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Home • Field Notes • Your Backyard and the Environment
Your Backyard and the Environment
Winter 2004-2005 Newsletter
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What is a Rain Garden? A shallow depression in your yard that’s planted with native wetland or wet prairie wildflowers and grasses. It is typically installed at the end of your rain gutter between your house and a storm drain. How do I make a Rain Garden? Dig a shallow depression, as large in circumference as you’d like. Direct your downspout or sump pump outlet to your Rain Garden depression, either by digging a shallow swale for water to run into the depression, or by piping the runoff through a buried 4-inch black plastic drain tile available at any home center. Populate your Rain Garden with native forbs and grasses that can tolerate wet feet. Water the new planting every other day for the first two weeks or so, until they show that they are growing and well-established. Once established, the plants will thrive without additional watering. Fertilizers are not necessary or recommended. Where should I put my Rain Garden? Keep it at least 10 feet from your house. Pick a naturally low spot in your yard, and direct the water into it. It’s best to choose a location with full sun, but if that’s not possible, make sure it gets at least a half-day of sunlight. During heavy rains, your depression will fill up and overflow. Make sure this overflow drainage follows the drainage pattern originally designed for your lot. Test this by filling your depression with a garden hose and watching the overflow. You don’t want to flood your neighbor’s yard! If you need to, dig a shallow swale to direct overflow water toward the street or other downhill areas away from buildings. How deep should I make my Rain Garden? A depression of two to six inches will suffice if you don’t want standing water. If you do want standing water, dig your depression deeper, perhaps down to 18 inches in the deepest spot. Slope the sides gradually from the edge to the deepest area. If you have heavy clay soil, it may well hold water without a liner. You can test this with you garden hose, too. If your soil won’t hold water, purchase a plastic liner to hold the water in deeper areas, and install your plants around the edges of the liner. A few more tips… Try not to spread or spray lawn fertilizers too close to the Rain Garden. Fertilizers will stimulate weeds and create competition for the native plants. Don’t worry about mosquitoes. If swallows and dragonflies don’t take care of them you can buy a ‘mosquito dunk’ (containing organic bacteria Bt) to kill mosquito larvae in your areas of standing water. Leave the dead vegetation to over winter in your Rain Garden. The stalks will provide some food and shelter for wildlife and add textural interest to the winter landscape. Come Spring, mow and remove dead vegetation, or if possible, burn it off. Native plants are adapted to fire and won’t be hurt by it. For more information: Go to Partnership for Rain Gardens or simply type ‘rain gardens’ into your favorite search engine on line. There is a vast amount of information available on the web. (Information provided courtesy of Applied Ecological Services,
Inc., Perenial Garden Design Sheet #1) |
This past summer I attended a conference in Madison, Wisconsin, on native landscaping and heard several interesting presentations.
The one that excited me the most was one presented by Evelyn A. Howell, who is head of the Landscape Architecture Department at UW-Madison. Her presentation was entitled “Environmental Principles for the Backyard.”
She did an excellent job of showing how what we do in our own backyard interacts with the overall environment.
“Your yard, no matter how big or how small, is part of a dynamic ecological landscape of interconnected parts: the biosphere (life), atmosphere (air), lithosphere (rocks), and hydrosphere (water),” was her opening remark.
“The interconnections include Flows (one way transfers) and Cycles ( a series of reciprocal transfers, in which things are passed from one component to another - e.g. biosphere to atmosphere – and may change state – e.g. gas to liquid – but don’t leave or enter).”
Cycles are especially important as they usually involve the continuous recycling of a limited earth resource. Ms. Howell dealt with the Nitrogen, Carbon, and Hydrologic cycles and also with several topographic and biodiversity issues relevant to backyard landscaping.
With my limited space and knowledge, I will attempt to deal only with the Hydrologic – The Water cycle.
The earth has a limited and finite quantity of water that is continuously recycled. In the water cycle, energy from the sun drives evaporation, whether it is from oceans, lakes, or treetops. Our sun also provides the energy that drives the weather systems which move water vapor (clouds) from one place to another.
Once water condenses, gravity takes over and the water is pulled to the ground. Gravity continues to operate, whether pulling water underground to become groundwater or across the surface to become runoff.
Lakes, ponds and wetlands form where water is temporarily trapped. The oceans are salty because any minerals picked up as the water runs to the ocean will add to the mineral content of the water, but water cannot leave oceans except by evaporation, and evaporation leaves minerals behind (thankfully).
Thus with a pristine earth, we had a continuous pure water recycling system; evaporation, condensation /rain, runoff and groundwater recharge. Introduce modern man and at least two things are disturbed.
Pollutants (such as acids) that we introduce to the atmosphere are picked up by rain water as it falls to the ground, resulting in less than pure rain water. Secondly (and I think more importantly), our disturbance of the earth by building structures, roadways, parking lots, etc. has greatly increased water runoff.
And, the chemicals that we use on our lawns and fields and roads and highways, etc. means that this runoff water has the opportunity to pick up lots of bad stuff before it finds its way into our rivers, our lakes, and eventually our oceans.
At America’s River Museum in Dubuque, they have a wonderful interactive display that vividly demonstrates the runoff problem by describing the huge “Dead Zone” in the Gulf of Mexico caused by the chemical load transported down stream by the Mississippi River and finally deposited in the Gulf. Disturbingly, awesome!
Evelyn Howell proposed that we help solve this runoff problem by focusing on our own property. She proposed that we adopt a “Best Management Practice (BMP)” for managing water runoff from our yard.
This BMP asks that we “Strive to achieve the goal that yard runoff be no greater than what it would have been under pristine conditions”. She also stated that the University of Wisconsin had recently adopted this BMP for all new campus construction.
Wow, was I impressed! If they can figure out how to do that for large university buildings in a space-limited environment, I should be able to figure out how to come close to that goal in my yard. But, how?
The first thing that comes to my mind is a restaurant in Door County, Wisconsin, located along the main road where one sees goats grazing on the sod-roof. This is probably one approach, but not very practical, I’m afraid. There are other well documented and proven ways. One thing that we all can do is to use fewer chemicals on our lawns. This does nothing to reduce runoff but certainly lessens the bad impact of runoff.
If you have a gravel driveway that has not yet been paved over with asphalt or concrete, you may want to think about leaving it as a gravel drive. The object is to redirect water that would run off your property and to get it to filter down through your land to become clean groundwater.
We are critically dependent upon groundwater. It is the source of the well water that serves many of our homes. A gravel drive is porous and allows water to filter through it; an asphalt drive generates oily runoff. If you must have a paved drive, porous paving options that use a permeable material over a stone reservoir could be considered.
See www.greenworks.tv/stormwater/porouspavement/ for more information on this technology. If, like me, you have already had your asphalt job and exacerbated your runoff problem, then other options must be considered.
These options include Rain Gardens, Bioswales, Rain Barrels, and expanding your use of deep-rooted native vegetation. Rain Gardens are just what they sound like — gardens that soak up the rain water, mainly from your roof, but also from your driveway and lawn.
They are landscaped areas planted with deep-rooted wild flowers and native vegetation to replace areas of lawn. The gardens, strategically placed in locations that are slightly depressed in elevation, fill with a few inches of water and allow the water to slowly filter into the ground rather than running off elsewhere. The native plants have deep root systems that die off and regenerate over time, providing filtration channels to the groundwater below. For more information on rain gardens I suggest visiting the following two web sites:
Also the Wisconsin DNR has a wonderful booklet entitled “Rain Gardens, A how-to manual for homeowners”, that should be available through their web site, or through the University of Wisconsin Extension Service.
Bioswales are for more high-volume runoff management arrangements using vegetation filled “ditches” as filters, and beyond the scope of this article. Rain barrels are back in style and can be used effectively to manage low volumes of water runoff by storing water for local use.
They can be used in conjunction with rain gardens so that you first fill your rain barrel then overflow to the rain garden. The Rainscapes web site referenced earlier has very good information on rain barrels and overflow designs.
The use of native plants and less turf grass on your property anywhere means more water will be absorbed and filtered into the earth because of the deeper root systems.
Rain gardens are a particular adaptation aimed at pooling water temporarily in strategic locations for later absorption. But anywhere that you use native plants in your yard, the runoff will be less than it would be with turf grasses.
“We borrow the earth from our grandchildren; let’s not default on the loan.”
—Randy Downing