Rain Gardens are landscaped areas strategically located to intercept stormwater runoff. They are slight depressions in the landscape, either natural or excavated, that can be planted to wild flowers and other native vegetation or to any moisture loving plants. Rain Gardens collect runoff from rooftops, lawns, driveways and parking lots and allow it to soak into the ground. Any pollutants such as sediment, fertilizer, pesticides and even oil, grease and heavy metals from roadways are trapped by the soil and root systems, allowing clean water to infiltrate the subsoil and recharge the groundwater.
Unlike bog or wetland gardens, Rain Gardens hold water from a few hours to a few days following a rain storm. Compared to a conventional lawn, a Rain Garden can allow 30% more water to soak into the ground. This helps prevent flooding and drainage problems while protecting our streams and rivers from harmful pollutants. Rain Gardens are also wonderful habitat for wildlife and can be an attractive asset to any property.
1. Site Selection and Layout
- How large an area do you want to commit?
- Stay at least 10 to 15 feet from foundations to prevent water in basement.
- Likewise stay away from septic system lateral fields.
- Determine your property lines. Consider a side garden in cooperation with your neighbor.
- Avoid right of ways and underground utilities – call 811 for utility locates before you dig!
- Locate an area where you can intercept runoff or a low area in your yard, but not where water stands for long periods.
- Consider directing downspouts to the garden area.
- Where will overflow go during large storms? Do not change the general drainage pattern or affect neighboring properties.
- Avoid excavating under large trees. You do not want to disturb the roots and the trees may not tolerate the added water.
- How will you integrate the garden into the existing landscape?
- Full sun is best – most native species prefer at least ½ day of sun.
- Size according to roof area: garden area should be 15-20% of roof area in sandy soils, 20-30% of roof area in silty soils and 60% of roof area in clay soils.
- Dig an 8” X 8” hole to test the drainage. Fill the hole with a bucket of water. The water should go down at a rate of 1 inch per hour.
- Water should only stand in a rain garden from a few hours to 1-2 days.
2. Construction
- Garden should be 2 to 8 inches deep with the average being 4 to 6 inches. If you have poor infiltration, make the area shallower to spread the water out over a larger area. Likewise, good infiltration allows for a deeper garden.
- The bottom of the garden should be flat with the sides sloping gradually towards it.
- Incorporate organic matter into the bottom to increase infiltration.
- Direct downspouts to the garden using swales or underground pipe.
3. Planting
- Select plants that can withstand periods of water inundation followed by dry periods.
- Consider using native plants which are tough and will survive extremes in temperature and precipitation. They have deep root systems which allow for better infiltration. They also attract birds and other wildlife.
- Rain gardens contain 3 zones - very wet, wet to dry and dry. Plant accordingly and move if necessary.
- For a neater appearance, select low growing plants and keep edge neatly trimmed.
- Mulch with coarse shredded hardwood that won’t wash away.
- Supplement moisture until plants are established.
4. Maintenance
- Do not use fertilizer. Native plants do not require fertilizer and we are trying to remove contaminants, not add them!
- Weed and mulch as necessary.
- You may need a few strategically placed rocks to break the flow where water enters the garden.
- Do not park or drive on garden. Compaction will greatly decrease infiltration.
- Do not let soil, sand or debris flow into garden.
- Move plants as necessary to provide optimum growing conditions.
Websites
-City of Lawrence -Includes good general information. http://clean-water.uwex.edu/pubs/index.htm -University of Wisconsin Extension
publications. www.critsite.com/index.cfm/fuseaction/plants.search/cfid/2351996/cftoken/32399905/index.htm -Excellent resource for plant selection. www.maplewoodmn.govoffice.com/ (type Rain Garden in search box) -Includes seven rain garden designs. www.danewaters.com/private/raingarden.aspx -Offers several links to other Rain Garden sites. www.rainkc.com/GARDENS/INDEX.ASP -10,000 Rain Gardens site for Kansas City area. http://dnr.wi.gov/runoff/rg/rgmanual.pdf -Rain Gardens- A how-to manual for
homeowners – excellent resource. www.pca.state.mn.us/publications/manuals/stormwaterplants.html -Publication: Plants for Stormwater Design
Plants for the Rain Garden
Natives– Other suggestions-
Rose Turtlehead Chelone obliqua Hostas
Yellow Coneflower Ratibida pinnata Sedums
New England Aster Aster novae-angliae Salvia
False Indigo Baptisia lacteal Yarrows
Blazing Star Liatris squarrosa Daylilies
Cardinal Flower Lobelia cardinalis
Wild Iris Iris shrevei
Blue Flag Iris Iris versicolor
Brown-eyed Susan Rudbeckia triloba
Joe Pye Weed Eupatorium maculatum
Sneezeweed Helenium autumnale
Blue Lobelia Lobelia siphilitica
Marsh Milkweed Asclepias incarnata
Sullivant Milkweed Asclepias sullivantii
Butterfly Milkweed Asclepias tuberosa
Spider Antelopehorn Asclepias asperula
White Penstemon Penstemon albidus
Sedges and Rushes-
Tussock Sedge Carex stricta
Blunt Spike Rush Eleocharis obtuse
Needle Spike Rush Eleocharis acicularis
Torey’s Sedge Juncus torreyi
Grasses-
Little Bluestem Schizachyrium scoparium
Side-oats Grama Bouteloua curtipendula
Prairie Drop Seed Sporobolus heterolepis
Prairie Cord Grass Spartina pectinata
Shrubs -
Black Chokeberry Aronia melanocarpa
Compact American Cranberrybush Viburnum trilobum ‘Bailey Compact’
Plant Sources Local Nurseries and Garden Centers Prairie Nursery
800-476-9453 www.prairienursery.com Kaw River Restoration
Nurseries 785-542-3090 krrn@appliedeco.com Prairie and Wetland Center 816-331-9738 www.critsite.com Prairie Moon Nursery
866-417-8146 www.prairiemoon.com Plant Sources Local Nurseries and Garden Centers Prairie Nursery
800-476-9453 www.prairienursery.com Kaw River Restoration
Nurseries 785-542-3090 krrn@appliedeco.com Prairie and Wetland Center 816-331-9738 www.critsite.com Prairie Moon Nursery
866-417-8146 www.prairiemoon.com