By Diane DeWitte
U of MN Extension Educator-Blue Earth County
---- — As you travel on Victory Drive between Madison Avenue and Main Street, it’s easy to drive right past an important fixture of water purification.
That lush, dense thicket of plants and wildflowers might look like the spot the lawn mower missed — but in reality, it’s a natural water filter that is celebrating its 10th anniversary.
Known officially as the Victory Drive Rain Garden, this copse of native plants was carefully planned and planted 10 years ago as a demonstration of the positive effects of plant filtration of rainwater.
In 2003, the Minnesota River Valley Master Gardeners applied for and received a $2,000 grant from the Minnesota Department of Natural Resources to educate local communities and install rain gardens therein. The Master Gardeners hosted a seminar for nearby community leaders to encourage the establishment of rain gardens.
The City of Mankato became their first cooperator, and in conjunction with the DNR who provided funding and great advice, the three worked together to select a site and establish the planting.
The purpose of a rain garden is to catch water coming from an impervious surface and allow it to soak into the ground before running into storm drains. Storm drains are constructed to remove excess water and discharge it directly to rivers or lakes. Research has shown that a rain garden will absorb 30 percent more water than an unimproved lawn. The rain gardens proposed through the DNR stipulated that deep-rooted native plants and grasses should populate the site.
Once the plan was in place, Master Gardener volunteers and DNR personnel selected the site on Victory Drive at the entrance of a storm water culvert. A mixture of grasses, sedges and perennial flowers was planted by the volunteers. Because a rain garden takes two to three seasons to get established, the group members each adopted different species and spent time weeding, watering and caring for the new plants.
The wide ditch site was chosen because of its proximity to a large culvert which delivers storm water directly to the river. Water coming from nearby parking lots and pavement soaks into the garden area where any fuels, debris, fertilizers or pesticides are filtered out. This natural filtration ensures that water entering the culvert is much purer than it was when it came off the pavement.
In the first two springs after establishment, volunteers cut down the wintered vegetation by hand, but soon found they needed help. In the ensuing years, the Mankato Department of Public Safety has (thankfully) assisted by burning off the dense blanket of vegetation early in the spring to allow fresh new growth.
The grasses in the Garden were slow to establish; but in their third season, they were there for good. Different species of plants and grasses have thrived. Big bluestem grass grows to 6 feet tall with seed heads waving in the wind. It is left standing all winter and provides cover and winter interest until it is removed in spring.
False indigo (baptisia) blooms in spring and early summer, and monarda (bee balm) provides summer-long flower color. Marsh-type plants which thrive in a wet or low area were also planted in the rain garden. Swamp milkweed, New England aster, iris versicolor, and prairie dropseed are other garden inhabitants who have thrived in their first decade in place.
Volunteers also found that some plantings weren’t suited for the rain garden. Rudbeckia and marsh marigold didn’t survive in the Victory Drive site. Garden caretakers have found that many of the original plantings have moved, shifted, or adjusted themselves to find their favorite spot to thrive. Caretakers still have to spend time throughout the year quashing invasive plants who have dropped in and removing trees whose seeds were brought in by neighborhood squirrels. Those trees are a by-product of the positive impact the garden has in attracting butterflies and other wildlife.
Visitors to the site will find a sign mapping out the original garden plantings. While some of the originals have moved, most can still be identified using the sign. Next time you travel on Victory Drive, look for that beautiful water purification system growing on the east side and wish it a happy 10th anniversary.