Connected Sustainability | Rain Garden
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Rain Garden


What Is a Rain Garden?

Rain Gardens are saucer-shaped landscape depressions filled with moisture-loving plants.


Why create a Rain Garden?

A Rain Garden is an all-natural storm water treatment system that allows 30% more water to infiltrate the ground. Rain Gardens are Low Impact Development (LID) approaches to storm water management that are simple to create and maintain. They treat runoff pollution and recharge local groundwater. They survive drought seasons. They conserve water, improve water quality, protect rivers and streams and remove standing water. When properly done mosquito breeding is reduced and beneficial insects that eliminate pest insects are increased. A habitat is created for birds and butterflies. Rain Gardens enhance sidewalk appeal and decrease the potential for flooding.


Why do Rain Gardens work?

The Rain Garden design collects storm water runoff from roof drains and sheet flow.

Plants trap sediment, fertilizers, oil, grease, pesticides and metals, while roots absorb water and nutrients. Decaying roots form tunnels to help water and oxygen filter through soil.

Water filters through soil, replenishing the groundwater supply.

Overflow exits the garden much cleaner, improving downstream water quality.


What size is a Rain Garden?

Approximately 4-8′ deep and 5-10% the size of the surface area that generates storm water runoff. Some may be much larger or smaller. The exact size and form will depend upon your individual needs.


Where should it be located?

At the end of a drain spout or roof gutter, at least 10′ downhill from a building, in soil at least 24′ deep and on a slope of less than 12%.  Rain Gardens should not be built over buried utilities or a septic system or under existing trees.


Why choose native plants?

Native plants live longer and are more tolerant of local weather and soil conditions. They also attract native birds and butterflies. Native Tennessee species of shrubs, plants and trees perfect for Rain Gardens are common milkweed, green milkweed, lance-leaf coreopsis, purple coneflower, blue flag iris, bee balm, black-eyed Susan, tussock sedge, redbud, Virginia sweetspire, New England aster, tickseed coreopsis, alumroot, great blue lobelia, cardinal flower, cinnamon fern, blue phlox, Christmas fern, wood poppy, swamp mallow, tall ironweed, upland sea oats, butterfly bush, flowering dogwood, paw paw and dozens of others, depending on the Rain Garden’s exposure to sun.

Traditional annuals or seasonals may be planted above and around the dry margins of the Rain Garden for added interest or accents for transitions.

What’s needed to create a Rain Garden?

1. A variety of native plant species
2. Bark mulch, aged 12 months, non-floating (Sometimes river rock and/or smaller rock gardens may be used.)
3. Filter media comprised of
25% topsoil
50% coarse sand
25% shredded bark, wood fiber mulch, peat or other compost
4. 3/8 pea stone
5. crushed stone
6. Some gardens may require perforated pipe to prevent drainage/prevents overflow