Growing Wetland Plants To Improve Water Quality
A Vegetation Backgrounder

Project Description

The aquatic vegetation plantings are one part of the Twin Lakes Subwatershed Improvement Project - a water quality improvement project supervised by the Minnehaha Creek Watershed District (MCWD). The project is a coordinated effort by the Clean Water Partnership (CWP), which includes representatives from the MCWD, the cities of Minneapolis and St. Louis Park, the Minneapolis Park and Recreation Board, Hennepin County and the Minnesota Pollution Control Agency.

Earlier components of the project included construction of wetland detention basins. Wetlands are a key to many of the MCWD's and CWP's water quality projects because they naturally filter and cleanse urban stormwater.

The Chain of Lakes Clean Water Partnership is a seven-year initiative to improve water quality in the Minneapolis Chain of Lakes. It is one of the largest urban watershed-restoration projects in the country and includes wetland restorations, storm sewer improvements and public education.

The project is funded and sponsored by the cities of Minneapolis and St. Louis Park, Hennepin County, Minneapolis Park and Recreation Board, Minnehaha Creek Watershed District and Minnesota Pollution Control Agency.

Where are the plantings?

Plantings will take place just west of Cedar Lake in Minneapolis and St. Louis Park. Aquatic vegetation will be planted at Twin Lakes and Twin Lakes Park, while both aquatic vegetation and shoreline vegetation plantings will take place at Cedar Meadows. See attached map for specific locales.

Who is involved?

• The Minnehaha Creek Watershed District is directing the project, with help from members of the Clean Water Partnership and from the Cedar-Isles-Dean Neighborhood Association (CIDNA).
• The Loring-Nicollet-Bethlehem youth volunteers, a group of 13- to 17-year olds with an interest in the environment and horticulture, will help with plantings at Cedar Meadows.
• Master gardeners from Twin Cities garden clubs will help train the youth volunteers and oversee the plantings.

How Do Aquatic Vegetation and Wetlands Enhance Water Quality?

While the MCWD and CWP tackle major water quality projects, backyard gardeners who have bodies of water on their properties (ponds, creeks, etc.) can use the same vegetation techniques to protect water quality on their properties and beyond.

By planting more than 19,000 select plants, the CWP will complete shoreline and wetlands environs that naturally filter and cleanse urban stormwater. Wetlands effectively reduce levels of sediment, lawn pesticides, yard waste and nutrients - especially phosphorus - before they can impair lake water quality.

These urban water bodies need special wetland species - plants that are equipped to take on urban stormwater. These plants will grow rapidly and establish a defensive front against pollution. Their roots host a beneficial bacteria that captures impurities.

Eventually, wetlands can improve the water quality of Twin Lakes and Cedar Lake by removing up to 30 percent of the phosphorus and dissolved inorganic nitrogen. Wetlands also are a haven for vast numbers of wildlife. In fact, the biodiversity of wetlands in the Midwest is greater than any other temperate plant community.

This particular project won't solve all the water quality problems. The combination of wetland ponds and sediment removal Best Management Practices has an immense, positive cumulative effect on improved water quality.

Approximately 19,000 plants (a mixture of 2" and 4" potted plants) will be placed along the shorelines with small hand trowels. The trick is where to install them. Each of the 20 species of plants has specific planting requirements to help them thrive. Some live in the drier pond edges. Others must be planted in deeper water. The diagram below provides a cross section of where varieties should be placed.

Protective barriers are built to keep Canadian geese, musk rats, white-tailed deer, carp and rusty crayfish from disturbing the plants, and to dissuade humans from trampling or pulling them.

The aquatic plants can be purchased at local nurseries belonging to the Minnesota Native Wildflower/Grass Producers Association. For a free listing of nurseries, services and phone numbers, write to the Minnesota Native Wildflower/Grass Producers Association, Route 3, Box 163, Winona, MN 55987.

Once the plantings are complete, the MCWD will routinely monitor the sites to evaluate the vegetation growth. Gardeners should keep in mind that establishment of wetland vegetation often takes more than one season. Many factors affect growth, including quality of rootstock, installation methods, weather conditions, rough fish and wildlife impacts.