What the Heck is a Vegetative Swale?
There are two different types: one is engineered; one is not.
Let’s take the non-engineered one first:
It is simply a drainage ditch that is filled with dense and/or deep-rooted, water-loving native plants that will infiltrate rainwater instead of allowing it to move as fast as possible off the property to be dealt with by someone else.
Here are some examples:
This is the first vegetated swale I ever saw, many years ago, in the far west area of Batavia, designed by Kerry Leigh. Blazing Star (Liatris pycnostachya) and Yellow Coneflower (Ratibida pinatta) are in full bloom in July. The real workhorses of a vegetated swale are, however, the sedges. Sedges have dense root systems that hold water like a sponge; 1/3 of the roots die every year, providing channels that rain can infiltrate, drawing it deep into the soil. I don’t know which sedges have been used here, but Common Fox Sedge (Carex stipata), Brown Fox Sedge (C. vulpinoidea), and Narrow-leaved Cattail Sedge (C. squarrosa) are commonly used.
This vegetated swale is in the far west area of Elgin. Blue Flag (Iris virginica var. shrevrei) is in bloom in June. Sneezeweed, Ironweed, New England Aster, Swamp Milkweed, Queen of the Prairie, and Sweet Black-eyed Susan will bloom throughout the season. Sedges, especially Carex scoparia, are prolific.
Two downspouts emptied at the corner of this house and cut a narrow gully downhill through the lawn to the woods at the back of the house. I filled it with moisture-loving plants. Shown above are Cup Plant (Silphium perfoliatum) and Spotted Joe Pye Weed (Eupatorium maculatum).
An engineered swale on a parkway requires digging the soil out of the drainage area so the swale is a foot lower than the surrounding ground with inlets or curb cuts that let in the rainwater that falls on the street. In addition. the soil is dug out to a depth of 4’ and a plastic perforated pipe is installed at the bottom. The soil is replaced with an engineered mix of 70% course sand and 30% compost. These are simplified and condensed directions that I have taken from the blueprints of Trotter and Associates, the engineering firm that designed the vegetated swales for my neighborhood. I make no claims to engineering expertise.
The first swale was planted by our neighborhood group and other interested citizens from our town in the SWAN (South West Area Neighbors) neighborhood in September 2012.
September 2013 Cardinal Flower (Lobelia cardinalis) and Black-eyed Susan (Rudbeckia speciosa var. sullivantii) in bloom. 1 block from my house.
More Black-eyed Susan, September 2013. Good view of curb cut.
Vegetated swale installed in the center of Spartan Drive, the entrance road to Elgin Community College campus. Blazing Star (Liatris pychnostachya) and Little Blue Stem (Schizachyrium scoparium) are apparent. Moisture-loving plants grow in the deeper center of the trench, while plants that require drier soils grow around the higher edge
Blazing Star is a stunning presence in the landscape in fall and winter in the vegetated swale at ECC.
Stiff Goldenrod and Little Bluestem in vegetated swale at ECC in September.
Northern Kane County Wild Ones will be visiting these vegetated swales at ECC and in the SWAN neighborhood on Saturday, September 28 beginning at 10:00 AM at the ECC parking lot on the corner of Spartan and Lehr Drive. You do not have to be a member to attend.