Showing posts with label water quality. Show all posts
Showing posts with label water quality. Show all posts

Planting a rain garden

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.