Build a Rain Garden
There’s a new garden in town. It is (mostly) easy to install, looks good
year-round, requires almost no maintenance and has a terrifically upbeat impact
on the environment. No wonder rain gardens are such a great new gardening trend!
Storm water runoff can be a big problem in summer during heavy thunderstorms.
As the water rushes across roofs and driveways, it picks up oil and other
pollutants. Municipal storm water treatment plants often can’t handle the
deluge of water, and in many locations the untreated water ends up in natural
waterways. The EPA estimates as much as 70 percent of the pollution in our
streams, rivers, and lakes is carried there by storm water! By taking
responsibility for the rainwater that falls on your own roof and driveway, you’ll
be helping to protect our rivers, streams and lakes from stormwater pollution.
To reduce the excess water runoff, many towns are encouraging businesses and
homeowners to install rain gardens in their yards. Rain gardens are specially
constructed gardens located in low areas of a yard where storm water can collect.
The idea is to have the water naturally funnel to this garden. The rain garden
collects water runoff and stores and filters it until it can be slowly
absorbed by the soil. Rather than rushing off into a storm sewer or a local
waterway, the rainwater can collect in a garden where it will be naturally
filtered by plants and soil.
Installing a rain garden is easy.
You simply dig a shallow depression in your yard and plant it with native
grasses and wildflowers; things that are easy to grow and maintain in your area.
What makes a garden a rain garden? First, the garden will be designed with a low
spot in the middle to collect and absorb rain water and snow melt. This depression
can range from a few inches in a small garden, to an excavated trough that’s
several feet deep. Second, rain gardens are usually located where they’ll catch
the runoff from impermeable surfaces like sidewalks and driveways, or from gutters
and roof valleys. Third, rain gardens are usually planted with native wildflowers
and grasses that will thrive in tough growing conditions. Finally, rain gardens
are designed to channel heavy rains to another rain garden or to another part of
Your rain garden should be located at least 10 feet from the house. The garden’s
size and location depends on the yard. The ideal situation would
be to locate the garden in a natural depression. You also can funnel water
from downspouts on gutters into the garden. The soil should be well drained
so the water doesn’t sit in the garden for more than two days. A special
“rain garden” soil mix of 50 to 60 percent sand, 20 to 30 percent topsoil,
and 20 to 30 percent compost is recommended. You can dig this mixture into
the soil to depth of 2 feet before planting.
Once you’ve identified the new garden’s location, remove the sod and dig a
shallow depression approximately 6-inches deep. Slope the sides gradually from the
outside edge to the deepest area. Use the soil that you remove to build up a
slightly raised area on the lowest side of the garden. This berm will help contain
the stormwater and allow it to percolate slowly through the rain garden.
If your rain garden is no more than about 6-inches deep, stormwater will usually
be absorbed within a one- to seven-day period. Because mosquitoes require seven
to 10 days to lay and hatch their eggs, this will help you avoid mosquito problems.
Your downspout or sump pump outlet should be directed toward your rain garden
depression. This can be accomplished by a natural slope, by digging a shallow
swale, or by piping the runoff directly to the garden through a buried 4″ diameter plastic drain tile.
Plant Selection.. The final touch.
The most difficult part of building a rain garden (if it can even be called that)
can be plant selection. Plants need to be tough enough to withstand periodic flooding,
yet attractive enough to look good in the garden. Deep-rooted, low-care native
plants, such as asters, and tough non-natives, such as daylilies, are best. If
properly designed, the rain garden can consist of a blend of attractive shrubs,
perennials, trees, and ground covers. Planting strips of grass around the
garden and using mulch also can help filter the water.
New plants should be watered every other day for the first two weeks or so.
Once they are well established, your garden should thrive without additional watering.
Fertilizers will not be necessary, and only minimal weeding will be needed after
the first summer of growth.