Rain Gardens: A Way to Improve Water Quality in Your Community
Category: Plant Materials
What are rain gardens?
When rain falls on natural areas such as a forest or meadow, it is slowed down, filtered by soil and plants, and allowed to soak back into the ground. When rain falls on impervious surfaces such as rooftops, roads, parking lots and driveways, rain does not soak into the ground and storm water runoff is created. Stormwater runoff picks up pollution such as fertilizer, pesticides, sediment, motor oil, litter, pet and yard waste. In many Massachusetts towns, stormwater runoff does not go to a treatment plant. Instead, water and the pollution in it flows directly into storm drains, which eventually can deliver these pollutants to bodies of water.
Rain gardens are attractive, functional landscaped areas designed to capture and filter stormwater before it runs off into storm drains. They collect water in natural or constructed shallow vegetated depressions and allow it to soak into the ground slowly. This reduces the potential for erosion and minimizes the amount of pollutants flowing from a yard into a storm drain, and ultimately into our waterways. They may also be used as a buffer in shoreline areas to capture runoff from the home landscape before it enters a lake, pond, river or estuary.
Rain gardens use the concept of bioretention, a water quality practice in which plants and soils filter pollutants from stormwater. By reducing stormwater runoff, rain gardens can be a valuable tool to help protect our water resources. While an individual rain garden may seem like a small thing, collectively they produce substantial neighborhood and community environmental benefits.
By capturing runoff in shallow depressions and letting it soak into the ground, rainwater gardens also help recharge stores of groundwater in aquifers. Moreover, they filter out sediment and other pollutants by catching close to the first inch of runoff, which contains the highest concentration of pollutants. Rain gardens transform stormwater from a destructive carrier of pollution into a source of sustenance for plant and wildlife habitats: the plants thrive on nitrogen and phosphorus that is picked up, while their stems trap sediment. Rainwater gardens are being incorporated into many new and existing areas for their environmental benefits, as well as their natural beauty.
What makes a rain garden a rain garden?
A rain garden resembles a regular perennial garden or mixed border in many ways. It is designed with deep-rooted plants that come back year after year; it is pretty to look at; it often has lovely flowers, grasses, trees and shrubs. So what makes it different from any other perennial garden? There are certain qualities that make a rain garden unique:
- Rain gardens have a ponding area, but they are not ponds. They often are planted with wetland plants, but they are not wetlands (although you can design a rain garden that mimics a wetland).
- The garden absorbs and filters rain that would otherwise run off your property and down the storm drain.
- Many of the plants in the garden might be native to the region and have extensive deep roots that help the garden absorb rain. The native plants do not need special attention once they are established. Non-native plants may be used as long as they are also non-invasive and pest free.
- There is a bowl-shaped dip in the garden, which holds the rain while it soaks into the soil.
- The garden bed is prepared or sometimes replaced to a depth of up to two feet in order to relieve soil compaction and make the garden able to absorb water.
A garden that does not have rain directed into it from a hard surface of your property will still be a valuable asset. However, unless stormwater runoff is directed into the garden, it is not a rain garden. In addition to reducing and filtering stormwater runoff and increasing groundwater recharge, rain gardens provide many other benefits. They provide habitat for wildlife and, with the proper selection of plants, increase the number and diversity of birds and butterflies for those who enjoy watching them. Rain gardens provide an attractive and creative alternative to traditional lawn landscapes and require less maintenance because they do not need to be mowed, fertilized, or watered once established. They may also increase property values with creative landscaping designs.
Locating the rain garden
Place rain gardens near your home to catch runoff from your roof, or farther out in your lawn to collect surface water draining across your property. Examine your yard while it is raining to discover the drainage pattern on your property. Find out where runoff flows and locate areas where water collects. If the rain does not flow naturally to your chosen spot, you can install piping underground or send the rain along a constructed channel or swale. Typically, the largest sources of runoff are rooftops, paved surfaces, slopes, and compacted soils. Some helpful tips are listed below to help you determine the best location for your rain garden:
- Rain gardens should be a minimum of ten feet from your home and your neighbors’ homes, to prevent damage from water seepage.
- Rain gardens should not be placed over or near the drain field of a septic system.
- Because these areas are already poorly drained, rain gardens should not be placed in an area of your yard where water collects. They should be placed up-slope of these areas to reduce the amount of water that flows into them.
- Sunny or partly sunny locations are best for rain gardens, but shade gardens are possible.
- Rain gardens should be integrated with your landscape. They can have a formal or informal look based on your preference.
- Rain gardens should not be installed under large trees. Trees have extensive root systems that may be damaged in the garden excavation process. In addition, they may not be able to adapt to the extra moisture being held by your rain garden.
- Make yourself aware of underground service lines or utilities. Call “Dig Safe” at 1-800-344-7233 for information about underground utilities.
Consider how the rain garden will fit in the overall landscape when looking for a location. Determine if you want it near outdoor gathering places where the beauty of the plants can be appreciated. Look out of your windows to see what views the rain garden can provide. The rain garden is more than just a stormwater management tool; it will be an integral part of your landscape.
Once you select a location, you may decide to send additional water to this site. Use flexible plastic pipe to direct water from downspouts and collecting areas to the rain garden. Be sure to factor this additional water flow into your garden sizing calculations.
Soils and drainage
Rain gardens work best when constructed in well-drained or sandy soils, but they can also be installed on sites with less permeable soils such as clays. Your rain garden needs to be able to absorb the water coming off your roof and driveway. Sandy soils drain well, while clay soils may become waterlogged. If your soil is sandy, you may be able to simply loosen the soil and improve it with some compost to prepare your rain garden for planting. If your soil is clay, you will have more work to do. Even light clay soils may create drainage problems if a lot of water is directed to the rain garden. Soil removal and replacement may be needed if your soil is clay. The recommended soil replacement mix is 50-60% sand, 20-30% topsoil, and 20-30% compost. Be sure no clay is in your replacement soil.
You can test your soil’s infiltration rate by digging a hole 8 inches wide and 8 inches deep. Fill it with water and see how long it takes to sink in. The water needs to go down an inch per hour. If it takes longer than that, you will need to do additional site preparation to improve infiltration.
There are three signs of an impermeable soil:
- The site ponds water or remains saturated for several days after a storm event.
- The soil shows signs of being a wetland soil (gray soil with ribbons or areas of brown color) within 1 foot of the surface.
- Water poured in the test hole is still there after two days, provided it has not rained.
If you see any of these signs, your garden will need to be designed as a backyard wetlands garden, or another location should be selected. Otherwise, your site is suitable for a rain garden.
How large should the rain garden be?
Rain gardens can be large or small – the size depends primarily on the site drainage area. The volume of water collected will be roughly equivalent to the amount of rain falling on impervious areas draining to the garden location, such as driveways, rooftops, and lawns (if included in the drainage area). To determine the volume of runoff to be collected, first determine the square footage of the surfaces that will provide the flow into the garden. If a gutter downspout will run directly into the garden, the only information that you will need is the area of the roof that contributes to that gutter. Measure the footprint of your house (the area taken up by your house if you were looking down from above). Then estimate how much of this area actually contributes to the gutter downspout. In other words, if it were raining, what portion of the roof area would be contributing water to the garden? Next, divide this area by 6. This calculation sizes the garden to hold one inch of roof runoff in a garden 6 inches deep. For example, suppose a house has a footprint of 60 feet x 30 feet, or 1800 ft2. One quarter of the roof area contributes to the gutter near where the rain garden is to be built. Therefore, the contributing area would be 1800 ft2 x 0.25 = 450 ft2. This area is then divided by 6, so that the square footage of the rain garden would be 450 ft2 / 6 = 75 ft2. A nicely shaped rain garden might be 10 ft x 7.5 ft. However, you have the flexibility to make it any shape you want, as long as you approximate the size. With silty soils, the size can be increased about 50%. If the soils are clayey, the size can be increased up to 100%. This increase will provide the same amount of treatment as if your soils were sandy. If you are including runoff from driveways or lawn areas, be sure to calculate the square footage and add that to the total to get the correct size needed. Once you have determined the total drainage area for your rain garden, use the following chart to determine possible rain garden dimensions. Dimensions are given for ponding depths of 6 inches and 3 inches. A good rule of thumb is that the rain garden should be about twice as long (perpendicular to the slope) as it is wide.
| Drainage Area | Required Size of Rain Garden (6” deep) | Potential Rain Garden Dimensions (ft x ft) | Required Size of Rain Garden (3” deep) | Potential Rain Garden Dimensions (ft x ft) |
|---|---|---|---|---|
| 800 ft2 | 40 ft2 | 4x10, 5x8, 6x7 | 80 ft2 | 7x12, 8x10, 9x9 |
| 1000 ft2 | 50 ft2 | 5x10, 6x8 | 100 ft2 | 7x15, 10x10 |
| 1200 ft2 | 60 ft2 | 4x15, 5x12, 6x10, 8x8 | 120 ft2 | 10x12, 8x15 |
| 1400 ft2 | 70 ft2 | 5x14, 7x10 | 140 ft2 | 10x14, 7x20 |
| 1600 ft2 | 80 ft2 | 7x12, 8x10, 9x9 | 160 ft2 | 8x20, 10x16 |
| 1800 ft2 | 90 ft2 | 6x15, 7x13, 8x12, 9x10 | 180 ft2 | 9x20, 10x18, 12x15 |
| 2000 ft2 | 100 ft2 | 7x15, 10x10 | 200 ft2 | 10x20, 14x15 |
| 2500 ft2 | 125 ft2 | 8x16, 10x13 | 250 ft2 | 10x25, 13x20, 15x17 |
| 3000 ft2 | 150 ft2 | 10x15, 12x13 | 300 ft2 | 10x30, 15x20 |
| 3500 ft2 | 175 ft2 | 8x16, 10x13 | 350 ft2 | 14x25, 18x20 |
| 4000 ft2 | 200 ft2 | 9x20, 12x15 | 400 ft2 | 16x25, 20x20 |
| 5000 ft2 | 250 ft2 | 10x25, 13x20, 15x17 | 500 ft2 | 20x25 |
Installing the rain garden
Once you feel confident in the placement of the garden, lay out the shape to define where to dig. Outline the area of the proposed garden by spraying with non-toxic soccer-field paint. Another method is to lay a hose along the shape of the garden, then dig along the hose. This gives a nice flowing border to the garden area. Alternatively, you could simply choose a rectangle as the shape of your garden.
If the yard is fairly level, you can just dig out the bowl to the proper depth, which is 6 inches deep, or a couple of inches deeper if mulch will be used. If the yard is sloped, you may need to construct a small berm (mound) at the down-slope side of the garden to prevent the soil from washing away after a storm. Use the soil that was removed from the upslope side of the garden and add it to the down-slope side. The bottom of the garden should be fairly level to maintain the storage area inside the garden. Slope the edges of the garden, but do not make them too steep. Steep slopes tend to erode easily. Mulch or a ground cover will help to stabilize the soils.
If the selected area is lawn, you will have to remove the turf. Either you can use this in another area of your yard, or it can be composted to help improve your soils. If your soil drains well, simple soil preparation is all that is needed. Incorporate compost into the garden bed to improve the quality of the soil. If your soils are clay, soil replacement is probably in order. You may also want to add a reservoir of gravel at the bottom of the garden bed, or add tiles or an under-drain that leads to another area. This will avoid having your rain garden become waterlogged. The idea is to create a living sponge of soil, plants, roots and mulch, not a soggy bog.
Grade the surface of your prepared rain garden bed in such a way that the water entering it can spread out over a large flat area and soak into the soil. This may involve removing a lot of soil. When your ponding area is ready and the soil is nice and loose, it is time to plant. You can prepare a rain garden bed and then cover it with mulch until later; then, plant through the mulch. On the other hand, you can plant immediately, and then mulch the plants. The choice is yours. The sooner the plants are in, the faster your rain garden will become established.
Planting the rain garden
While rain gardens are a highly functional way to help protect water quality, they are also gardens and should be an attractive part of your yard and neighborhood. Think of the rain garden in the context of your home’s overall landscape design. When choosing plants for the garden, it is important to consider the height of each plant, bloom time and color, and its overall texture. Use plants that bloom at different times to create a long flowering season. Mix heights, shapes, and textures to give the garden depth and dimension. This will keep the rain garden looking interesting even when few flowers are in bloom. A small tree or a few flowering shrubs may be included in the rain garden if it is large enough. It is important to note that plants in a rain garden will have to tolerate fluctuating levels of soil wetness. Your rain garden will have a couple of different wetness zones in it. In the deepest part of the garden, you can put plants that withstand a couple of days of standing water at a time. In the shallower parts and on the edges, you can put more typical landscape plants. Drought tolerant plants can be planted on the perimeter. Many native plants make great candidates for the rain garden and are generally adapted to local growing conditions. Introduced ornamentals may also be used as long as they have no invasive characteristics or problem pests.
When laying plants out, randomly clump individual species in groups of 3 to 7 plants to provide a bolder statement of color. Make sure to repeat these individual groupings to create repetition and cohesion in a planting. This will provide a more traditional formal look to the planting.
Use container-grown plants with a well-established root system. Dig the hole for each plant twice as wide as the plant container and deep enough to keep the crown of the young plant right at the soil line, as it was in the container. After you put the plant in the ground, gently tamp the soil around the roots to eliminate air pockets. Water immediately after planting, and then water weekly, to a depth of several inches, until the plants are well established. After the first growing season, you should not need to water the plants unless there is a lengthy drought. Add mulch two inches thick, keeping it off the crowns of the plants. Use mulch that will not float away; hardwood mulch is best.
The following plants are some of those that are suitable for inclusion in a rain garden:
| Trees | |||||
|---|---|---|---|---|---|
| Name | Exposure | Moisture | Mature size | Bloom | Comments |
| Acer palmatum Japanese maple | Sun to part shade | Moist | 5’-25’ depending on cultivar | Not significant | Graceful small tree; green or red leaves, some with deeply dissected leaves; excellent fall color |
| Acer rubrum Red maple | Sun to part shade | Dry to wet | 40’-60’ | April | Shallow root system; attractive red flowers and fruit; tolerates moist or dry sites; red/yellow/orange fall color |
| Betula nigra River birch | Sun to part shade | Dry to wet | 40’ | Not significant | Tolerates wet feet or upland site; interesting catkins; beautiful peeling bark; yellow fall color |
| Carpinus caroliniana American hornbeam | Part sun to shade | Moist | 20’-30’ | May | Tolerates sun if soil is moist; tolerates periodic flooding; unique fluted silver-gray bark; yellow, red, or orange fall color |
| Cornus kousa Kousa dogwood | Sun | Moist to dry | 25’-30’ | June/July | Resistant to dogwood anthracnose; large white bracts appear after the foliage; reddish purple fall color |
| Magnolia virginiana Sweetbay magnolia | Sun to shade | Wet to moist | 15’-20’ | June | Large white fragrant flowers; small multi-stemmed tree; red berries; semi-evergreen; will tolerate wet soils |
| Nyssa sylvatica Tupelo | Sun | Wet to dry | 30’-50’ | Not significant | Tolerates seasonal flooding or dry, rocky uplands; blue-black berries taken by birds; brilliant scarlet fall color |
| Shrubs | |||||
| Aronia arbutifolia Red chokeberry | Sun to part shade | Dry to wet | 4’-10’ | May/June | White flowers with red stamens; bright red, edible berries persist in winter; salmon to scarlet fall color |
| Aronia melanocarpa Black chokeberry | Sun to part shade | Dry to wet | 3’-5’ | May/June | White flowers with red stamens; black berries persist in winter; dark purple-red fall color |
| Callicarpa americana Beautyberry | Sun to part shade | Moist | 3’-8’ | July/August | July/August |
| Clethra alnifolia Sweet pepperbush | Sun to part shade | Moist to dry | 6’-8’ | July/August | Very fragrant white or pink flowers; yellow fall color; butterfly nectar plant |
| Cornus stolonifera Red twig dogwood | Sun to part shade | Moist | 6’-8’ | June | White flowers; blue or white berries; red/maroon fall color; scarlet twigs in winter |
| Hamamelis x intermedia Hybrid witchhazel | Sun | Moist to dry | 12’-15’ | December/April | Winter bloomers in yellow, red or copper; in bloom for 4 to 6 weeks; many cultivars |
| Hamamelis virginiana Witchhazel | Sun to part shade | Moist to dry | 12’-15’ | October | Tolerates irregular flooding or dry sites; yellow fragrant strap-like flowers; yellow fall color |
| Hydrangea arborescens Smooth hydrangea | Sun to part shade | Moist to dry | 3’-8’ | June/July | Creamy white flowers on new wood; cv. Annabelle has large flower heads; cv. White Dome is a lace-cap type |
| Hydrangea paniculata Panicle hydrangea | Sun to part shade | Moist to dry | 5’-12’ | July/September | Large panicles of white flowers turn to pink by fall; blooms on new wood; many cultivars available |
| Hydrangea quercifolia Oakleaf hydrangea | Sun to part shade | Moist to dry | 5’-8’ | July | Pyramidal white flower heads age to mauve; large oak-shaped leaves with deep red fall color; shaggy reddish bark is attractive |
| Ilex glabra Inkberry | Sun to part shade | Wet to dry | 3’-6’ | Summer | Slow-growing evergreen; creamy-white flowers; tolerates wet soils; need male & female for berries |
| Ilex verticillata Winterberry | Sun to part shade | Wet to moist | 6’-10’ | June/July | White flowers; yellow fall color; need male & female for scarlet berries; tolerates wet soil |
| Itea virginica Sweetspire | Sun to part shade | Moist | 4’ | May/June | Fragrant white flowers; fall foliage garnet to purple |
| Leucothoe racemosa Fetterbush | Partial shade to shade | Wet to moist | 4’-6’ | May/June | White drooping flowers; evergreen leaves turn red/purple after frost |
| Physocarpus opulifolius Ninebark | Sun | Moist to dry | 8’-10’ | May/June | Cultivars are better than the species; ‘Diablo’ has purple foliage while ‘Dart’s Gold’ has yellow foliage; drought tolerant |
| Rhododendron viscosum Swamp azalea | Sun to part shade | Wet to moist | 6’-8’ | July/August | Intensely fragrant white flowers; bronze fall color |
| Sambucus canadensis Elderberry | Sun to part shade | Wet to moist | 6’-8’ | June/July | Large white flower clusters; ornamental, edible purple berries; fast-growing |
| Sambucus nigra European elderberry | Sun to part shade | Moist | 10’-15’ | June | Larger than S. canadensis; numerous cultivars with colorful foliage |
| Viburnum dentatum Arrowwood | Sun to part shade | Moist to dry | 8’-10’ | May/June | Creamy white flowers; blue berries; crimson fall color |
| Viburnum sieboldii Siebold viburnum | Sun to part shade | Moist to dry | 10’-15’ | May/June | Creamy white flowers are followed by bright red berries which change to black, relished by birds |
| Viburnum trilobum American cranberrybush | Sun to part shade | Moist to wet | 8’-12’ | May | White flowers; edible red berries; yellow-purple-red fall color |
| Perennials | |||||
| Amsonia hubrechtii Willowleaf Bluestar | Full sun to partial shade | Moist to dry | 18”-3’ | May/June | Trumpet shaped light blue flowers, delicate bottlebrush leaves give this plant an attractive, shrub-like appearance; leaves turn a beautiful yellow in fall |
| Andropogon gerardii Big bluestem | Sun | Dry to moist | 3’-5’ | August/September | Prairie grass with purple flowers; blue-green blades turn tawny in fall; tolerant of acid soil, sandy soil, flooding and drought |
| Aquilegia spp. Columbine | Sun to part shade | Moist | 2’ | May/June | Flowers attract hummingbirds and butterflies, elegant blue-green divided foliage |
| Asclepias incarnata Swamp milkweed | Sun | Wet to moist | 2’-4’ | June/July | Pink blooms in midsummer; butterfly nectar plant; monarch butterfly host plant |
| Aster divaricatus White wood aster | Part shade to shade | Moist to dry | 1’-3’ | September/October | Good for dry shade or moist woods; white flowers attract butterflies; attractive massed at woodland edge |
| Aster laevis Smooth aster | Sun | Moist to dry | 2’-4’ | August/October | Pale blue flowers attract butterflies; mildew free |
| Baptesia australis Blue false indigo | Sun | Moist to dry | 3’-5’ | May/June | Indigo-blue showy flowers on blue-green, compound foliage make a striking show; effect is shrub-like |
| Chelone glabra White turtlehead | Sun to part shade | Wet to moist | 2’-3’ | September/October | White snapdragon type flowers; good fall bloomer |
| Chelone oblique Pink turtlehead | Sun to part shade | Wet to moist | 1’-4’ | September/October | Pink snapdragon type flowers |
| Cimicifuga racemosa Bugbane | Part shade to sun | Moist | 5’-6’ | July/September | Bold woodland edge plant with white, wand-like blooms; handsome foliage |
| Coreopsis verticillata Tickseed | Sun | Dry to moist | 2’-3’ | June/July | Yellow mini-daisies are held above delicate mound of lacey foliage; slowly spreading to form a small colony |
| Dennstaedtia punctilobula Hay scented fern | Sun to part shade | Dry to moist | 1’-3’ | n/a | Spreads rapidly; fragrant, light-green foliage turns yellow in fall |
| Echinacea purpurea Coneflower | Sun | Moist to dry | 3’ | July/August | Pink petals surround a bronze cone; a butterfly magnet |
| Eupatorium maculatum Joe Pye weed | Sun | Wet to dry | 5’-8’ | July/August | Huge, dusty-pink flowers attract butterflies; good fall color |
| Eupatorium rugosum White Snakeroot | Part shade to sun | Wet to moist | 3’-4’ | September | Long lasting, fuzzy white flower clusters; cv. Chocolate has purple/brown foliage |
| Filipendula rubra Queen of the prairie | Sun | Moist | 4’-6’ | June/July | Prefers well-drained evenly moist soils but will tolerate wet soils; foamy clusters of tiny pink blooms. |
| Geranium spp. Perennial geranium | Sun to part shade | Moist to dry | 10”-18” | May/July | Many species and cultivars; colors range from white to pink to blue |
| Hemerocallis spp. Daylily | Sun to part shade | Moist to dry | 2’-3’ | Summer | Many colors; extend season with early, mid, and late blooming cultivars; drought tolerant |
| Heuchera spp. Coral bells | Part shade to sun | Moist | 1’-1.5’ | May/June | Pink, coral or white flowers on spikes, many cultivars with purple/silver mottled foliage |
| Hibiscus moscheutos Rose mallow | Sun | Wet to moist | 3’-5’ | July/September | Shrub-like plant; very large pink or white flowers; hummingbird nectar plant; can grow with roots in water |
| Hosta spp. Hosta | Part shade to sun | Moist to dry | 6”-3’ | Summer | Hosta come in many sizes and foliage colors; mostly grown for foliage, their flowers are quite attractive; remarkably drought tolerant once established |
| Iris siberica Siberian iris | Sun | Moist to dry | 3’-4’ | May/June | Many colors, foliage turns apricot yellow in fall |
| Iris versicolor Blue flag | Sun | Wet to moist | 2’-3’ | May/June | Deep blue blooms on attractive grass-like foliage; can grow with roots in water |
| Liatris spp. Gayfeather | Sun | Dry to moist | 2’-4’ | July/August | Tall stems carry purple flowers that open from the top down; foliage is grass-like; very drought tolerant |
| Lobelia cardinalis Cardinal flower | Part shade | Wet to moist | 3’ | August | Will grow in full sun if kept moist; brilliant scarlet flowers attract hummingbirds |
| Lobelia siphilitica Great blue lobelia | Part shade | Moist | 2’-3’ | August/September | Blue flowers remain in bloom for 3 to 4 weeks |
| Matteuccia pennsylvanica Ostrich fern | Sun to shade | Moist | 4’-5’ | n/a | Plants form colonies by underground rhizomes; tall, gracefully arching fronds |
| Monarda didyma Beebalm | Sun to part shade | Moist | 3’-4’ | July/August | Many cultivars available in a range of colors and mildew resistance; forms small colonies; attracts hummingbirds and butterflies |
| Osmunda cinnamomea Cinnamon fern | Shade to sun | Moist | 3’-5’ | n/a | Interesting cinnamon colored spore fronds appear in the center of the plant; needs constant moisture if in sun |
| Panicum virgatum Switch grass | Sun | Dry to moist | 3’-6’ | July/September | Many good cultivars available; tolerates flooding; airy seed heads in summer |
| Rudbeckia spp. Black eye Susan | Sun | Dry to moist | 2’-5’ | June/September | Many different species offer color through the season; both annual and perennial |
| Schizachyrium scoparium Little Bluestem | Sun | Dry to moist | 3’-4’ | August | Lovely native grass, blooms in August and turns buff/golden in fall; dense root system; tolerant of poor soils |
| Solidago spp. Goldenrod | Sun | Dry to moist | 18” – 4’ | July/October | Many species available; does not cause hay fever; great late season color |
| Tiarella cordifolia Foam flower | Part shade to sun | Moist | 1’ | May | Spikes of foamy white flowers in spring; forms a small colony |
| Groundcovers | |||||
| Ceratostigma plumbaginoides Leadwort | Sun to shade | Moist to dry | < 1’ | August/September | Shrubby groundcover spreads rapidly in loose soil; drought tolerant; brilliant blue flowers; leaves red in fall and spring |
| Chrysogonum virginianum Green and Gold | Partial shade | Moist to dry | < 1’ | May/June | Golden daisy-like flowers continue sporadically until frost; spreads easily |
| Epimedium grandiflorum Bishop's Hat | Partial shade to shade | Moist to dry | 1’ | May/June | Foliage remains green most of the year, once established it will tolerate dry conditions |
| Phlox subulata Moss Phlox | Sun to part shade | Moist to dry | < 1’ | April/May | Evergreen; flower colors range from blue to pink and white; forms mats |
Maintaining the rain garden
Just like any other garden, your rain garden will need some basic maintenance to keep it healthy and functioning.
- Mulch annually to suppress weeds and to keep soils moist, which allows for easy infiltration of stormwater; un-mulched surfaces may develop into a hardpan, which impedes water infiltration. Before applying new mulch, remove the old mulch. Alternately, loosen up the old mulch with a rake and just top dress it with new mulch. The depth of the mulch should never exceed 3”.
- Weed your garden, especially during plant establishment; newly planted species may have a tough time competing with weeds. Once plants become established, less weeding will be required.
- The plants in your rain garden will need to be watered regularly during establishment to ensure healthy growth. Once established, plants should be watered in long periods of drought. Water deeply once or twice a week; avoid frequent shallow watering.
- Keep your garden healthy and clean. Rain gardens should be periodically cleared of dead vegetation and any debris that may collect. Replanting may be necessary over time. If a plant is not doing so well in one location of the garden, it may have to be moved to a wetter or dryer area.
Enjoy your rain garden and your contribution to water quality in your neighborhood.
Written by: Roberta Clark
Revised: 08/2011
Adapted from:
- How Does Your Garden Grow: A Reference Guide to Enhancing Your Rain Garden.
LID Manual, Prince Georges County, MD, Dept. of Environmental Resources
- Rain Gardens: A Household Way to Improve Water Quality in Your Community.
University of Wisconsin Extension and Wisconsin Department of Natural Resources
- Rain Gardens: A How-to Manual for Homeowners.
University of Wisconsin Extension and Wisconsin Department of Natural Resources
- Backyard Rain Gardens.
North Carolina Cooperative Extension
