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Monday - November 30, 2009

From: Aurora, IL
Region: Midwest
Topic: Rain Gardens
Title: Plants for Bioswale in Illinois
Answered by: Anne Bossart

QUESTION:

I have a 300ft by 15 ft bioswale in Aurora, Illinois. What plants would be best used? Is there a percentage of each plant to take into consideration?

ANSWER:

What a great project! A bioswale or rain garden is the ideal marriage of function and form. It will slow down storm water runoff to allow infiltration of water into the soil. This prevents erosion, facilitates the removal of pollutants by soil biota and reduces irrigation requirements to adjacent garden areas. On top of these not insignicant benefits, the choice of appropriate native plants will also provide wildlife habitat. Because of your location not far from Lake Michigan, you will find the website Rain Gardens of West Michigan very helpful.

Your area is long and narrow so you will likely be planting a garden that will simulate a stream and bank. The light conditions will impact whether you are creating a "woodland" or "sunny meadow" stream and control your plant choices. You have an area that is large enough to incorporate trees and shrubs as well as perennials and grasses. Plant percentages are entirely up to you; you will design this garden the same way you design any other "mixed border" in your garden.

Although your swale will look like a stream and will some times have an (over)abundance of water in it, your plants will also need to be adapted to dry conditions as well. Fortunately, many plants that can survive in saturated conditions are also able to handle dry and even compacted soil. If it is possible to amend the soil before you begin to remediate compaction, you will have more success as the water will infiltrate the soil quicker. You need to evaluate your conditions before you select plants to determine how long you actually have standing water. If the water stands for an extended period, you will want to choose only plants that can tolerate those conditions.

Ultimately, your plant selection will be limited by what is available in your area but our Native Plant Database will be a great starting point. By doing a Combination Search choosing Illinois and Wet Conditions along with your light requirements and plant types, you will find many plants to choose from. You can narrow your choices even further, if you start by clicking on Recommended Species for Illinois and narrowing the search according to conditions. This will result in a much smaller list of plants that are readily available. There is also a list of recommended suppliers linked to that page.

Here are some choices from that list:

Grasses

Calamagrostis canadensis (bluejoint)

Carex stipata (owlfruit sedge)

Spartina pectinata (prairie cordgrass)

Perennials

Asclepias incarnata (swamp milkweed)

Athyrium filix-femina (common ladyfern)

Chelone glabra (white turtlehead)

Gentiana andrewsii (closed bottle gentian)

Iris virginica (Virginia iris)

Shrubs