/innundation/drawdown time

Source: www.semcog.org/LowImpactDevelopment.aspx.

Source: www.semcog.org/LowImpactDevelopment.aspx.

These plants are tolerant of fluctuating water levels in this range. They will tolerate short periods of innundation, not to exceed 48 hours.

Planting Recommendations• Diversity is relative to the size of the BMP• < 200 Sq. Ft. - 5 species• 200 Sq. Ft. – 1500 Sq. Ft. = 6 – 9 species• 1,500 Sq. Ft. - 10 – 20 species• Landscaped appearance – 3 ft. O.C.• Naturalized appearance – 1 ft. – 2 ft. O. C.• How to calculate the number of plants:

• A/D² = # of plants• Where A = planting area in square feet• Where D = distance between plants on center (feet)Example: A 500 sq.ft. rain garden planted with plugs at 2 feet O.C.

500/2² = 125 plants

Developing a Planting Plan• Plant groups – submerged, emergent, mesic, upland• Consider height of mature plants

- Plant taller species toward back• Plant species that are adapted to the specific environmental

factors- Determine hydroperiod/innundation/drawdown- Is the site sunny or shady?- Are portions of the site exposed to salt spray/runoff?

• Select plants that bloom at different times and/or different colors

• Mass similar plants – helps with growth and aesthetics

Make sure you get Pure Live Seed (PLS) Can cover large areas more efficiently Usually includes a cover crop – annual

oat or rye Slower to establish 2 -3 years Often combined with plugs or gallon

stock Sold as mixes or can custom order $700 - $1300 per acre You lose control of what species get

planted and exactly where they go Typically do not seed permanently

innundated areas

Seed

Plants• Plugs

- 2.25” x 5”- From $1 - $3.50 per plug- Installs quickly- Faster start than seed

• Gallon containers- $4 - $6 per gallon- Older than plug plants- Faster establishment than plugs

Trees and Shrubs

• 5 gallon size - $18 -$25 each• Ball and Burlap 4 ft – 6 ft - $60 -

$80 each• Ball and Burlap 2 in diameter at

breast height (dbh) - $100 - $300

Maintenance• Even landscapes planted with natives require some maintenance,

particularly for the first two years after planting.• Invasives are typically primed to invade disturbed sites, hence the need for

early vigilance.• Typically first-year’s maintenance is built into the installation contract with a

guarantee to meet a threshold survival criteria, e.g., 80% coverage• Hand-pulling, targeted spraying, mowing before invasives go to seed and

prescribed burning are excellent ways to fight invasives and foster native plant growth1. http

://chesapeakestormwater.net/training-library/design-adaptations/stormwater-bmp-maintenance/

2. http://www.stormh2o.com/SW/Articles/Maintenance_of_Stormwater_BMPs_3287.aspx

3. http://rfcd.pima.gov/pdd/lid/pdfs/41-wa-spu02-020023.pdf

Other Plant Selection ResourcesWHAT TO PLANTIndiana Native Plant and Wildflower Society (INPAWS):

http://www.inpaws.org/ Indiana Wildlife Federation – Native Plants of Indiana:

http://www.indianawildlife.org/wildlife/native-plants/ Porter County Landscaping Standards and Guidelines, Recommended Plant

Lists:http://www2.porterco.org/uploads/media/Section_19_-_Appendix_01.pdf

Cardno JFNew Nurseryhttp://www.cardnojfnew.com/Nursery.aspx

WHAT NOT TO PLANT!Indiana’s Most Wanted List (Purdue University):http://extension.entm.purdue.edu/CAPS/browsePest.html

Source: San Mateo County Sustainable Green Streets and Parking Lot Guidebook

How we could do things better together

Questions?Scott.Dierks@cardno.com