Georgia Gardener Newsletter Design Tip: August 21 2008

Rain Gardens

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Georgia Native Joe-Pye Weed

Water quality as it relates to runoff has become an increasing problem in urban and suburban areas. When it rains, water runs off impervious surfaces (parking lots, roads, roofs, etc.) rather quickly carrying with it silt, trash and all the chemicals of modern living. These pollutants contaminate the very streams and rivers from which we get our drinking water. In an attempt to slow the movement of water and trap harmful pollutants, developments often build retention/detention ponds. This may solve the problem for larger areas, but our individual propeties face the same problem on a smaller scale.

Every landscape has at least one (or both) of these situations: an area where water runs as it heads downhill or a low area where water collects and takes several days to drain. In the past most people addressed the problem by creating a route for the water to quickly leave their property and continue downhill by using dry stream beds, French drains, etc. That was fine unless you happened to be the homeowner at the lowest point in the neighborhood making you the recipient of everyone else's runoff.

Then came the drought...

With water for the landscape in very short supply and when it does rain these days, it seems to come all at once, people started looking at ways to retain the water that fell or crossed their properties. Rain gardens are a simple, attractive and natural way to slow and capture runoff on your property and to help it slowly seep into the ground while retaining the pollutants that are carried with it. This is a win-win situation increasing the amount of water available to your landscape and cleansing the water that passes through on its journey to our creeks and rivers.

Rain gardens can be a simple as a small low area near your downspouts to beds dug down to capture the runoff from your driveway or yard all the way to large areas constructed to receive heavy amounts of runoff from commercial sites. There a quite a few web sites that discuss in detail the design and building of a rain garden:

Rain Garden Network
Georgia Clean Water Campaign
Athens-Clarke County (9.8MB pdf)

Shade & Sun Rain Gardens Images Courtesy of Diane Minick at Stormwater Landscapes, LLC

Because of the nature of rain gardens, the plants used need to be able to withstand periodic flooding, wet soil and in times of drought, bone dry conditions. They should also be chosen based upon their sun requirements. One item that I would like to stress is that I prefer rain gardens to be planted with native plants. Using native plants not only deals with the runoff issue, it provides habitat for the plants and other wildlife.

Woody Plants for a Sunny Rain Garden

Virginia Sweetspire (Itea virginica) Smooth Witherod (Viburnum nudum)

Virginia sweetspire is a common landscape shrub with several cultivars ('Henry's Garnet','Little Henry','Merlot') that is a tough-as-nails plant. I have rescued wild sweetspire from mucky ditches with standing water yet have seen it growing fine on dry commercial hillsides. The plant produces hanging finger-like clusters of white flowers in May. The new growth has reddish stems and the fall color (bright crimson) rivals any burning bush. This shrub also suckers making it a great plant for erosion control. Like Virginia sweetspire, smooth witherod is a water and drought tolerant blooming shrub. Blooming with other viburnums in April, it produces flat clusters of white flowers that give way to dark blue fruit in the summer that is loved by birds. Fall color is a spectacular orange-red. The cultivar 'Winterthur' can be found in nurseries.

Summersweet (Clethra alnifolia) Winterberry (Ilex verticillata)

At this time of year, summersweet is easy to see blooming in landscapes and in the wild in the southern half of Georgia. This plant makes its natural home in low wet areas and is commonly seen growing in roadside ditches and at the edges of streams and lakes. Summersweet produces upright clusters of white to pink flowers that attract butterflies and hummingbirds. I have seen this plant growing happily in standing water and in dry landscapes. It's also fairly shade tolerant. There are quite a few cultivars including 'Ruby Spice','Hummingbird','Sixteen Candles', etc. Winterberry is an average looking deciduous holly until it drops its leaves in the fall. Female plants are covered with bright red berries that attract birds. Make sure to plant a male winterberry nearby for pollination.

Other woody plants for sunny rain gardens: red maple (Acer rubrum), black willow (Salix nigra), river birch (Betula nigra), sycamore (Platanus occidentalis), buttonbush (Cephalanthus occidentalis), bald cypress (Taxodium distichum), inkberry (Ilex glabra), southern wax myrtle (Morella cerifera), sweetbay magnolia (Magnolia virginiana), yaupon holly (Ilex vomitoria), etc.

Perennials for a Sunny Rain Garden

Mixed with any of the woody plants above are a plethora of native flowers that grow great in wet to dry conditions in a sunny location.

Ironweed (Vernonia spp.) White Turtlehead (Chelone glabra)

Ironweed is just about to begin its blooming season. This majestic plant blooms after the Joe-pye weed at the top but is often found growing in similar conditions along creeks and roadside ditches. The dark purple flowers attract a wide range of butterflies. Often listed as not being drought tolerant, this summer has shown that established plants are still growing beautifully in areas that have been dry almost all year. Turtlehead is often found growing in moist shaded areas along creeks and in low woods. However, I can attest from first-hand experience that this plant will grow in full sun. This plant is also a late summer bloomer that attracts pollinators and reproduces easily from seed.

Swamp Sunflower (Helianthus angustifolius) Scarlet Hibiscus (Hibiscus coccineus)

As the name implies, swamp sunflower is usually found growing with its feet in the water but it tolerates dry periods which only serves to make it shorter. This is the last warm season perennial to bloom in my garden starting in early October. The wild species can get 10 or more feet tall but dwarf cultivars such as 'First Light' and 'Low Down' are available. In moist to average conditions, this plant is a colonizer. Scarlet hibiscus is a native to the southern part of Georgia but does fine throughout the state. It blooms in June and July with 8-inch scarlet red flowers that attract hummingbirds. This plant also gets tall, so plant accordingly.

Other perennials for sunny rain gardens: swamp milkweed (Asclepias incarnata), rosemallow (Hibiscus moscheutos), sweetflag (Acorus spp.), sedges (Carex spp.), northern sea oats (Chasmanthium latifolium), virgin's bower clematis (Clematis virginiana), hardy ageratum/mistflower (Conoclinium coelestinum), snakeroot (Eupatorium rugosum), blueflag irises (Iris versicolor, I. virginica), blue lobelia (Lobelia siphilitica), and beebalm (Monarda didyma) among others.

Shady Rain Gardens

If your rain garden happens to be located in part to full shade, you still have lots of options. The construction techniques will be the same, but the plants will be a bit different.

Woody plants for a shady rain garden: summersweet (Clethra alnifolia), Virginia sweetspire (Itea virginica), Florida leucothoe (Agarista populifolia), spicebush (Lindera benzoin), American hornbeam (Carpinus caroliniana) and silky dogwood (Cornus amomum).

Perennials for a shady rain garden: cinnamon fern (Osmunda cinnamomea), royal fern (Osmunda regalis), netted chain fern (Woodwardia areolata), sensitive fern (Onoclea sensibilis), foamflower (Tiarella spp.), green and gold (Chrysogonum virginianum), cardinal flower (Lobelia cardinalis) and the annual jewelweed (Impatiens capensis) among others.

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