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WSU/Pend Oreille Extension introduced the Sense of Place series in 1999, with a focus on place-based stewardship education. Since 2001, a partnership with the Kalispel Tribe of Indians Natural Resources Department (KNRD) has supported this newsletter and allowed us to expand class offerings through EPA funding. Further staff support comes through Renewable Resources Extension Act (RREA). Our newest partner, sponsor of the Rain Garden Challenge, is the Pend Oreille Conservation District. Many thanks to our partners and to you, our readers, for your continued enthusiasm for "digging" into the natural history and culture ofthis part of the world.

Rain Garden Basics


(Adapted with permission from Rain Gardens: Harvesting Rainwater in the Pacific Northwest, by Gary Bock and Douglas Stienbarger,
WSU/Clark County Extension, full document available online at http://clark.wsu.edu/volunteer/ws/ws-raingardens.pdf)

Why Build a Rain Garden?

As more development occurs in the Pacific Northwest, rain pours off roofs, driveways, sidewalks, and other impervious surfaces into our streams and rivers, transporting pollutants such as fertilizer, oil, pesticides, and pet waste. Rain gardens keep runoff from leaving your yard and pollutants stay in the garden where they can be absorbed by plants. Rain gardens reduce flooding by limiting the amount of water transported directly to the stream during rainstorms. Rainwater infiltrates into the ground and replenishes ground water while helping diminish flooding in local streams. As an added bonus, a rain garden planted with the right types of plants attracts birds, butterflies, and bees.

Planning the Rain Garden

Think carefully about how the rain garden will function in your yard. Is the area sunny, shady, windy, or sheltered? Do you want to view the garden from inside your home or from an area in the yard? Consider the color and bloom time of plants incorporated into the garden. Generally, you obtain a better effect by planting taller plants toward the back and shorter plants toward the front. The rain garden should meld seamlessly with existing or planned garden features such as arbors, patios, picnic areas, and benches. Rain gardens work well with wildlife friendly features such as ponds, bird baths, and feeders.

Choosing a Location

Look for a relatively level site that is slightly downhill from your downspout(s) and at least 10 feet from the basement or foundation of the structure. Talk to your neighbor if the garden will be located on or near the property line. Do not locate a rain garden over a septic tank or its drain field. You should also mark the underground utilities even when digging the garden by hand. Shape the rain garden to your personal taste, but make sure rainwater will flow and pool where needed (flowing either aboveground, or via a buried flexible pipe connected to the downspout). Akidney or horseshoe shape may be best in the middle of the yard, while a long, narrow garden usually works best along a property line.

Testing the Absorption Rate of Your Soil

Before investing the time and expense of building a rain garden, test your soil to determine its suitability. Some soils simply drain too slowly to adequately infiltrate rainwater fast enough.Test your soil by digging a hole 6 inches deep. Thoroughly soak the ground around the hole and fill the hole completely with water. Water should drain completely from the hole within 24 hours. If it does not drain, the area will not support a rain garden. In this event, look for another site in your yard with better drainage, or plan on installing piping and a drainage layer to divert excess water elsewhere.

Determining Size

Almost any size rain garden will help remove pollutants from storm water, improve groundwater recharge, and reduce your impact on the environment. However, you can accurately size your rain garden by
following some simple guidelines. You will need to estimate how much area will drain into the rain garden, the general type of soil you have, and the slope of the land where the rain garden will be. (see http://clark.wsu.edu/volunteer/ws/ws-raingardens.pdf for calculations.)

Site Preparation

Define the edges of the garden, then dig the entire garden about 12 inches deep, angling the sides at a 45 degree or less angle. Make the main basin of your garden as level as possible. Use excess soil to create a berm around the downhill edge of the garden . Place an outlet in the berm (usually just a small dip in the edge of the berm) to drain excess water after a large storm. Next, determine how you will divert water from your downspouts to your rain garden. Corrugated plastic drain pipe provides the simplest method, although you may find it more interesting to construct a dry creek bed. Test your layout by running water through the downspout. Be certain the water runs smoothly through the stream or pipe and spreads evenly across the bottom of your rain garden without eroding the sides. Once satisfied with the layout and function of the rain garden, work 3 to 5 inches of compost into the soil over the entire garden. This aids stormwater infiltration and gives the plants a healthy start. Lay out the plants according to your plan and plant each one carefully. After planting, mulch the entire garden with wood chips 2 to 3 inches deep. Avoid bark dust since it will likely float away during a heavy rain storm. The large surface area of wood chips captures and holds pollutants, keeping them out of our streams and
lakes. Wood chips also reduce your garden’s water needs during the drier summer months.

Rain Garden Maintenance

Rain gardens require extra water during the first couple of summers to become established. Water thoroughly and deeply once weekly to encourage deep roots and vigorous growth. The garden also requires more weeding during establishment. Weeds decrease considerably as the garden becomes established. After each growing season, stems and seed heads can be left for winter interest, wildlife cover, and bird food. They should be cut back in the early spring to make room for new growth. As the rain garden becomes more established, the need for maintenance will decline and you can spend your time enjoying the benefits of your garden.

You Need to Know:

• Rain gardens do not hold water for more than a few hours, they are designed to absorb runoff.
• Mosquitoes require several days to hatch so rain gardens do not breed mosquitoes. In fact, they attract insects that control mosquitos!

Do’s and Don’ts:

• Do not place the rain garden over a septic system!
• Do not build your rain garden where water already ponds - runoff will not soak in.
• Do locate your rain garden where plants get partial sun - you can use a wider variety of plants.
• Do try to put your rain garden on flatter ground - you have to dig less!

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