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Spring maintenance for raingardens

The sound of birds chirping and green grass returning means that spring is here! With the warming of the season comes the need for annual maintenance for raingardens.

Raingardens capture storm water runoff from roofs, driveways and sidewalks. Raingardens allow that storm water runoff to infiltrate into the ground instead of eroding the landscape and picking up pollutants before rushing into local water bodies. These unique gardens are planted with native plants, which are hardy to Minnesota, and have long roots that create channels for storm water to seep deep into the ground while also providing beauty and pollinator habitat throughout the growing seasons.

Raingardens are a great way to do improve your local water quality, but like any garden, there is some maintenance involved. Here are a few maintenance reminders to keep your raingarden looking good and functioning to its full capacity for years to come.

Spring pruning

Each spring it is important to prune dead vegetation and plants from the previous year. Pruning should always be done in the late spring; leaving the previous year's excess vegetation in the garden throughout the winter provides several benefits for a raingarden. The excess plant material provides soil stability and reduces erosion caused by melting and moving snow. Additionally, leftover leaves and plant stems make the perfect nests for valuable pollinators that hatch in late spring.

Pollinator experts have recorded stem-nesting bees emerging as late as mid-June. If you want to clear out your gardens before then, examine broken stems for activity by bees and leave those in the gardens. Bees will plug the end of broken stems with mug or vegetation.

You can also remove dead vegetation and stems from the garden and place them in a cover of your yard. Leave them there for the summer so the bees can still emerge from the stems. For more information on stem-nesting pollinators and the best way to maintain a pollinator-friendly raingarden, visit the University of Minnesota Extension website.

When it does come time to prune, cut dead vegetation a few inches above the soil and prune perennial plants that are getting too large of unruly. Be mindful to only cut up to one-third of a perennial plants total mass. Cutting more can cause excess stress on the plant. Dead plant material can be composted or disposed of with other yard waste, but should not be combined with standard trash.

When pruning vegetation, it's a good time to also remove excess sediment and debris like leaves, trash, and sediment that has built up anywhere within the garden. Sediment should be cleared as it accumulates as it can clog the soil mix and slow drainage at raingarden outlets.

Plant replacement

With Minnesota's harsh winters, it's expected that some plants might not pop up again in the spring. The first couple years of your raingarden, you can expect anywhere from 70-80% survival rate of your existing plants--meaning 20-30% of them will need replacement to ensure your garden functions properly.

Examine your garden and locate any thin spots where plants need replacement.

If replacements are needed, this is your chance to be creative! You can purchase replacements and additional plants that match what is already in your garden, or you can try new native species for additional color and variety. Remember: gardens should only be populated with Minnesota native flowers, and should be filled with a variety of plants that grow throughout the growing season, meaning ~30% should bloom in the spring, ~30% in the summer, and ~30% in the fall. This will ensure beauty throughout the year, and will maintain pollinator habitat and nourishment for a wide range of Minnesota species.

To help you pick out the best plants for your garden, visit for an inventory of plants available at the annual Scott SWCD plant sale every spring. Plants typically are live for pre-orders in May, and plant pickup is in June every year.

Mulching and weeding

The majority of raingarden maintenance is the weeding, which should not be a surprise to anyone who has gardened before. Luckily, double-shredded hardwood mulch works great in raingardens to suppress most of the weeds.

Mulch is essential to raingardens, and double-shredded mulch works as a solid, tough layer on top of your garden that reduces soil erosion and increases plant stability. Double-shredded mulch by nature grips to itself better then standard mulch, making it more effective and longer-lasting. Replace double-shredded mulch annually as needed to maintain freshness, color, and a solid 3-inch layer. By maintaining your mulch layer at 3 inches, you will limit weed growth significantly. Mulch also makes weeds easier to pull out when they do pop up as weeds root in the shallow mulch layer rather then dense soil.

The first few years of the raingarden require the most weeding while the native plants become established. Some weeding is necessary in future years, but the native plants will fill in the empty space where weeds tend to grow and will be large enough to shade out many small weeds. Pull weeds early in the year when spring weeds like dandelions are out, and once more in late June - July when summer weeds like crabgrass sprout.

Maintaining the edging

To ensure your raingarden continues to function as designed, keep the edge of the garden defined. You can do this with a physical boarder of rocks or plastic edging, or by diligently weeding along the edge to keep the grass from encroaching.

Taking these steps every spring will keep your raingarden functioning and beautiful for many years to come!

If you have questions about raingarden maintenance or are interested in installing a raingarden in your yard, give us a call at 952-492-5425 or via email at! Technical assistance and financial incentives may be available for help in installing raingarden.


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