Summer is here; school is almost over for the year, and everyone is looking forward to enjoying our tributaries and grand Chesapeake Bay. As gardeners can we do more to protect our waterways from contamination? Consider our region’s rainfall, which averages about 42–47” per year. Perhaps, we can do something more in our gardens to utilize that rainfall and help maintain clean waterways.
Let me suggest adding a small, attractive rain run-off catchment, a Rain Garden to your landscaping this summer. According to the Chesapeake Bay Foundation, in urban and suburban areas, “Rain gardens filter up to 93 percent of the oil in urban and suburban runoff…also filtering up to 90 percent of toxic metals, 70 percent of the sediment, 30 percent of the phosphorous, and at least 25 percent of the nitrogen pollution” carried in the rain that is not absorbed into the earth naturally.
In addition to being a boon to our waterways, a rain garden is a favorite hangout for birds and pollinators. Once you’ve gotten through the construction stage, a rain garden is attractive and easy to maintain.
Let me review the (1) benefits, (2) design and construction, and (3) maintenance of a rain garden.
Benefits
In addition to the “big picture”—protecting our water from runoff pollution, there are additional benefits closer to home. Rain gardens:
- Improve the neighborhood’s drainage, reducing the danger of basement or sewer backups and flooding
- Improve your property value
- Increase the aquafers groundwater flow, improving the quality of the groundwater
- Improve the landscape, particularly if you’re trying to cut back on lawn maintenance
- Create a natural wildlife habitat
- Optimize the use of available water during droughts
Design and construction
There are some simple do-it-yourself ideas, but you may want to consult a hardscape or landscape specialist before digging an indentation in your lawn.
- Simple raised planters and water barrels at downspouts are two easy ways to reduce runoff
- Rain gardens should be situated at least 10’ from building foundations and 50’ from a septic system, if you have one
- Determine the percolation rate of the area by determining how long it takes groundwater to move through the soil. (You can find directions for simple tests on-line, or have the test done by the professional.)
- Based in part on the rate at which water is absorbed, decide on the size and shape of the indentation you’ll be making in your garden or lawn. Note: situating the rain garden on a slope will make it easier to capture the runoff water, allowing runoff to settle into the earth. There are three levels of efficiency to choose from: Simple rain garden: a depression where water will collect planted with grasses and native flowers and shrubs. Intermediate: a “Biosphere” is larger, designed to capture greater volumes of run-off water. Advanced: often called a “Settling Area” is constructed where severe urban runoff is likely to occur. It can collect debris and trash, and is designed to make periodic cleaning and clearing possible. (Such a “settling area” is usually a community or neighborhood project.)
- After choosing a shape and size, remove from the area any grass or plants. Dig a hollow that is deeper than you want finally. You will add layers of soil combined with compost and top that with mulch. So, your initial depth must allow for the layers you will place in the hollow area.
- You have two choices: You can keep the rain garden spare, with attractive rocks, a few simple grasses and perhaps a bush or two. Or you can choose to fill your rain garden with plants that will create a nature area. If you do, choose plants that are native to our region. You’ll want to select some that can tolerate standing water, at least briefly, and plants that can tolerate drought conditions. The moisture loving plants will go in the deepest area of the hollow. The drought tolerant plants will be the band around the upper rim of the garden. In our region, some of the native plant favorites are: Siberian iris, Aster, Turtlehead, Phlox Gentian, Beebalm, Sedge, and Forget-Me-Nots. Check out the recommendations on the Univ. of Maryland Extension site: extension.umd.edu/resource/introduction-rain-gardens
Maintenance
While a rain garden is fairly self-sufficient, you should plan on a few regular chores.
- Prepare to regularly water the plants during the first year. As with any flowerbed, a strong root system must be established.
- Yes, even in a rain garden, someone will have to weed and trim the grasses and plants.
- Clean out the debris that will collect over time—leaves, twigs, plant detritus, silt and sand. If the rain garden is not cleaned periodically it will eventually fill in and stop working as a catchment. A garden rake may suffice, but you may need heavy-duty shovels or a gardener’s services.
A few misconceptions:
- A mosquito breeding ground: A well-constructed rain garden will absorb run-off within 24–72 hours. Mosquitoes require 4–7 days of standing water to breed
- An untidy appearance: If you want to avoid the “wild meadow” look, you can plant your rain garden with ground cover, rocks, and a decorative tree or two. You can edge, prune, and trim the rain garden to please your own aesthetics.
- A swamp in the yard: Rain gardens are generally dry, except after a heavy rain. If water remains after a few days, it may be time to clean the rain garden of built-up silt and detritus.
We live in a particularly beautiful and vulnerable region along inviting waterways. They are vulnerable to human pollutants. Adding a rain garden will benefit you and the earth.
