By Frank Wertheim, Extension Educator, University of Maine Cooperative Extension.
Reviewed by Barb Murphy, Extension Educator, University of Maine Cooperative Extension; Amy Witt, Horticultural Professional, University of Maine Cooperative Extension; Kate Garland, Horticultural Professional, University of Maine Cooperative Extension; and Gary Fish, Maine Board of Pesticide Control.
Low-input lawn-care practices involve reducing the amount of pesticides (mainly weed and insect killers) and fertilizers that you put on your lawn. Over 6.2 million pounds of yard-care pesticides were brought into Maine in 2007. This number has increased seven-fold since1995 and coincides with an explosion of yard-care companies in Maine. During the same period there has also been a sharp increase of homeowner/tenant use of lawn care multi-step programs containing fertilizers and pesticides. Misuse of lawn-care pesticides and fertilizers negatively affects our water quality. At risk are lakes, streams, and eventually the ocean—the endpoint of all watersheds. The goal of a low-input lawn is to create an ecologically diverse lawn that will look green and healthy without intensive fertilizer and pesticide treatments. Follow these basic principles to create and maintain a healthy lawn while reducing or eliminating fertilizers and pesticides.
Give your lawn a good raking with a flexible-toothed rake in early spring to remove thatch. Save what you rake up for your compost pile. Removing thatch helps your lawn breathe and allows for new shoots to fill in open spaces. You may wish to lightly overseed after de-thatching to introduce new grasses in the bare areas (see “Overseed your lawn” below).
The Analytical Laboratory and Maine Soil Testing Service at the University of Maine conducts soil tests. Review University of Maine Cooperative Extension bulletin #2286, Testing Your Soil. To get a copy of this bulletin, as well as a soil-test box and form, contact your local UMaine Extension county office, or call 800-287-0274 (in Maine). The test results will tell you about your soil pH, nutrient levels, and the percentage of organic matter. The report will give you recommendations for optimal plant health. If you prefer, organic fertilizer recommendations can be requested when you send in your soil sample.
The pH of the soil (acidity level) for lawns should be in the range of 6.0 to 6.5. Most lawns in Maine have soils that are too acidic (pH is too low). A soil pH of 5.5 or lower favors weed growth more than grass growth. Herbicides can be used to kill weeds; however, if the pH of your soil is not optimal the weeds will simply regrow. Adjusting the pH to within the range of 6.0 to 6.5 will help create an environment that allows the desirable grasses to outcompete and crowd out the weeds. Lime or unleached wood ash can be used to raise soil pH: your soil test results will give you recommendations in terms of pounds of lime or wood ash per thousand square feet needed to reach the desirable range. Occasionally, lawn pH is too high. This is often the case when homeowners add lime or wood ash several years in a row without having a soil test. Elemental sulfur or aluminum sulfate is used to lower soil pH. These amendments may be applied at almost any time of the year.
Optimal topsoil depth for grasses is twelve inches, but that amount of soil is unrealistic. Lawns should be grown in at least four to six inches of topsoil. If your topsoil falls short of that, you can build it over time by top-dressing your lawn with mixed compost and loam, up to a half inch a year. Mixed compost and loam, blended to about 50 percent each, is available from many of Maine’s commercial compost facilities.
If you do decide to top-dress your soil with mixed compost and loam, you may also want to overseed the lawn lightly to introduce species with reduced fertilizer and pesticide needs. Overseed just before spreading the compost/loam mix to encourage good seed germination. This can be done any time from early spring through early fall, though you will get better seed germination results in late summer/early fall (August-September).
If your topsoil depth is inadequate, another way to boost your soil organic matter and nutrient levels and improve the vitality of your lawn is to top-dress with a good-quality compost. Spread two yards of compost per five thousand square feet of lawn, raking it out as evenly as you can to a depth of no more than a half inch. Many garden centers sell compost in bulk, and some even have spreaders you can borrow or lease to help with the job.
If you add compost every year, you will need to test your soil to monitor your phosphorus level, which can become excessive with repeated compost applications. Excessive phosphorus can create a risk for runoff into freshwater bodies, where phosphates can contribute to algal blooms.
Too much compost (added several years in a row) can also cause a rich soil layer to develop at the surface,which may cause the grass roots to stay very shallow. If layers begin to develop, you may need to till the soil and reseed the lawn.
Most lawns will do just fine if fertilized only once a year, especially if you seed new grass varieties that have been developed to thrive in a lower-nutrient environment. Lawns older than 10 years don’t need to be fertilized because they naturally recycle nutrients. Many people choose to skip fertilizing altogether and keep their lawn health robust by using grass varieties with low fertilizer needs, maintaining the correct pH (6.0 to 6.5), and ensuring that their lawn has adequate soil organic matter. If you choose to fertilize, apply fertilizer between Labor Day and Columbus Day according to your soil test results. Because Maine’s soils are usually rich in phosphorus, use phosphorus-free fertilizer, unless you have a soil test that indicates inadequate phosphorus levels in the soil.
Set your mower blade at three inches and mow regularly with a sharp blade. Try not to cut off more than one-third of the grass blade in each mowing, e.g., let the grass grow to four inches and then mow off one inch. Most people mow their grass too low, which stresses the turf, making it turn brown and become more susceptible to drought, insects, and diseases. Let the clippings lie on the lawn, as they are a high-quality, low-cost fertilizer and do not contribute to thatch. Thatch build-up is more common in an intensively managed, highly fertilized lawn. It will not build up to a point where it will cause problems in a low-input lawn.
If you don’t water your lawn, it will naturally brown and go dormant in the heat of the summer. It will green right up in the fall when rains return. An added benefit is that Japanese beetles will look for someplace else—a lush, over-fertilized and over-watered lawn—to lay their eggs, perhaps resulting in reduced or tolerable levels of grub-feeding damage in your lawn.
If you choose to water (when rains do not provide an inch per week), do not water more than twice weekly. Water deeply enough (about a one and one-half inch each time) to train the roots to grow deeper and form healthier plants that will be more resistant to drought and disease.
Aerate your lawn once every one to three years, in late August or early September. A core aeration machine pulls out tiny plugs from the soil, which helps the lawn breathe. In addition, the soil plugs left behind help break down thatch. You can rent an aeration machine, or have a landscaper aerate for you. A low-input lawn can be aerated less often than a highly managed lawn, as thatch build up will become less of an issue. Again, thatch is rarely a problem in low-input lawns.
Overseeding your lawn is a great way to introduce new turf-grass species that have been adapted to grow well in a low-input lawn environment. Overseeding works really well if grass seed is spread just after aeration. Many of the seeds will fall into the tiny holes left behind by the aeration machine where it is cool and moist, facilitating good seed germination.
Seed is also the best defense against weeds. Any time you find a bare spot or remove a weed, be sure to reseed those areas. A light sprinkling of a fast-germinating grass type, like perennial ryegrass, is a good choice to fill the gaps before a new weed has a chance to take over. This can be done in the spring, summer, or fall, though the best time to seed a lawn is late summer to early fall (August–September), as weed pressures are reduced at that time of year and soil temperatures are still warm enough for quick seed germination.
Visit the Maine state Yardscaping Partnership website to find a list of newly developed grass species that thrive in a low-input lawn environment. This resource also lists endophyte-enhanced grasses that are naturally resistant to surface-feeding insects and tolerate drought conditions.
There are several species of large, C-shaped white grubs that feed on and damage turf roots, such as Japanese beetle, June beetle, European chafer, and Asiatic garden beetle grubs. Beneficial nematodes, available through some garden centers and catalogs, have shown promising results in grub control. Another biological control organism, which is marketed as milky spore, is a microbial disease that has been licensed for control of Japanese beetle grubs. Milky spore is not very effective in Maine and has not been documented to give adequate grub control. It is also very expensive to apply. The good news is that many low-input lawn practitioners find that a minimally fertilized or unfertilized lawn attracts fewer grubs to begin with, and can tolerate a low population with little or no damage to the lawn.
Many people incorrectly assume that mole damage is a result of a high grub population in a lawn, while in reality moles feed primarily on earthworms. Using a pesticide (organic or chemical) to reduce grub populations will not reduce mole activity. Earthworm activity is very beneficial in creating a healthy lawn, and a small amount of mole activity will provide some free lawn aeration. Generally the mole holes and mounds that appear in spring after snowmelt can simply be raked over. In a couple of weeks the signs of them often disappear, and new grasses can take over any bare spots as grass plants send out new tillers and fill in. You also could spread grass seed over bear spots to help this process.
By following these practices, your turf-grass will thrive in a low-input and healthy environment, and in time will be able to outcompete or crowd out many weed species. Best of all, you won’t need to use any herbicides. You can hand-pull a few dandelions or other so-called weeds, if they bother you—but think about the beneficial effects that diverse species of plants in your lawn can have on the environment for your family, your pets, and wildlife.
Keep your lawn healthy the low-input way, and relax!
For more information: www.yardscaping.org
Information in this publication is provided purely for educational purposes. No responsibility is assumed for any problems associated with the use of products or services mentioned. No endorsement of products or companies is intended, nor is criticism of unnamed products or companies implied.
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