Eco-Answers from the Pros: Alternatives to Grass on a Hillside

I am on the board at a 64 unit condo community in St. Paul, MN. We have a huge hillside with regular grass, which means weekly mowing. The hillside is eroding in some sections. The shaded areas have very little grass at all. How can this be converted to a low mow fescue? Or, what other options would there be? It’s very costly just to mow the area due to the slope. The current board is very environmentally conscious. We don’t want to use chemicals and want to restore/use some type of native options.

First, I think it is most important to determine what the goals for the space are. Is turf a priority even if it is not actively used? Is improved habitat for pollinators, song birds, etc. the main priority? Or is it appropriate to transition the space to native vegetation and allow nature to do what it does best – grow, and then implement an invasive species management plan?

Briefly, there are options to address the problems of the conventional turf slope in both sun and shade. I always like to complete a complete site analysis before recommending solutions. The questions we ask may include, but is not limited to, the following:

  • What are the source waters and what are the potential rates of surface flow? Source water influencing spaces may include hard surface runoff (i.e. structure roof areas, patios, paths, roadways, etc.), naturally occurring springs, and adjacent construction activities. (Wehave come across a few projects where adjacent construction activities have created devastating effects to normally secure slopes, vegetation, etc.)
  • Does the slope allow for machine access to install swales on contour (key line swales) and/or remove non-desired vegetation? We are not in favor of using any herbicides, but in certain situations they may be the most viable solution for revegetating areas.
  • What are the existing soil types, and how deep do they go? Stabilizing topsoil on a bedrock slope has its own challenges, and knowing St. Paul along the Mississippi river area, there are numerous areas where the topsoil is relatively shallow before bedrock and outcroppings are found.
  • Are there visibility requirements? Road easements, intersections within certain distances may limit what types of vegetation can be used for stabilizing surfaces.
  • What is the existing tree canopy composed of? The existing trees can aid in determining what types of understory plantings will perform best.

Slope stabilization techniques can be devised and implemented once some general information and answers to the basic site questions are available. First, I always recommend using a layer of composted leaf fines (not completely composted so there are not excess nutrient issues) to aid in holding a bit more moisture on site for seed germination. Stabilization of the slope includes some, if not all, of the following for most of our projects:

  • Brush wattles
  • Burlap wattles
  • Erosion blankets (If at all possible, try to use netless due to plastic netting persistence issues)
  • Contours on slope if machine access is available
  • In some situations, geo engineered textiles may be the best option to hold seed and plantings on slopes during establishment (if the slopes exceed a certain percentage)

Finally, determine what the slope will be revegetated with: low mow, native, or both. I like the idea of low mow fescue mixes, and I use them frequently in most of the turf areas on our projects. That being said, I have run into some issues with municipalities citing property owners with “failure to maintain lawn” warnings for the no-mow grass mixes, similar to what we worked through when landscapes were being restored to native prairie mixes in the mid-1990s. Short-grass prairie may be a good option for full sun near city streets, whereas tall-grass mixes may be appropriate for other areas. I frequently use a variety of sedges (Carex spp.) for shady locations and the species can be determined based on soil types and moisture levels. I always recommend using cover crops of winter wheat or oats for any of our restoration areas to act as the intermediary for soil stabilization until the desired species establish.

Perhaps the most important, and most overlooked, aspect of any revegetation project is short-term and long-term maintenance. Make sure a plan is in place to maintain the investment. Conventional mowing may be reduced, but periodic mowing, pulling, and burning (if possible) of vegetation may be needed to control woody and invasive species in the desired vegetation.

     Daniel Peterson, Habadapt Landscape Design, Minneapolis, MN

There are many good options for replacing a traditional lawn with groundcovers or with a no-mow fescue. Following are a few resources that might be of help:

     Penny Lewis, ELA Executive Director

ELA members have spent hundreds of hours learning the best ecological solutions to problems in the landscape. You can benefit from all that accumulated knowledge by posing a question to our experts. If you are stumped by a problem in your landscape or are looking for a second opinion on a potential solution, ask ELA’s Eco-Pros. Send your question to ela_new@verizon.net. And if you need additional help, refer to the listing of ELA Professionals.

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