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Maintaining Rain Gardens through the Changing Seasons

Early on an unseasonably hot September morning, Master Water Stewards from south Minneapolis were hard at work, weeding a massive rain garden that runs alongside Highway 55. While the steamy weather might’ve suggested otherwise, these seasoned Minnesotans realize that winter is on its way. Before the snow falls, there’s work to be done prepping rain gardens for winter.

Roxanne Stuhr is the mastermind behind this rain garden. A lifelong gardener, she established a garden maintenance company when she was just 17 years old that financed her college education. Six years ago she established her own landscape design company called GreenSpace: True Nature Design, and in 2015 she was certified as a Master Water Steward.

Rain gardens keep pollution out of lakes and streams

Roxanne is committed to keeping our shared waterways clean through responsible, holistic design. Rain gardens, designed to capture and hold runoff from impervious surfaces like parking lots and roofs and allow moisture to soak into the ground, are an important part of her design philosophy. “I’m a huge proponent of keeping water on our properties,” she says, “The key is to design it properly and to be realistic.”

All too often stormwater carries litter from the gutter into storm drains, eventually flowing into nearby Lake Hiawatha and the Mississippi River. This rain garden will protect lakes and rivers by filtering water from the warehouse roof into the soil. It gently slopes alongside Reddy Rent’s large warehouse building that fills nearly an entire block near Highway 55 in south Minneapolis. The garden is thriving with Black-Eyed Susans and Echinacea that lean out into the sidewalk and buzz with pollinators.

Hidden out of sight, French drains located under the roof’s downspouts capture the enormous amount of rainwater that streams off the warehouse building. French drains are trenches dug into the garden and filled with gravel or reservoir cubes to move rainwater deeper into the soil. The native plants in the garden have root systems that extend up to 30 feet underground. Thanks to Roxanne’s careful design, the rain garden holds water for 24 hours after a storm, giving the plants’ deep root systems sufficient time to absorb runoff.

Maintenance is key to garden success

Though native plants do not need to be pampered, all gardens need upkeep. Take it from Roxanne: “Everything in life requires maintenance, including our gardens.” She recommends that home gardeners weed every other week when establishing a new garden, with extra vigilance during the months of May, June and September.

Even when your garden is established, proper weeding is key. In only three years of neglect, the root systems of weeds and your garden’s desirable plants can become so entangled that they’re impossible to separate.

“It’s a common misconception that when a garden is full of plants no maintenance is needed,” says Roxanne. She recommends home gardeners make use of the University of Minnesota’s Weed Identification site to recognize the weeds in your rain garden.

Autumn Tips for Your Rain Garden

Follow Roxanne’s simple tips to prep your rain garden for winter.

Clean Up!

• If your rain garden design includes a dry creek bed or another drainage depression, use a blower to remove debris.
• Weed out undesirable plants with help from the U of MN Weed Identification site.
• Check the depth of your rain garden. A rain garden that is too deep will hold water for too long or present a tripping hazard. If it’s not deep enough, it won’t absorb runoff because the water will flow right out. Remove any excess mulch or roof sediment that has built up around plants. (Click here for more information about determining your rain garden’s optimal depth.)

Mulch if needed

• Mulching will protect your plants from a temperature differential, which is particularly important for trees and shrubs.
• Take care to mulch properly with 1-2” depth around perennials and 3-4” around trees and shrubs.
• Make a “donut” around trees and shrubs. Do not pile mulch up in a “volcano” around trunks.

Divide and move plants if they’re overcrowded

• Click here for common signs that it’s time to divide a plant.
• Dividing in excess heat or cold will stress plants. Aim for 45-65 degrees for success.
• Share extra plants with your neighbors.

Save the seeds

• Don’t cut back native plants until spring. Their seeds are a great source of food and for winter wildlife. Plus they look lovely poking out of winter snow cover.

* You can find more information about rain gardens, native plants, and gardening for clean water at Blue-thumb.org.

* The Master Water Stewards program, created by the Freshwater Society, certifies and supports community leaders to install pollution prevention projects that educate community members, reduce pollutants from stormwater runoff, and allow more water to soak into the ground before running into storm sewer systems. More information is available here: https://masterwaterstewards.org/

*Download Roxanne’s maintenance tips as a PDF for future reference.

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