By Terry Twigg
(June 1, 2025) — When it comes to the weather, there’s no such thing as averages. Most of the winter was spent in a drought, as evidenced by too many dead or dying evergreens. In the past few weeks, though, Mother Nature seems to be trying to make up the difference, with one rainy day following another. Homeowners who watched with dismay as expensive plantings withered and died are now faced with soggy or flooded areas.
We can’t magically induce rain during periods of drought, but we can do something about excessive water on the landscape: create a rain garden!
If you haven’t heard the term before, a rain garden is simply a more or less bowl-shaped depression, sited and planted to catch excessive rainwater and hold it long enough to allow it to slowly drain into the soil, instead of running over the ground and into trouble. It’s an unfortunate fact that the more square feet of ground surface are built on or paved over, the lower the quality of drinking water in the area. That’s because the rain picks up contaminants from rooftops, roads, and driveways, and carries them in swiftly-moving currents toward waterways. Your rain garden will help counteract this problem by capturing and slowing down the rain as it falls.
As the water slowly soaks in to the soil, the ground has time to filter out the contaminants that otherwise might reach watercourses. As a bonus, erosion will be limited. It should take 24 to 48 hours for your rain garden to drain after a big storm.
Ideally your garden will be placed in a naturally low-lying spot, but always at least ten feet from the house and fifty feet from any septic system. Steep slopes are not suitable, but shallower slopes can be compensated for by using the scooped-out soil to build a berm on the low side.
The size and depth of your rain garden will depend on the size of the area draining into it and the porosity of your soil. With decent drainage, the depth need be only about 18 inches, but more clay-like soil may need to be dug down to 30 inches. Ideally, the square footage should be 20-30% of the area from which the rain garden receives water. If you can’t go that big, dig a bit deeper, or construct a second garden “downstream” from the first to catch overflow.
Rainwater may be directed toward the rain garden naturally, down existing slopes, or you may need to give it some help, creating rock-lined “stream beds” or even laying pipes from downspouts to the garden. You’ll want to bury the pipes underground so they don’t create trip hazards or get damaged by mowers.
When the digging is done, the planting begins. Take your cues from what you see growing along streams or in swampy areas. For the lowest part of the excavation, choose plants most tolerant of wet feet. Perhaps some marsh marigold—does the name give you a hint? Swamp milkweed, blue flag iris (but not its invasive cousin, the yellow variety), Joe Pye Weed, and cardinal flower are all well suited to a wet site, and will provide lots of summer color.
All four coexist happily on the banks of my pond, in soil that’s muddy most of the time, and outright under water at least once or twice a year, if the overflow pipe gets clogged and I don’t notice until the water level rises a foot higher than it should be. Halfway up the sides, still moist but not constantly wet, bee balm, coneflowers, golden alexander, and asters will thrive. When you want to add shrubs, red twig dogwood and winterberry are natural choices for the conditions found in a rain garden. They’ll take up lots of groundwater and grow quickly. As a bonus, they’ll provide lots of bright red color through the winter, plus berries for your birds.
Mulch your new plantings to suppress weed growth, and remove any invasives if they appear. Even though it’s a rain garden, you may need to water occasionally during the first year, if there’s an extended dry spell—and there probably will be. By next year, your plants should be fully established, taming the rainfall while simultaneously adding cheerful color to your yard. Time to start digging, anyone?
