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Saturday - March 27, 2010

From: Dubuque, IA
Region: Midwest
Topic: Rain Gardens, Erosion Control, Grasses or Grass-like, Wildflowers
Title: Landscaping recommendations for site in Dubuque, IA
Answered by: Barbara Medford


I need a seed recommendation. Here are the variables: Location: Dubuque, IA (east Central Iowa) Soil type: Sandy to sandy and gravelly. Part is a riverbank facing east. Steep bank then flat to the water. Floods and gets covered with water in spring on the flat area. Orientation: East, north and Northwest Other thoughts: Some flat areas and some very steep areas. Will want good, deep root structure to stabilize soil and prevent erosion from hills. Fast growing and starting. Lots of weeds and brush to compete with Not too tall. Difficult area to mow so would like to keep it low maintenance Maybe native grass or wildflowers What else do I need to know or what other questions do you have?


Whoa! This is not a question; this is the study plan for a two-semester course in landscaping. When you say you need a seed recommendation, we are envisioning a packet of mixed seeds that, when scattered around the property, will cause plants appropriate to an eroding bank and floodplain to successfully deal with those problems. The plants emerging from this will include no invasive weeds and will crowd out invasive weeds already there. They will, of course, be evergreen and bloom most of the year in USDA Hardiness Zones 4b to 5a, with average annual minimum temperatures of -25 to -15 deg. F. These seeds will also produce plants that flourish in sun (6 hours or more of sun a day), part shade (2 to 6 hours of sun) or shade (less than 2 hours of sun) and need neither fertilizing nor supplementary water (when they are not being washed away on the floodplain).

Sorry, perhaps we exaggerate but we do want to emphasize that you are looking for an easy quick fix to a difficult situation. The Mr. Smarty Plants team is composed of mostly gardeners, mostly volunteers, mostly without the kind of resources to make recommendations on land we have not seen, the size of which and the available sunlight are unknown, and the use to which the property is to be put not stated. We would strongly recommend you consult a trained, licensed landscape architect who can actually survey the land, and give you concrete advice. Beyond that, about all we can do is give you ways to use our Native Plant Database and How-To Articles to make your own selections of seeds and/or plants to suit your diverse purposes. 

To begin with the bank, to stabilize the area we recommend grasses for controlling erosion because of their extensive fibrous root systems that serve to hold the soil in place.  You can probably buy plugs of the grasses, but the cheapest thing to do is to throw out some seeds. However, just throwing grass seeds over the side of your bank may not work very well.  The seeds need moisture to germinate.  If the moisture comes in the form of rain, it is likely to wash the seeds down the bank into the floodplain and thence the river before they have a chance to germinate and take root.  You might consider an erosion control blanket.  The erosion-control fabric works by slowing the runoff water and allowing sediments to fall out rather than be washed away. Seeds are sown under the erosion-control material and grow up through the matting when they germinate. You can also insert plants into the soil by cutting through the matting. The roots of the plants that are growing through the erosion-control material anchor the soil to stop the erosion. If you use erosion-control blankets made of biodegrable material, they will eventually disappear leaving the plants to control the problem.  Many nurseries carry this erosion control fabric. You could also include low growing shrubs and other perennials in the mix with the grasses.

Concerning the floodplain, instead of referring to it as a floodplain, try calling it a Rain Garden. Sounds better, can be very lovely, and is a widely used technique for areas that are often wet. We have a How-To-Article Water Gardening that will give you some ideas on how to treat this area, but that is not exactly what you want. What you want is a wetland or a rain garden, with plants that can both withstand dry weather as well as having their feet in standing water for a short period. The rain garden is not only a way to deal with streams of rain water and with saturated soil, but also helps to filter out pollutants and filter the water before it goes rushing off to lakes and your water supply. Here is an article from Rain gardens of West Michigan with some basic information to get you started thinking in that direction. The best reference source we found was from the Wisconsin Department of Natural Resources Rain Gardens, a How-To Manual for Homeowners. It is fairly lengthy, and probably involves more than you actually need or want to do for your problem area, but it has good explanations of why a rain garden is important to water and soil conservation and quality of our water supply, while giving you an attractive, useful area in your yard. This website Native Rain Gardens makes our point about native plants. In the same vein, please read our How-To Article A Guide to Native Plant Gardening.

You mentioned the possibility of wildflowers, as well. Read our How-To Article on Meadow Gardening to get some ideas on that.

Now you need to select some plants for this project. You must first decide what sort of plants you need-shrubs, grasses, perhaps small trees for each area. Also for each area you will need to know how much sun that area receives during the day. We consider "sun" to be 6 or more hours of sun a day, "part shade" 2 to 6 hours of sun and "shade, less than 2 hours of sun. Since so many variables are involved, we are not going to attempt to give you a specific list, but show you how to use our Native Plant Database to find the appropriate plants for your area and climate. On that page under COMBINATION SEARCH, select your state, the type of plant you are searching for under Habit or General Appearance, the amount of sunlight available and possibly the soil moisture. When you click on SUBMIT COMBINATION SEARCH, you will get a list of the plants in the chosen category that fit the characteristics you have selected. Following the links to the page on each plant will give you more information and pictures. If you have difficulty locating the plants you want, go to our National Suppliers Directory, type in your town and state in the "Enter Search Location" box and you will get a list of native plant seed suppliers, plant nurseries and landscape consultants in your general area. All have contact information so you can check with them in advance on availability and services.




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