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Rain Garden Design

How to design environmentally friendly, water-efficient gardens using natural rainfall.

Rain Garden PlantsRain gardens catch and channel the environment’s natural precipitation, delivering it where it will most benefit our plants. At the same time they protect the environment by keeping polluted runoff out of municipal storm sewers. They allow water to percolate into the soil where its needed, avoiding erosion. A well-designed rain garden is sustainable, requiring little or no additional water to maintain life.

Unlike active rainwater harvesting, where runoff from roofs, pavement, and other impermeable surfaces is collected and stored in barrels and cisterns, passive rainwater collection takes moisture when it falls and puts it to best use. But its water may also be collected from those impermeable surfaces, like driveways, and .

Water is the key to life, and plants need it as much as people do. When Mother Nature doesn’t deliver, you and your crop don’t have to suffer. We’ve got backup watering equipment, garden hoses and specialized nozzles for automatic or precise irrigation. Plus rain barrels, which save precious water that would just roll through your gutters.

The most common and simplest rain garden feature is the shallow trough designed to catch and hold water encircling a tree. Complex garden designs that deal with difficult environmental conditions may involve earth-moving and soil replacement as well as underground piping systems to conduct excess amounts of water.

Often mimicking natural terrain in their layout, rain gardens also require attention to soil drainage. Soil itself often serves as a reservoir for collected rainfall.

Native plants that have evolved to survive a specific area’s weather patterns are best at utilizing natural moisture patterns. But a rain garden can also sustain non-native, moisture-loving plants along its ponds, channels, and other water retaining features.

Rain gardens can be small areas built to catch rainwater and runoff in a corner of a yard. Or they can swallow your whole landscape, front and back.

Driveways of spaced pavers, planted with moss, grasses, or other ground-hugging plants in the gaps that allows runoff to seep into soil rather than straight to the street, are one of the many various kinds of rain garden. Depending on their location, rain gardens can be designed to host cacti and succulents or produce fruits, vegetables and berries.

Rain gardens are also used to prevent flooding. These (PDF) can include bottom or overflow drainage of holding ponds. Underground, perforated pipes are used to conduct water away from collection points and channel it downstream to storm sewer connections.

Professional landscape architects and landscapers can be hired to design and build your rain garden. You might want to consider utilizing them for large, involved projects. But most home gardeners are capable of designing small, contained gardens and then adding to them as their experience mounts.

Four components to consider when designing a rain garden, each affecting the other:

Terrain

Is the area flat? Are there natural depressions or water courses? Where do you want the water to collect, where do you want it to go? Consider the slope of the site and if steep, consider (PDF).

Precipitation Patterns

What amount of precipitation should you expect and when can you expect it? Does it come in the form of winter snow, does it come all at once in thunderstorms or monsoon down pours? When are the dry seasons, how long will your spring and winter moisture last between showers? Daily attention to moisture patterns, including the number of overcast days, coastal fogs, high and low temperatures, humidity, and precipitation amounts, will help you make the right choices about what type of water retention features and plants are best for your particular micro-climate. Don’t rely on generalized weather records supplied by distant third party interests. Keep your own weather observations as part of your garden journal.

Made in the USA with 100% recycled materials! The Rain Wizard 5o gallon rain barrel captures runoff from your roof and stores it for a not-so rainy day. When your garden needs the extra moisture, just hook a hose to the brass spigot.

Earth and Soil

In a rain garden, the ground often serves as the reservoir for gathered water. Clay soil resists water retention and will need improving with sphagnum peat moss or other soil builders with plenty of organic material. No matter the quality of your soil, regular additions of compost will help it retain moisture.

Certain surfaces, like the bottom of holding ponds and water channels, will use materials that hold water or control its percolation into the ground. Stoned-lined watercourses with water conducting earth beneath them or gravel-bottomed pools atop water-retaining soil are also part of a rain garden’s surface.

Plants

The overall climate conditions your rain garden plants will face generally guide their choosing. But also consider the different conditions and micro-climates in your own landscape.

Choose plants best adapted to the moisture conditions you’re expecting in various parts of your garden. Deep or thick rooted plants on slopes helps control erosion and prevents above-ground runoff. Trees and shrubs that need less moisture are best suited to high ground, those requiring more are best at low points or near water-holding features.

Most environments require plants adapted to alternating wet and dry seasons. Many require plants to overwinter. Choose carefully in accordance with your local growing conditions. Favor native grasses and flowering plants.

Choose plants with an eye to aesthetics. Consider color, shape, dimensions, and seasonal differences of plants before placing them in the garden. Resist trying to grow a particularly attractive tree, shrub, or perennial flower where it will face a challenge to survive. Instead, look for something close but more suited to the conditions, even if it’s not as pretty. Making it easy for your plants makes it easy for you.

Tips & Techniques

  • Use raised berms around the perimeter of small rain gardens or water-collecting features in larger gardens to contain runoff and allow water to soak into the ground. Berms around trees help keep rain from draining away from where it will do the most good.
  • Soil depth for good water retention and root growth should be at least 12 inches and as much as two feet for some plants. Trees will need their own hole to the depth recommended by your nursery person.
  • A three inch or deeper layer of gravel laid first beneath your soil will help conduct away excessive water in wetter climates.
  • If possible, place the rain garden where it will receive runoff from driveways, sidewalks, and patios. Siphon rainwater from your home’s gutter into downspouts that empty into water features.
  • Plan a mix of plantings that will allow sunlight into your rain garden. Large trees tend to create large, shaded areas where it’s difficult to grow other things.
  • Keep plantings at least six feet from the walls of your home to prevent seepage and foundation damage.
  • Avoid putting rainwater features over septic systems. Inquire about the position of underground utilities in your yard before any extensive digging.
  • Consider the effects of plantings on your home and surrounding environment. Shade the south side of your home with trees or shrubs in warm, sunny climates, planted at a safe distance.
  • Don’t be afraid to use additional waterings when first establishing plants in your rain gardens. Help your plants establish the deep healthy root systems that will ensure strong growth.
  • Some local and state government agencies offer to those installing rain gardens. Check with your municipal offices or county extension representatives.

Here’s a long, (PDF) from the Wisconsin Department of Natural Resources and University of Wisconsin Cooperative Extension service on designing and building home rain gardens. And here’s (PDF) on designing and building features to control yard and driveway runoff.

Rainwater is a valuable resource. Let’s treat it that way.

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