Too Much Water Can Undermine Your Home

If you worry about a wet or damp basement, a busy sump pump, or muddy puddles in your yard after a heavy rainfall, this story is for you. We want to introduce you to a new tool to improve drainage— a rain garden.

A rain garden is basically a plant pond, that is, a garden bed that you plant with special deep-rooted species. These plants help the water rapidly seep into the soil, away from your house and out of your hair. You direct the rainwater from the downspouts to the garden via a swale (a stone channel) or plastic piping. The garden captures the water and, when properly designed, drains it into the soil within a day. You don’t have to worry about creating a mosquito haven; the water drains before mosquitoes even have time to breed.

If there’s an especially heavy rainfall, excess water may overflow the rain garden and run into the storm sewer system. Even so, the rain garden will have done its job. It will have channeled water away from your foundation and reduced the load on the sewer system. A rain garden also reduces the amount of lawn chemicals and pet wastes that may otherwise run off into local lakes and rivers. In some communities, the runoff problem is so big that homes with rain gardens qualify for a tax break! Call your municipality to learn your local policy.

In this article, we’ll tell you how to design, build and plant a rain garden suitable for your yard. We’ve condensed it to a few handy guidelines. You won’t need any special tools or equipment. A shovel and a level will do. But expect to sweat through some heavy digging!

Rain Garden Design and Benefits

Well-designed rain gardens are not only good for the earth, but good-looking as well By Adam Regn Arvidson

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A rain garden is a shallow planted depression designed to hold water until it soaks into the soil. A key feature of eco-friendly landscape design, rain gardens—also known as bio-infiltration basins—are gaining credibility and converts as an important solution to stormwater runoff and pollution. Here we’ll show you how to make a rain garden fit handsomely into a landscape and still fulfill all of its environmental functions.

Naturalized plantings, here camassia, can make a rain garden fit easily into its surroundings. Photo by: Rob Cardillo.

Nowadays, according to the EPA, much of the rain that falls on a typical city block heads overland to the nearest pipe, washing along any crud it finds. Historically that water would have infiltrated—soaked in—leaving impurities behind in the soil and plants as it passed through to replenish the water table. Rain gardens are intended to counteract both the unnatural runoff patterns in urban and suburban areas (too many roads, too much paving, too many hard surfaces) as well as the increased crud levels found in them.

Rain gardens can work in most climates, but are most effective in regions with a natural groundwater hydrology—that is, areas with deep soils that drink in water rather than rocky areas that force rain to run overland. Most of the United States is like this. Rain gardens have gained wide residential use in cities as diverse as Kansas City, Minneapolis, and Portland, Oregon (the latter two offer utility-bill discounts for rain-garden installation). Entire towns, such as Maplewood, Minnesota, have turned to rain gardens to handle neighborhood storm-water management, plunking little planted basins down between curbs and property lines.

Swaths of pennisetum and other grasses convert a large, shallow-draining swale into a textural garden. Photo by: Rob Cardillo.

More than a dozen rain-garden designs can easily be found on the Internet. Essentially, you dig a basin, plant some water-tolerant plants, mulch it in well, and redirect your downspouts to the hole. The online guides will tell you to locate a rain garden 10 feet from your house and at a natural low spot. That’s a good start, but your rain garden runs the risk of just floating out there, awash in lawn and disconnected from your bigger design picture.

RAIN GARDEN DESIGN TIPS

  • Think of a rain garden just like a border or foundation planting rather than a beloved specimen tree. In other words, it should not be a stand-alone feature.
  • Consider all the rules of composition, screening and circulation—not just the rule that says to put a rain garden in a low spot 10 feet from the house.
  • Pick a shape that works with the rest of your garden design. A rain garden does not need a specific shape to function properly so feel free to be creative.
  • A rain garden can be as formal or as wild as you like—it’s all about the plant selection. Monocultural rain gardens are OK as long as that fits with your overall design. Here are some favorite rain-garden plants: Lobelia cardinalis (cardinal flower), Iris versicolor or I. virginica (blue flag iris), Veronicastrum virginicum (culver’s root), Carex vulpinoidea (fox sedge), Cornus sericea (red-twig dogwood), Acorus gramineus (sweet flag), and Athyrium filix-femina (lady fern).
  • A rain garden doesn’t have to be separate from other plantings. Consider making a depression within a perennial bed or shrub border (especially if space is tight and you don’t have room for a larger rain garden that stands alone).
  • Put in more than one rain garden for repetition and continuity. If it works with your overall design, create a little rain garden for each downspout.

Biostream at Scott Arboretum, Swarthmore College, collects excess rainwater, slowly filtering and releasing it into the landscape. Planted with amsonia and Iris pseudacorus, which tolerate periodic flooding. Photo by: Rob Cardillo.

“So how can we get away from a rain garden being a kidney shape plopped in the front yard?” asks John Gishnock III. My thoughts exactly, because that result is pretty common. Gishnock is owner of Formecology, a design/build firm specializing in rain gardens and native plants in Wisconsin. He has created rain gardens that are seamlessly incorporated along typical suburban driveway-to-door sidewalks; gardens below dry-laid stone walls adjacent to rustic pathways; and even a garden in the shape of a spiral galaxy (to be viewed from a lucky owner’s second-story porch). “A rain garden,” says Gishnock, “needs to look like the rest of the landscape.”

Landscape architect Jim Hagstrom of Savanna Designs in Lake Elmo, Minnesota, agrees. “We integrate rain gardens into the design,” he says, “and two-thirds of the time you won’t notice them.” His designs depend mostly on his clients’ sensibilities. Some love the wild native look of a traditional rain garden, while others favor the idea of infiltration but don’t want to see a “patch of weeds.” He has incorporated a rain garden into the center of a circle drive and devised a standing stone flow-through curb to match the house. He has created a large basin that infiltrates most water then holds the rest for pond habitat. He has built rain gardens in the centers of lawns, by dishing the landscape and ensuring well-draining soil. “You get a little pond after a rain,” he describes, “and in 24 hours it’s gone, and you have the lawn back.”

Flowers of hot-pink primroses punctuate a streamside garden at Chanticleer, bringing a pop of color to the varied greens of other moisture-loving plants, such as hostas, iris, ferns, and dwarf scouring rush. Photo by: Rob Cardillo.

However they look, rain gardens work, helping to reduce storm-water waste by 99 percent, according to one study, and keeping runoff clean. But they can also be an integrated design element, making landscapes both sustainable and beautiful.

9 PLANTS FOR A RAIN GARDEN

Plant selection for a rain garden can be a challenge. In addition to the favorite plants mentioned above, landscape architect Jonathan Alderson used these 9 plants, among others, in a rain garden designed to solve drainage issues for a home being built in Wayne, PA. “The garden is the reason the house could be built,” states Alderson, referring to the dilemma that no building permits could be issued until there was a solution for the poor drainage.

Swipe to view slides

Photo by: Rob Cardillo.

1. Rudbeckia fulgida
Zones 3-9

With regular deadheading, orange coneflower will bloom from summer until frost with orange-yellow flowers on stems that reach 3 feet tall.

Photo by: Rob Cardillo.

2. Panicum virgatum ‘Northwind’
Zones 5-9

Switchgrass grown 4 to 6 feet tall, so it’s good for screening less-than-desirable views of the road. It spreads slowly by rhizomes.

Photo by: Rob Cardillo.

3. Physostegia virginiana
Zones 3-9

This light purple bloomer grows 3 to 4 feet tall. Hummingbirds like it, but deer do not. Obedient plant blooms from early summer to early fall and spreads by both seed and rhizomes.

Photo by: Rob Cardillo.

4. Monarda fistulosa
Zones 4-9

Wild bergamot is an herbaceous perennial that brings hummingbirds and butterflies to the garden. It’s light purple-pink blooms last from late June through the beginning of August.

Photo by: Rob Cardillo.

5. Ilex verticulata ‘Aurantiaca’
Zones 3-9

Most winterberries have red fruits, but ‘Aurantiaca’ produces orange-red fruits that fade to orange-yellow in autumn. It is dioecious, which means it needs a male plant in order for the female to produce berries. ‘Aurantiaca’ grows to 5 feet tall in full sun to part shade.

Photo by: Rob Cardillo.

6. Chasmanthium latifolium
Zones 3-8

The seed heads of northern sea oats are attractive and look good in arrangements. Here, they mingle with bright yellow Amsonia hubrichtii.

May seed aggressively in some situations.

Photo by: Rob Cardillo.

7. Lobelia siphilitica
Zones 4-9

Blue cardinal flower growers to 3 feet tall, and vivid blue flowers appear from midsummer into early fall. In open conditions with moist soils, it will self-seed.

Photo by: Rob Cardillo.

8. Amsonia hubrichtii
Zones 5-8

Bluestar has two seasons of color: spring, when it produces periwinkle blue flowers on 2- to 3-foot stems; and fall, when the foliage turns brilliant yellow. Plant it in multiples for the best effect.

Photo by: Rob Cardillo.

9. Solidago rugosa ‘Fireworks’
Zones 4-8

Landscape architect, Jonathan Alderson refers to ‘Fireworks’ as a “well-behaved” goldenrod, because this cultivar’s rhizomes spread more slowly than the rhizomes of other species. Rough goldenrod’s golden yellow, gracefully arching panicles bloom from September into October, providing ample nectar for bees and butterflies. ‘Fireworks’ grows to 3 feet tall.

Portions of this article were contributed by Therese Ciesinski

Soak Up the Rain: Rain Gardens

A rain garden is a depressed area in the landscape that collects rain water from a roof, driveway or street and allows it to soak into the ground. Planted with grasses and flowering perennials, rain gardens can be a cost effective and beautiful way to reduce runoff from your property. Rain gardens can also help filter out pollutants in runoff and provide food and shelter for butterflies, song birds and other wildlife.

More complex rain gardens with drainage systems and amended soils are often referred to as bioretention.

Note: Refer to the links in this section for important tips on how to locate your rain garden. These include areas to avoid and the need for accurate information about underground utilities before you begin to dig.

Information About Rain Gardens

Rain Gardens, Green Infrastructure, U.S. EPA

Bioretention Illustrated: A Visual Guide for Constructing, Inspecting, Maintaining and Verifying the Bioretention Practice, 2013, Chesapeake Stormwater Network (PDF) (95 pp, 7.8 MB, About PDF) Exit

Water-Smart Landscape Design Tips, Water Sense
Information about plant selection, soils, and maintenance.

  • What To Plant Database for native plants in your area

Woody Shrubs for Stormwater Retention Practices, Cornell University, 2014 (PDF) (56 pp, 33.2 MB, About PDF) Exit

Rain Garden Outreach and Communication How-to-Guide, Resource Media (PDF) (20 pp, 2.4 MB, about PDF) Exit

Local resources

  • Connecticut
  • Maine
  • Massachusetts
  • New Hampshire
  • Rhode Island
  • Vermont

Connecticut

Rain Gardens, University of Connecticut Exit
Information on siting and sizing a rain garden, design, installation and long and short term maintenance. Also includes a series of Frequently Asked Questions and a Cost Calculator for estimating the cost to install a residential rain garden.

  • Rain Gardens in Connecticut: A Design Guide for Homeowners, University of Connecticut Exit
    A colorful 12-page brochure introduces rain gardens and discusses how to plan and install them in the home landscape.

The Connecticut Native Tree and Shrub Availability List, Connecticut Department of Environmental Protection (PDF)(12 pp, 256 K, About PDF) Exit
A (January 2005) native tree and shrub availability list for locating native planting stock.

Native Plants for Landscape Use in Connecticut, Federal Highway Administration, U.S. Department of Transportation Exit

Resident’s Guide to Rain Gardens, Connecticut Department of Energy and Environmental Protection (PDF) (2 pp, 533 K, about PDF) Exit
Introduces rain gardens, including information about what they are, the benefits and some common questions.

Rain Gardens, Reduce Runoff.org, Connecticut Fund for the Environment, Save the Sound Exit
Defines rain gardens, collaboration with partners, some available tools and resources.

Top of Page

Maine

Adding a Rain Garden to Your Landscape, University of Maine Cooperative Extension Exit
Introduces rain gardens and includes instructions and plans on how to plan, design, install and maintain.

Top of Page

Massachusetts

Rain Garden Guide, Massachusetts Watershed Coalition (PDF) (5 pp, 806 K, About PDF) Exit
An introductory guide on how to site, design, plant and maintain a rain garden.

Community Guide to Growing Greener, Massachusetts Watershed Coalition (PDF) (65 pp, 2.1 MB, about PDF) Exit
Includes a listing of shrubs and trees suited for the area.

Bioretention Areas and Rain Gardens, Clean Water Toolkit, Massachusetts Department of Environmental Protection pavement Exit
Fact sheet includes graphics of rain gardens and bioretention along with basic descriptions of the practices and information about design, benefits and maintenance.

EPA, YouthBuild, Greenway Conservancy Build a Rain Garden in Boston, April 2012 Exit
Earth Day 2012 collaboration in downtown Boston

Top of Page

New Hampshire

How do I build a rain garden?, Soak Up the Rain New Hampshire, New Hampshire Department of Environmental Services Exit
Video documents the installation of a residential rain garden. Explains why we want rain gardens, factors to consider in determining site suitability and plant selection, and many other rain garden basics while demonstrating how to dig and plant a new rain garden.

Rain Garden Do-it-Yourself Fact Sheet, New Hampshire Homeowner’s Guide to Stormwater Management, Do-It-Yourself Stormwater Solutions For Your Home, Soak Up the Rain New Hampshire, March 2016 (PDF) (66 pp, 4 MB, about PDF) Exit
Refer to page 35 for the Rain Garden fact sheet for information about rain garden design and siting considerations, installation and maintenance instructions.

A Shoreland Homeowner’s Guide to Stormwater Management (PDF) (15 pp, 1.4 MB, About PDF) Exit
The guide describes practices, including rain gardens, that shoreland homeowners can install to reduce or prevent polluted stormwater runoff from their roofs, patios, lawns and driveways.

SOAK stories about rain gardens around the state, Soak Up the Rain New Hampshire, New Hampshire Department of Environmental Services Exit

Top of Page

Rhode Island

Rain Gardens, Simple Steps at Home, Rhode Island Stormwater Solutions, University of Rhodes Island Exit
Includes links to many fact sheets, including rain garden maintenance information for homeowners and professionals.

Bay-Friendly Living, Save the Bay (PDF)(19 pp, 15.1 MB, About PDF) Exit
Tips on how to make your yard more attractive, cut back on chores and improve the quality of your local waters. Includes information and links on planting a rain garden, selecting native plants (and avoiding invasives), and lawn care.

Rain Gardens and Bioretention around Rhode Island, LID Inventory, University of Rhode Island, Rhode Island Stormwater Solutions Exit

Rain Gardens: A Design Guide for Homeowners in Rhode Island, University of Rhode Island Cooperative Extension (PDF) (6 pp, 1 MB, about PDF) Exit

Rhode Island Wild Plant Society Exit
Information about native plants and native plant nurseries

Rhode Island Coastal Plant Guide Exit
A reference for those involved in the design and management of coastal landscapes

Top of Page

Vermont

Infiltration: Bioretention/Rain Gardens, Vermont Department of Environmental Conservation Exit
Some basics, along with photos and illustrations on design, sizing, placement, and installation.

Absorb the Storm – Create a Rain-friendly Yard and Neighborhood, Lake Champlain Sea Grant, University of Vermont Cooperative Extension (PDF) (24 pp, 2.5 MB, about PDF) Exit
Discusses a number of steps homeowners can take, including rain gardens, to help prevent the problems associated with runoff.

The Vermont Rain Garden Manual: “Gardening to Absorb the Storm”, University of Vermont (PDF) (20 pp, 2.3 MB, about PDF) Exit
This manual explains how to choose a location for a rain garden, choose plants, install and maintain the garden. Includes plant lists.

Vermont Low Impact Development Guide for Residential and Small Sites, Vermont Department of Environmental Conservation (PDF) (54 pp, 4.7 MB, about PDF) Exit
Discusses the benefits of rain gardens with instructions on siting, designing, and installing rain gardens.

Top of Page

As soon as it starts raining, I can’t help but think of all the ways I should be saving this precious resource. My son always suggests we catch the water by putting out a bunch of buckets, and I politely tell him that while that is a solution, there are more effective ways to use and save the water—and one of those is with a rain garden. Harvesting rainwater is a wise technique used for centuries, and as our water supply becomes increasingly vulnerable, we need to be thinking in these conservational, sustainable ways.

Please keep reading to learn if a rain garden could be a smart addition to your landscape:

What exactly is a rain garden?

Above: Landscape architect Christine Ten Eyck turned to an ancient technique for conserving water when she built check dams in tiered garden beds (shown) that are equipped to retain rain water and slow the flow of storm water. Photograph by Matthew Williams, from Curb Appeal: 10 Landscaping Ideas for a Low-Water Garden.

Rainwater infiltration gardens—also known as “rain gardens”—are a bit like a plant pond, or rather a bowl-like depression created in the landscape that slows storm water runoff and effectively collects it from impervious area, like roofs, driveways, and patios and then gives it the chance to be cleaned and slowly absorbed into the soil. Besides acting like a living sponge, a rainwater system also helps divert excess water from vulnerable building foundations. There are many designs possible but they all do the same action of capturing, channeling, and diverting water. And of course when it’s not raining, the garden can be a hub for wetland plants and pollinators, plus stones and rocks will suggest a peaceful, watery scene.

How hard is it to install a rain garden?

Above: Photograph via Ramsey-Washington Metro Watershed District.

Installing a rain garden isn’t difficult if you’re willing to get digging or you bring in machines to help. Most rain gardens are 8-inches deep but this depends on soil type and size of the garden. Also, doing some homework before the digging begins is essential. Start by asking your local Cooperative Extension Office for specifics about rain fall patterns, soil mixes, garden size, and native plants. Design tip: Ovals, kidneys, and amoeba shapes look and function best, but rain gardens can also be long and skinny if your site dictates that. Use a garden hose or rope to lay out possible shapes, and always keep your rain garden at least 10 feet away from foundations to avoid unwanted water collecting.

What plants are best in a rain garden?

Above: Some Carex species (sedges) require damp or wet conditions while others are relatively drought-tolerant. Carex appalachica, above, is native to woodlands in the eastern United States. Photograph courtesy of Hoffman Nursery, from Gardening 101: Carex

Ideally, choose plants native to your area, especially those found naturally occurring near creeks, in swamps, and in prairies that occasionally have to contend with flooding and droughts. Natives are adapted to local erratic water cycles and fortunately don’t crave fertilizers. Basically you want to create three zones: Zone one is the center part of the ring, perfect for a collection of plants that help take up excess water and accept standing water for a longer period of time: plants like native sedges, ferns, or here in California yellow monkey flower (Mimulus guttatus). Zone two is for plants that can stand occasional standing water like wild ginger (Asarum caudatum), and zone three is for plants that prefer drier feet like drought tolerant Salvias, Ceanothus, and Lupine. Remember to choose plants that bloom at different times and attract pollinators, and select a variety of plants to ensure a dynamic, attractive, and diverse rain garden.

How much maintenance do rain gardens take?

Above: A curbside swale captures rainwater in Portland, Oregon. Photograph landscape designer Kristien Forness, from Every Garden Needs a Wetland (Well, at Least in Rainy Cities).

The good news is that rain gardens are less maintenance than vegetable gardens, perennial beds, and lawns. Your time spent will mainly be on weeding, pruning ,and adding more nutrient rich compost to conserve moisture and suppress weeds. Tip: When doing maintenance in the basin, make sure to walk lightly to avoid soil compaction which inhibits proper filtering. Of course you will also need to monitor the nuts and bolts of the system: the downspouts, gutters, inlets (directs water from incoming runoff into the garden), outlets (controls water level in the rain garden and redirects overflow) to make sure nothing has disconnected or become clogged with dirt or leaf litter. A great time to do this is before and after each rainy season. The goal is to reduce your workload, not increase it.

Why are rain gardens important?

Truthfully, a rain garden will not miraculously solve every water issue you might have, but it is an effective and attractive method of managing and saving rainfall. And the benefits are numerous: The filtration action—thanks to plant roots and soil—improves water quality in nearby bodies of water and makes sure that rainwater soaks into the ground and becomes available for plants as groundwater rather than being sent through storm water drains straight out to sea. This process cuts down on pollutants reaching creeks and streams. Rain gardens can also be a cost-effective and beautiful way to reduce runoff, and prevent erosion and flooding of your property. And, of course, when planted properly, rain gardens can create excellent natural habitats for birds, butterflies and pollinators.

For more on water conservation, see:

  • Hardscaping 101: Rain Chains
  • 10 Easy Pieces: Rain Barrels
  • The Garden Decoder: What Is ‘Xeriscaping’?

All About Rain Gardens

What Is A Rain Garden?

A rain garden is a garden of native shrubs, perennials, and flowers planted in a small depression, which is generally formed on a natural slope. It is designed to temporarily hold and soak in rain water runoff that flows from roofs, driveways, patios or lawns. Rain gardens are effective in removing up to 90% of nutrients and chemicals and up to 80% of sediments from the rainwater runoff. Compared to a conventional lawn, rain gardens allow for 30% more water to soak into the ground.

A rain garden is not a water garden. Nor is it a pond or a wetland. Conversely, a rain garden is dry most of the time. It typically holds water only during and following a rainfall event. Because rain gardens will drain within 12-48 hours, they prevent the breeding of mosquitoes.

Why Is Rainwater Runoff A Problem?

Every time it rains, water runs off impermeable surfaces, such as roofs or driveways, collecting pollutants such as particles of dirt, fertilizer, chemicals, oil, garbage, and bacteria along the way. The pollutant-laden water enters storm drains untreated and flows directly to nearby streams and ponds. The US EPA estimates that pollutants carried by rainwater runoff account for 70% of all water pollution.

Rain gardens collect rainwater runoff, allowing the water to be filtered by vegetation and percolate into the soil recharging groundwater aquifers. These processes filter out pollutants.

What Makes A Rain Garden Different From A Traditional Garden?

In the design of a rain garden, typically six to twelve inches of soil is removed and altered with tillage, compost and sand to increase water infiltration. The type of alteration to the soil depends on the current soil type, so it is a good idea to obtain a soil test.

Rain gardens are generally constructed on the downside of a slope on your property and collect rainwater runoff from the lawn, roof and/or the driveway. Once water collects in the rain garden, infiltration may take up to 48 hours after a major rainfall. Also, rain gardens incorporate native vegetation; therefore, no fertilizer is needed and after the first year, maintenance is usually minimal.

Rain Gardens: A Way to Improve Water Quality

What are rain gardens?

When rain falls on natural areas such as a forest or meadow, it is slowed down, filtered by soil and plants, and allowed to soak back into the ground. When rain falls on impervious surfaces such as rooftops, roads, parking lots and driveways, rain does not soak into the ground and storm water runoff is created. Stormwater runoff picks up pollution such as fertilizer, pesticides, sediment, motor oil, litter, pet and yard waste. In many Massachusetts towns, stormwater runoff does not go to a treatment plant. Instead, water and the pollution in it flows directly into storm drains, which eventually can deliver these pollutants to bodies of water.

Rain gardens are attractive, functional landscaped areas designed to capture and filter stormwater before it runs off into storm drains. They collect water in natural or constructed shallow vegetated depressions and allow it to soak into the ground slowly. This reduces the potential for erosion and minimizes the amount of pollutants flowing from a yard into a storm drain, and ultimately into our waterways. They may also be used as a buffer in shoreline areas to capture runoff from the home landscape before it enters a lake, pond, river or estuary.

Rain gardens use the concept of bioretention, a water quality practice in which plants and soils filter pollutants from stormwater. By reducing stormwater runoff, rain gardens can be a valuable tool to help protect our water resources. While an individual rain garden may seem like a small thing, collectively they produce substantial neighborhood and community environmental benefits.

By capturing runoff in shallow depressions and letting it soak into the ground, rainwater gardens also help recharge stores of groundwater in aquifers. Moreover, they filter out sediment and other pollutants by catching close to the first inch of runoff, which contains the highest concentration of pollutants. Rain gardens transform stormwater from a destructive carrier of pollution into a source of sustenance for plant and wildlife habitats: the plants thrive on nitrogen and phosphorus that is picked up, while their stems trap sediment. Rainwater gardens are being incorporated into many new and existing areas for their environmental benefits, as well as their natural beauty.

What makes a rain garden a rain garden?

A rain garden resembles a regular perennial garden or mixed border in many ways. It is designed with deep-rooted plants that come back year after year; it is pretty to look at; it often has lovely flowers, grasses, trees and shrubs. So what makes it different from any other perennial garden? There are certain qualities that make a rain garden unique:

  • Rain gardens have a ponding area, but they are not ponds. They often are planted with wetland plants, but they are not wetlands (although you can design a rain garden that mimics a wetland).
  • The garden absorbs and filters rain that would otherwise run off your property and down the storm drain.
  • Many of the plants in the garden might be native to the region and have extensive deep roots that help the garden absorb rain. The native plants do not need special attention once they are established. Non-native plants may be used as long as they are also non-invasive and pest free.
  • There is a bowl-shaped dip in the garden, which holds the rain while it soaks into the soil.
  • The garden bed is prepared or sometimes replaced to a depth of up to two feet in order to relieve soil compaction and make the garden able to absorb water.

A garden that does not have rain directed into it from a hard surface of your property will still be a valuable asset. However, unless stormwater runoff is directed into the garden, it is not a rain garden. In addition to reducing and filtering stormwater runoff and increasing groundwater recharge, rain gardens provide many other benefits. They provide habitat for wildlife and, with the proper selection of plants, increase the number and diversity of birds and butterflies for those who enjoy watching them. Rain gardens provide an attractive and creative alternative to traditional lawn landscapes and require less maintenance because they do not need to be mowed, fertilized, or watered once established. They may also increase property values with creative landscaping designs.

Locating the rain garden

Place rain gardens near your home to catch runoff from your roof, or farther out in your lawn to collect surface water draining across your property. Examine your yard while it is raining to discover the drainage pattern on your property. Find out where runoff flows and locate areas where water collects. If the rain does not flow naturally to your chosen spot, you can install piping underground or send the rain along a constructed channel or swale. Typically, the largest sources of runoff are rooftops, paved surfaces, slopes, and compacted soils. Some helpful tips are listed below to help you determine the best location for your rain garden:

  • Rain gardens should be a minimum of ten feet from your home and your neighbors’ homes, to prevent damage from water seepage.
  • Rain gardens should not be placed over or near the drain field of a septic system.
  • Because these areas are already poorly drained, rain gardens should not be placed in an area of your yard where water collects. They should be placed up-slope of these areas to reduce the amount of water that flows into them.
  • Sunny or partly sunny locations are best for rain gardens, but shade gardens are possible.
  • Rain gardens should be integrated with your landscape. They can have a formal or informal look based on your preference.
  • Rain gardens should not be installed under large trees. Trees have extensive root systems that may be damaged in the garden excavation process. In addition, they may not be able to adapt to the extra moisture being held by your rain garden.
  • Make yourself aware of underground service lines or utilities. Call “Dig Safe” at 1-800-344-7233 for information about underground utilities.

Consider how the rain garden will fit in the overall landscape when looking for a location. Determine if you want it near outdoor gathering places where the beauty of the plants can be appreciated. Look out of your windows to see what views the rain garden can provide. The rain garden is more than just a stormwater management tool; it will be an integral part of your landscape.

Once you select a location, you may decide to send additional water to this site. Use flexible plastic pipe to direct water from downspouts and collecting areas to the rain garden. Be sure to factor this additional water flow into your garden sizing calculations.

Soils and drainage

Rain gardens work best when constructed in well-drained or sandy soils, but they can also be installed on sites with less permeable soils such as clays. Your rain garden needs to be able to absorb the water coming off your roof and driveway. Sandy soils drain well, while clay soils may become waterlogged. If your soil is sandy, you may be able to simply loosen the soil and improve it with some compost to prepare your rain garden for planting. If your soil is clay, you will have more work to do. Even light clay soils may create drainage problems if a lot of water is directed to the rain garden. Soil removal and replacement may be needed if your soil is clay. The recommended soil replacement mix is 50-60% sand, 20-30% topsoil, and 20-30% compost. Be sure no clay is in your replacement soil.

You can test your soil’s infiltration rate by digging a hole 8 inches wide and 8 inches deep. Fill it with water and see how long it takes to sink in. The water needs to go down an inch per hour. If it takes longer than that, you will need to do additional site preparation to improve infiltration.

There are three signs of an impermeable soil:

  • The site ponds water or remains saturated for several days after a storm event.
  • The soil shows signs of being a wetland soil (gray soil with ribbons or areas of brown color) within 1 foot of the surface.
  • Water poured in the test hole is still there after two days, provided it has not rained.

If you see any of these signs, your garden will need to be designed as a backyard wetlands garden, or another location should be selected. Otherwise, your site is suitable for a rain garden.

How large should the rain garden be?

Rain gardens can be large or small – the size depends primarily on the site drainage area. The volume of water collected will be roughly equivalent to the amount of rain falling on impervious areas draining to the garden location, such as driveways, rooftops, and lawns (if included in the drainage area). To determine the volume of runoff to be collected, first determine the square footage of the surfaces that will provide the flow into the garden. If a gutter downspout will run directly into the garden, the only information that you will need is the area of the roof that contributes to that gutter. Measure the footprint of your house (the area taken up by your house if you were looking down from above). Then estimate how much of this area actually contributes to the gutter downspout. In other words, if it were raining, what portion of the roof area would be contributing water to the garden? Next, divide this area by 6. This calculation sizes the garden to hold one inch of roof runoff in a garden 6 inches deep. For example, suppose a house has a footprint of 60 feet x 30 feet, or 1800 ft2. One quarter of the roof area contributes to the gutter near where the rain garden is to be built. Therefore, the contributing area would be 1800 ft2 x 0.25 = 450 ft2. This area is then divided by 6, so that the square footage of the rain garden would be 450 ft2 / 6 = 75 ft2. A nicely shaped rain garden might be 10 ft x 7.5 ft. However, you have the flexibility to make it any shape you want, as long as you approximate the size. With silty soils, the size can be increased about 50%. If the soils are clayey, the size can be increased up to 100%. This increase will provide the same amount of treatment as if your soils were sandy. If you are including runoff from driveways or lawn areas, be sure to calculate the square footage and add that to the total to get the correct size needed. Once you have determined the total drainage area for your rain garden, use the following chart to determine possible rain garden dimensions. Dimensions are given for ponding depths of 6 inches and 3 inches. A good rule of thumb is that the rain garden should be about twice as long (perpendicular to the slope) as it is wide.

Drainage Area Required Size of Rain Garden
(6″ deep)
Potential Rain
Garden Dimensions
(ft x ft)
Required Size of
Rain Garden
(3″ deep)
Potential Rain Garden Dimensions
(ft x ft)
800 ft2 40 ft2 4×10, 5×8, 6×7 80 ft2 7×12, 8×10, 9×9
1000 ft2 50 ft2 5×10, 6×8 100 ft2 7×15, 10×10
1200 ft2 60 ft2 4×15, 5×12, 6×10, 8×8 120 ft2 10×12, 8×15
1400 ft2 70 ft2 5×14, 7×10 140 ft2 10×14, 7×20
1600 ft2 80 ft2 7×12, 8×10, 9×9 160 ft2 8×20, 10×16
1800 ft2 90 ft2 6×15, 7×13, 8×12, 9×10 180 ft2 9×20, 10×18, 12×15
2000 ft2 100 ft2 7×15, 10×10 200 ft2 10×20, 14×15
2500 ft2 125 ft2 8×16, 10×13 250 ft2 10×25, 13×20, 15×17
3000 ft2 150 ft2 10×15, 12×13 300 ft2 10×30, 15×20
3500 ft2 175 ft2 8×16, 10×13 350 ft2 14×25, 18×20
4000 ft2 200 ft2 9×20, 12×15 400 ft2 16×25, 20×20
5000 ft2 250 ft2 10×25, 13×20, 15×17 500 ft2 20×25

Installing the rain garden

Once you feel confident in the placement of the garden, lay out the shape to define where to dig. Outline the area of the proposed garden by spraying with non-toxic soccer-field paint. Another method is to lay a hose along the shape of the garden, then dig along the hose. This gives a nice flowing border to the garden area. Alternatively, you could simply choose a rectangle as the shape of your garden.

If the yard is fairly level, you can just dig out the bowl to the proper depth, which is 6 inches deep, or a couple of inches deeper if mulch will be used. If the yard is sloped, you may need to construct a small berm (mound) at the down-slope side of the garden to prevent the soil from washing away after a storm. Use the soil that was removed from the upslope side of the garden and add it to the down-slope side. The bottom of the garden should be fairly level to maintain the storage area inside the garden. Slope the edges of the garden, but do not make them too steep. Steep slopes tend to erode easily. Mulch or a ground cover will help to stabilize the soils.

If the selected area is lawn, you will have to remove the turf. Either you can use this in another area of your yard, or it can be composted to help improve your soils. If your soil drains well, simple soil preparation is all that is needed. Incorporate compost into the garden bed to improve the quality of the soil. If your soils are clay, soil replacement is probably in order. You may also want to add a reservoir of gravel at the bottom of the garden bed, or add tiles or an under-drain that leads to another area. This will avoid having your rain garden become waterlogged. The idea is to create a living sponge of soil, plants, roots and mulch, not a soggy bog.

Grade the surface of your prepared rain garden bed in such a way that the water entering it can spread out over a large flat area and soak into the soil. This may involve removing a lot of soil. When your ponding area is ready and the soil is nice and loose, it is time to plant. You can prepare a rain garden bed and then cover it with mulch until later; then, plant through the mulch. On the other hand, you can plant immediately, and then mulch the plants. The choice is yours. The sooner the plants are in, the faster your rain garden will become established.

Planting the rain garden

While rain gardens are a highly functional way to help protect water quality, they are also gardens and should be an attractive part of your yard and neighborhood. Think of the rain garden in the context of your home’s overall landscape design. When choosing plants for the garden, it is important to consider the height of each plant, bloom time and color, and its overall texture. Use plants that bloom at different times to create a long flowering season. Mix heights, shapes, and textures to give the garden depth and dimension. This will keep the rain garden looking interesting even when few flowers are in bloom. A small tree or a few flowering shrubs may be included in the rain garden if it is large enough. It is important to note that plants in a rain garden will have to tolerate fluctuating levels of soil wetness. Your rain garden will have a couple of different wetness zones in it. In the deepest part of the garden, you can put plants that withstand a couple of days of standing water at a time. In the shallower parts and on the edges, you can put more typical landscape plants. Drought tolerant plants can be planted on the perimeter. Many native plants make great candidates for the rain garden and are generally adapted to local growing conditions. Introduced ornamentals may also be used as long as they have no invasive characteristics or problem pests.

When laying plants out, randomly clump individual species in groups of 3 to 7 plants to provide a bolder statement of color. Make sure to repeat these individual groupings to create repetition and cohesion in a planting. This will provide a more traditional formal look to the planting.

Use container-grown plants with a well-established root system. Dig the hole for each plant twice as wide as the plant container and deep enough to keep the crown of the young plant right at the soil line, as it was in the container. After you put the plant in the ground, gently tamp the soil around the roots to eliminate air pockets. Water immediately after planting, and then water weekly, to a depth of several inches, until the plants are well established. After the first growing season, you should not need to water the plants unless there is a lengthy drought. Add mulch two inches thick, keeping it off the crowns of the plants. Use mulch that will not float away; hardwood mulch is best.

The following plants are some of those that are suitable for inclusion in a rain garden:

Trees
Name Exposure Moisture Mature size Bloom
Acer palmatum Japanese maple Sun to part shade Moist 5′-25′ depending on cultivar Not significant Graceful small tree; green or red leaves, some with deeply dissected leaves; excellent fall color
Acer rubrum
Red maple
Sun to part shade Dry to wet 40′-60′ April Shallow root system; attractive red flowers and fruit; tolerates moist or dry sites; red/yellow/orange fall color
Betula nigra River birch Sun to part shade Dry to wet 40′ Not significant Tolerates wet feet or upland site; interesting catkins; beautiful peeling bark; yellow fall color
Carpinus caroliniana American hornbeam Part sun to shade Moist 20′-30′ May Tolerates sun if soil is moist; tolerates periodic flooding; unique fluted silver-gray bark; yellow, red, or orange fall color
Cornus kousa Kousa dogwood Sun Moist to dry 25′-30′ June/July Resistant to dogwood anthracnose; large white bracts appear after the foliage; reddish purple fall color
Magnolia virginiana Sweetbay magnolia Sun to shade Wet to moist 15′-20′ June Large white fragrant flowers; small multi-stemmed tree; red berries; semi-evergreen; will tolerate wet soils
Nyssa sylvatica Tupelo Sun Wet to dry 30′-50′ Not significant Tolerates seasonal flooding or dry, rocky uplands; blue-black berries taken by birds; brilliant scarlet fall color
Shrubs
Aronia arbutifolia Red chokeberry Sun to part shade Dry to wet 4′-10′ May/June White flowers with red stamens; bright red, edible berries persist in winter; salmon to scarlet fall color
Aronia melanocarpa Black chokeberry Sun to part shade Dry to wet 3′-5′ May/June White flowers with red stamens; black berries persist in winter; dark purple-red fall color
Callicarpa americana Beautyberry Sun to part shade Moist 3′-8′ July/August July/August
Clethra alnifolia Sweet pepperbush Sun to part shade Moist to dry 6′-8′ July/August Very fragrant white or pink flowers; yellow fall color; butterfly nectar plant
Cornus stolonifera Red twig dogwood Sun to part shade Moist 6′-8′ June White flowers; blue or white berries; red/maroon fall color; scarlet twigs in winter
Hamamelis x intermedia Hybrid witchhazel Sun Moist to dry 12′-15′ December/April Winter bloomers in yellow, red or copper; in bloom for 4 to 6 weeks; many cultivars
Hamamelis virginiana Witchhazel Sun to part shade Moist to dry 12′-15′ October Tolerates irregular flooding or dry sites; yellow fragrant strap-like flowers; yellow fall color
Hydrangea arborescens Smooth hydrangea Sun to part shade Moist to dry 3′-8′ June/July Creamy white flowers on new wood; cv. Annabelle has large flower heads; cv. White Dome is a lace-cap type
Hydrangea paniculata Panicle hydrangea Sun to part shade Moist to dry 5′-12′ July/September Large panicles of white flowers turn to pink by fall; blooms on new wood; many cultivars available
Hydrangea quercifolia Oakleaf hydrangea Sun to part shade Moist to dry 5′-8′ July Pyramidal white flower heads age to mauve; large oak-shaped leaves with deep red fall color; shaggy reddish bark is attractive
Ilex glabra Inkberry Sun to part shade Wet to dry 3′-6′ Summer Slow-growing evergreen; creamy-white flowers; tolerates wet soils; need male & female for berries
Ilex verticillata Winterberry Sun to part shade Wet to moist 6′-10′ June/July White flowers; yellow fall color; need male & female for scarlet berries; tolerates wet soil
Itea virginica Sweetspire Sun to part shade Moist 4′ May/June Fragrant white flowers; fall foliage garnet to purple
Leucothoe racemosa Fetterbush Partial shade to shade Wet to moist 4′-6′ May/June White drooping flowers; evergreen leaves turn red/purple after frost
Physocarpus opulifolius Ninebark Sun Moist to dry 8′-10′ May/June Cultivars are better than the species; ‘Diablo’ has purple foliage while ‘Dart’s Gold’ has yellow foliage; drought tolerant
Rhododendron viscosum Swamp azalea Sun to part shade Wet to moist 6′-8′ July/August Intensely fragrant white flowers; bronze fall color
Sambucus canadensis Elderberry Sun to part shade Wet to moist 6′-8′ June/July Large white flower clusters; ornamental, edible purple berries; fast-growing
Sambucus nigra European elderberry Sun to part shade Moist 10′-15′ June Larger than S. canadensis; numerous cultivars with colorful foliage
Viburnum dentatum Arrowwood Sun to part shade Moist to dry 8′-10′ May/June Creamy white flowers; blue berries; crimson fall color
Viburnum sieboldii Siebold viburnum Sun to part shade Moist to dry 10′-15′ May/June Creamy white flowers are followed by bright red berries which change to black, relished by birds
Viburnum trilobum American cranberrybush Sun to part shade Moist to wet 8′-12′ May White flowers; edible red berries; yellow-purple-red fall color
Perennials
Amsonia hubrechtii Willowleaf Bluestar Full sun to partial shade Moist to dry 18″-3′ May/June Trumpet shaped light blue flowers, delicate bottlebrush leaves give this plant an attractive, shrub-like appearance; leaves turn a beautiful yellow in fall
Andropogon gerardii Big bluestem Sun Dry to moist 3′-5′ August/September Prairie grass with purple flowers; blue-green blades turn tawny in fall; tolerant of acid soil, sandy soil, flooding and drought
Aquilegia spp. Columbine Sun to part shade Moist 2′ May/June Flowers attract hummingbirds and butterflies, elegant blue-green divided foliage
Asclepias incarnata Swamp milkweed Sun Wet to moist 2′-4′ June/July Pink blooms in midsummer; butterfly nectar plant; monarch butterfly host plant
Aster divaricatus White wood aster Part shade to shade Moist to dry 1′-3′ September/October Good for dry shade or moist woods; white flowers attract butterflies; attractive massed at woodland edge
Aster laevis Smooth aster Sun Moist to dry 2′-4′ August/October Pale blue flowers attract butterflies; mildew free
Baptesia australis Blue false indigo Sun Moist to dry 3′-5′ May/June Indigo-blue showy flowers on blue-green, compound foliage make a striking show; effect is shrub-like
Chelone glabra White turtlehead Sun to part shade Wet to moist 2′-3′ September/October White snapdragon type flowers; good fall bloomer
Chelone oblique Pink turtlehead Sun to part shade Wet to moist 1′-4′ September/October Pink snapdragon type flowers
Cimicifuga racemosa Bugbane Part shade to sun Moist 5′-6′ July/September Bold woodland edge plant with white, wand-like blooms; handsome foliage
Coreopsis verticillata Tickseed Sun Dry to moist 2′-3′ June/July Yellow mini-daisies are held above delicate mound of lacey foliage; slowly spreading to form a small colony
Dennstaedtia punctilobula Hay scented fern Sun to part shade Dry to moist 1′-3′ n/a Spreads rapidly; fragrant, light-green foliage turns yellow in fall
Echinacea purpurea Coneflower Sun Moist to dry 3′ July/August Pink petals surround a bronze cone; a butterfly magnet
Eupatorium maculatum Joe Pye weed Sun Wet to dry 5′-8′ July/August Huge, dusty-pink flowers attract butterflies; good fall color
Eupatorium rugosum White Snakeroot Part shade to sun Wet to moist 3′-4′ September Long lasting, fuzzy white flower clusters; cv. Chocolate has purple/brown foliage
Filipendula rubra Queen of the prairie Sun Moist 4′-6′ June/July Prefers well-drained evenly moist soils but will tolerate wet soils; foamy clusters of tiny pink blooms.
Geranium spp. Perennial geranium Sun to part shade Moist to dry 10″-18″ May/July Many species and cultivars; colors range from white to pink to blue
Hemerocallis spp. Daylily Sun to part shade Moist to dry 2′-3′ Summer Many colors; extend season with early, mid, and late blooming cultivars; drought tolerant
Heuchera spp. Coral bells Part shade to sun Moist 1′-1.5′ May/June Pink, coral or white flowers on spikes, many cultivars with purple/silver mottled foliage
Hibiscus moscheutos Rose mallow Sun Wet to moist 3′-5′ July/September Shrub-like plant; very large pink or white flowers; hummingbird nectar plant; can grow with roots in water
Hosta spp. Hosta Part shade to sun Moist to dry 6″-3′ Summer Hosta come in many sizes and foliage colors; mostly grown for foliage, their flowers are quite attractive; remarkably drought tolerant once established
Iris siberica Siberian iris Sun Moist to dry 3′-4′ May/June Many colors, foliage turns apricot yellow in fall
Iris versicolor Blue flag Sun Wet to moist 2′-3′ May/June Deep blue blooms on attractive grass-like foliage; can grow with roots in water
Liatris spp. Gayfeather Sun Dry to moist 2′-4′ July/August Tall stems carry purple flowers that open from the top down; foliage is grass-like; very drought tolerant
Lobelia cardinalis Cardinal flower Part shade Wet to moist 3′ August Will grow in full sun if kept moist; brilliant scarlet flowers attract hummingbirds
Lobelia siphilitica Great blue lobelia Part shade Moist 2′-3′ August/September Blue flowers remain in bloom for 3 to 4 weeks
Matteuccia pennsylvanica Ostrich fern Sun to shade Moist 4′-5′ n/a Plants form colonies by underground rhizomes; tall, gracefully arching fronds
Monarda didyma Beebalm Sun to part shade Moist 3′-4′ July/August Many cultivars available in a range of colors and mildew resistance; forms small colonies; attracts hummingbirds and butterflies
Osmunda cinnamomea Cinnamon fern Shade to sun Moist 3′-5′ n/a Interesting cinnamon colored spore fronds appear in the center of the plant; needs constant moisture if in sun
Panicum virgatum Switch grass Sun Dry to moist 3′-6′ July/September Many good cultivars available; tolerates flooding; airy seed heads in summer
Rudbeckia spp. Black eye Susan Sun Dry to moist 2′-5′ June/September Many different species offer color through the season; both annual and perennial
Schizachyrium scoparium Little Bluestem Sun Dry to moist 3′-4′ August Lovely native grass, blooms in August and turns buff/golden in fall; dense root system; tolerant of poor soils
Solidago spp. Goldenrod Sun Dry to moist 18″ – 4′ July/October Many species available; does not cause hay fever; great late season color
Tiarella cordifolia Foam flower Part shade to sun Moist 1′ May Spikes of foamy white flowers in spring; forms a small colony
Groundcovers
Ceratostigma plumbaginoides Leadwort Sun to shade Moist to dry < 1′ August/September Shrubby groundcover spreads rapidly in loose soil; drought tolerant; brilliant blue flowers; leaves red in fall and spring
Chrysogonum virginianum Green and Gold Partial shade Moist to dry < 1′ May/June Golden daisy-like flowers continue sporadically until frost; spreads easily
Epimedium grandiflorum Bishop’s Hat Partial shade to shade Moist to dry 1′ May/June Foliage remains green most of the year, once established it will tolerate dry conditions
Phlox subulata Moss Phlox Sun to part shade Moist to dry < 1′ April/May Evergreen; flower colors range from blue to pink and white; forms mats

Maintaining the rain garden

Just like any other garden, your rain garden will need some basic maintenance to keep it healthy and functioning.

  • Mulch annually to suppress weeds and to keep soils moist, which allows for easy infiltration of stormwater; un-mulched surfaces may develop into a hardpan, which impedes water infiltration. Before applying new mulch, remove the old mulch. Alternately, loosen up the old mulch with a rake and just top dress it with new mulch. The depth of the mulch should never exceed 3″.
  • Weed your garden, especially during plant establishment; newly planted species may have a tough time competing with weeds. Once plants become established, less weeding will be required.
  • The plants in your rain garden will need to be watered regularly during establishment to ensure healthy growth. Once established, plants should be watered in long periods of drought. Water deeply once or twice a week; avoid frequent shallow watering.
  • Keep your garden healthy and clean. Rain gardens should be periodically cleared of dead vegetation and any debris that may collect. Replanting may be necessary over time. If a plant is not doing so well in one location of the garden, it may have to be moved to a wetter or dryer area.

Enjoy your rain garden and your contribution to water quality in your neighborhood.

Written by: Roberta Clark
Revised: 08/2011

Adapted from:

  • How Does Your Garden Grow: A Reference Guide to Enhancing Your Rain Garden.
    LID Manual, Prince Georges County, MD, Dept. of Environmental Resources
  • Rain Gardens: A Household Way to Improve Water Quality in Your Community.
    University of Wisconsin Extension and Wisconsin Department of Natural Resources
  • Rain Gardens: A How-to Manual for Homeowners.
    University of Wisconsin Extension and Wisconsin Department of Natural Resources
  • Backyard Rain Gardens.
    North Carolina Cooperative Extension

Many practices exist for managing rainwater runoff on your property. Called Low Impact Development (LID), these practices help control and minimize runoff leaving your property. For ideas on how to manage your runoff, this site will periodically post different practices.

Rain Gardens

What is a Rain Garden? Understand what a rain garden is an how it helps beautify your yard and protect the environment. (Slide show with audio).

A rain garden is a planter bed 6 to 12 inches deep into which rain from your downspouts is directed, usually a site at least 10 feet from your foundation and slightly downhill from your downspout.

Site suitability is important! If a one foot deep hole filled with water drains within 24 hours, it is suitable for a rain garden. The rain garden is a depression about one foot deep and sized to be approximately one tenth the size of the roof area drained by your downspouts. Adding 4 to 6 inches of good compost provides a good planting medium. Downspouts can be directed to the rain garden by creating a dry rock streambed or burying a pipe to the garden.

Rain gardens can be planted with a variety of shrubs and perennials similar to a garden bed. Virtually any plant that does not require well drained soil will work. Native plants work best as they are less susceptible to disease and drought. Integrating the design of the rain garden into the rest of your landscaping provides the most pleasing results. Rain gardens are often focal points in the landscape.

Rain Garden Handbook for Western Washington Homeowners. A downloadable resource from WSU Extension covering rain gardens from design to digging to maintenance.

Rain-Friendly Landscaping Project

Introduction

Have you ever had the unfortunate experience of seeing your driveway flood in the wet months? Or maybe you’ve had some plants that drowned in the winter rains, but just don’t have enough water in the summer? Do you have tons of overgrown blackberries and ivy in your yard? If any of these issues sound familiar, this information may be of use to you.

Image from Clark County Washington

What’s stormwater? Where does it go and why is it important?

The image to the right shows the major watersheds of Clark County. All rain falls into some watershed, which is the area of land where all groundwater and rainwater falling within its boundaries drains into the same place (More at What is a Watershed?). In the Pacific Northwest, most water once fell directly onto the ground and soaked into the soil. However, we’ve altered the landscape with buildings and other construction, changing where the water ends up.

Stormwater runs off impervious surfaces, such as roofs, driveways, and sidewalks. As the water flows over these surfaces it collects a number of pollutants, including motor oil, pet waste, grass clippings, dirt, and litter. In the more urban areas of Clark County, the water goes into stormwater drains which lead into streams and eventually to the Columbia River. This can harm wildlife and people alike. You can look at the health of different watersheds in Clark County at Clark County, Washington’ Stream health and monitoring pages.

What can we do about this? In a nutshell, we can help the land do its job to filter out pollutants from our water, instead of directing all of the stormwater to streams and other waterbodies. One way to do this, called low impact development (LID), directs the flow of water back into the ground. LID practices include rain gardens (image below), pervious pavement, using drought-tolerant plants (especially native plants), and planting the “right plant for the right place”.

A rain garden at the Pacific Park Natural Garden Demonstration Site in Vancouver, WA.

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