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Hardscaping 101: Rain Gardens

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Hardscaping 101: Rain Gardens

September 10, 2019

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?

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.
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?

Photograph via Ramsey-Washington Metro Watershed District.
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?

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
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?

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).
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:

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