Beautiful and Beneficial Rain Gardens
By
Amy McDowell
Two raindrops are floating down the river,
destined to become drinking water in the next city. One has been filtered clean
by soaking through a rain garden. The other is carrying traces of animal waste,
pesticide and fertilizer residue from turf, and petroleum products from
pavement. Which one would you rather see pulled into the water treatment plant?
Rain gardens are beautiful and simple to
install. They improve water quality and provide wildlife habitat.
A rain garden is a shallow bowl-shaped
flowerbed planted with deep-rooted native flowers, grasses and sedges. When it
rains, runoff from hard surfaces like the roof and driveway collects in the
rain garden basin. The water then percolates down through the soil, and
pollutants are filtered out.
Six steps to installing a rain garden
1-
Choose a low spot at least 10 feet on a downward slope away from your home.
2-
Test your soil’s drainage by digging a hole 16 inches deep and 8 inches wide
near the center of your new garden. Pour 8 inches of water into the hole. If
the water goes down at least one inch every hour, your soil is in good shape
for a rain garden.
3-
Lay out a garden hose to design the shape of your bed and remove the sod.
4-
Loosen up the soil eight inches deep and amend it if needed. The best soil mix
for a rain garden is 50-60 percent sand, 20-30 percent topsoil, and 20-30
percent compost. That 2:1:1 ratio makes the best spongy soil for root
penetration and water absorption.
5-
Smooth and level the soil and spread shredded mulch over the surface.
6-
Install the plants, spacing them about a foot apart. This list of rain garden
plants is a good place to start for a pleasing mix of colors and textures. At
least one third of your plants should be grasses and sedges.
Rain garden plant list
Blue flag iris Iris virginica
Bottlebrush grass Hystrix patula
Bottlebrush sedge Carex comosa
Broom sedge Carex scoparia
Canada anemone Anemone canadensis
Cardinal flower Lobelia cardinalis
Great spike rush Eleocharis palustris
Marsh blazing star Liatris spicata
Marsh marigold Caltha palustris
Monkey flower Mimulus ringens
Nodding onion Allium cernuum
Spiderwort Tradescantia ohioensis
Swamp milkweed Asclepias incarnata
Sweet flag Acorus calamus
Turtlehead Cheylone glabra
Virgin’s bower Clematis virginana
Wood gray sedge Carex grisea
Buy plants in multiples so you can plant
them in drifts. A list of Iowa nurseries who sell native plants is available at
http://grandprairiefriends.org/nurseriesIA.html.
