DIY rain garden – The New York Times

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When it’s raining all weekend and you’re stuck at home, you have time to notice a lot of things. For example, in a place where water drains off the roof too quickly, and part of the water disobediently sneaks into the basement. Or maybe you’ve watched rainwater pour down your driveway, right into a storm sewer, or into a depression in your lawn where it always seems to drain after a rainstorm.

A scaled-down version of stormwater management tactics used in municipal planning can help solve these problems by slowing down the flow of water and increasing infiltration. And if the solution is landscape-oriented and involves planting native species, it will also support pollinators and other beneficial insects, contributing to overall diversity.

Think of it as your own rain garden that comes to your rescue – and a little more.


At her home near Wilmington, Delaware, Carrie Wiles develops a plan to redirect water that flows from the roof above her kitchen and dining room into the basement during new normal rainfalls that follow extended periods of drought. Ms Wiles, Grower and Marketing Manager at North Creek Nurseryfrom Landenberg, Pennsylvania, is familiar with the idea of ​​using plants to solve environmental problems.

North Creek, whose motto is “Where Gardening Meets Ecology,” is a wholesaler of so-called plugs or inserts, many of which are species native to the eastern United States. These seedlings are sold not only to garden centers but also to landscape designers, park systems, universities and municipalities. The company specializes in plants used to restore forest habitats and create grasslands, as well as those that solve water problems in smarter ways.

Ms. Wiles knows that lengthening the bottom end of the downspout or adding a longer splash is not enough to solve her problem. She also knows that the lawn behind the drainpipe won’t help much. Compared to properly selected native plants with a much deeper root system, the lawn is a poor substitute where water management is needed, she said. This is another of many reasons to reduce the amount of cut grass.

First and perhaps most importantly, the rain garden is not a water garden, although the main part of it is in the form of a pool or shallow pond.

“It is designed to trap and retain this water for a short, specified period of time – maybe 12 or 24 hours – as it penetrates or seeps into the ground,” said Ms. Wiles.

In his book Sustainable Stormwater Management: A Landscape Approach to Planning and Design, Thomas W. Liptan, landscape architect, explained the main objectives of stormwater landscape management, as well as principles that are relevant regardless of whether the project is a large municipal project. or the yard is small.

“Add water to the landscape,” Mr. Liptan writes, “not in the basement, running down the driveway, or through the garden, washing out ravines where impenetrable surfaces such as roofs and sidewalks lined his path.

In his opinion, you can help the water move through the landscape by creating a functional and attractive design. In some areas, this may mean a straight bed; elsewhere it may be something curvilinear. The garden also needs to be planned with follow-up care in order to facilitate maintenance.

A rain garden has three main components.

The main feature is a shallow pool, usually about six inches deep, which is large enough to contain the drain you are trying to handle. If you plan on mulching around perennials or shrubs that will be planted in the pool, dig up to eight or nine inches to account for this layer (and be sure to use shredded mulch, not shavings that will float to the surface).

To direct the water from its source to the pool entrance and slow it down a bit, Ms. Wiles recommends installing a dry stream bed of stone or coarse gravel.

And at the farthest or very bottom from the water source is the third component of the garden: a small ledge or ledge.

Where in your home landscape would a rain garden (or several) be most effective? “Plan to spend the next two showers outside to figure it out,” advised Miss Wiles, observing the water and how it naturally moves – for better or worse – according to the current settings.

“Look first of all at how water flows from the roof and down into the downpipes from the house,” she said. “Also keep an eye on where he is going to team up.”

Look again a couple of hours after the storm ended, and then 12 and 24 hours later to see how quickly it seeps into the ground. Take notes.

“Based on your observations, identify a relatively level potential location for your rain garden,” Ms. Wiles said. Areas with a slope of 12% or more will require extensive excavation to create a level basin with significant embankment on the far side.

Spots where bedrock is close to the surface or areas with seasonally high groundwater levels will also not work. Also, nowhere will there be water, which currently accumulates for a long time after a storm (which indicates poor drainage). A sunny area is preferable to a shady one.

Ms Wiles cautioned that the rain garden should not be closer than 10 feet from the foundation (and better if the property allows it). Also, it should not be near a septic system (make sure it is at least 15 feet away) or a drinking well (leave a distance of at least 25 feet).

Other underground realities to consider: Since digging will be required, call utilities for information on underground lines to confirm that the location you are considering is safe.

Once a suitable site has been identified, the next requirement is a baseline seepage test to assess drainage. Dig a roughly cylindrical hole about a foot deep and six inches wide. A pit digger is ideal for this task. Fill the hole with water and let it drain completely, which can take several hours. Measure the depth of the pit, then fill it with water and re-check the water depth every hour for the next four hours to calculate the infiltration rate. According to Ms. Wiles, an inch or an inch and a half per hour is ideal; Less than half an inch will not work without some soil adjustment.

The rain garden should be adequate for the potential runoff volume that may be required for placement. Most backyard rain gardens are 100 to 300 square feet; some houses have several problem areas, and several are needed.

“In a typical home, there are two main impervious surfaces that drainage occurs: the roof and the driveway,” Ms. Wiles said.

As you probably noticed while researching rain, most runoff starts from the roof, so the mathematics of rain garden size starts with that too.

Ms. Wiles uses a one-inch rainfall scenario to begin her calculations, since 90 percent of the rainfall in her area in any 24-hour period is an inch or less. Other parts of the equation are the square meters of the portion of the roof feeding the problem area, the number of downspouts serving that portion of the roof, and the soil type and slope.

Each region has its own rainfall patterns and soil types vary widely, so Ms. Wiles recommends that you search the Internet for your state or region and search for the term “rain garden size calculation” for local advice from the cooperative expansion, State Department of the Environment or another such organization. The one she used: The Three Rivers Alliance. calculator

Following the environmental philosophy of North Creek, Ms. Wiles thinks of the rain garden she plans at home as a miniature habitat with separate zones. She visualizes every zone – pool bottom, sides, top – as the most suitable for plants from a variety of habitats in nature, from wet foot tolerant species to mountainous ones.

“At the very bottom of the pool are the ones that can handle the most water,” she said, citing examples such as common reeds (Juncus effusus), upright sedge (Carex stricta), white turtle (Chelone glabra) and golden rosewort ( Packera aurea).

BUT search tool on the North Creek website allows users to filter suitable plants, including obligate wetland species (which are almost always found in wetlands) and optional wetland plants (found in wetlands and non-aquatic – wetlands). You can also highlight options with other relevant qualities, both functional and aesthetic.

According to Ms. Wiles, the plants along the perimeter of the rain garden “have to withstand real dryness between storms.”

High garden phlox (Phlox paniculata) and echinacea (echinacea) are possible. For late season coloring, it can work with algae such as Vernonia lettermannii Iron Butterfly.

And for the intermediate zone? Blue lobelia (Lobelia siphilitica) and docile plant (Physostegia virginiana) are among the top contenders.

Like others, she looks forward to seeing these plants during a downpour, knowing that they are not only beautiful but also hard at work.


Margaret Roach is a website and podcast creator. Gardening method, and a book of the same name.

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