Ecological Spring Lawn Care
There are a number of environmentally friendly practices that may be used to grow a healthy and attractive lawn. An important foundation is an understanding of the growth attributes of turfgrass, as well as of weeds, to inform action on appropriate practices and timing for fertilization and weed management. The active growing season of lawn grasses differs from that of many weeds; lawn care practices can be timed to maximize conditions that support a healthy lawn and minimize chemicals that ultimately pollute our streams, lakes and rivers.
The primary obstacle to weeds becoming established in your lawn is to maintain a healthy and thick lawn. To do this, good cultural and mechanical practices are essential. This includes maintaining a soil pH between 6.1 and 7.4, and proper mowing. Use a sharp mower blade to keep the grass at a height of three to four inches. It is best to remove no more than 1/3 of the height of the grass blades at each mowing.
Grass clippings decompose rapidly, provide some fertilization, help to retain moisture in your lawn, and do not contribute to thatch. Leaving the clippings on the helps protect the environment by reducing space needed for landfill.
Now that spring has finally arrived, these are steps to take:
Spring Clean-up:
Avoid working on a frozen or muddy lawn. This can break the crowns of the grass plants and compact the soil that supports your lawn. Most lawn grasses do not tolerate compacted soil, so the weeds that grow well under this condition will gain an advantage.
Crabgrass:
The ideal way to prevent crabgrass is to develop a dense lawn the previous season. This eliminates bare spots where crabgrass can get started. Crabgrass is an annual weed that spreads its plentiful seeds in the fall before it dies with the first frosts. These seeds wait for the spring, to sprout roughly around the time the forsythias bloom. If your grass is thin in some spots, this would be the time to begin overseeding to increase the turf density or apply a crabgrass pre-emergent (most pre-emergent herbicides prevent lawn grass germination). Once crabgrass germinates it can be very aggressive and difficult to manage, especially if it is widespread.
Fertilizer
Resist the temptation to apply fertilizer in early spring – wait until fall. Grass roots store nutrients in fall; in spring the plants convert nutrients, including any fertilizer you apply, to top growth. If you fertilize in early spring, you are forcing dense growth that is more susceptible to disease and requires extra mowing. Most lawns do not need more than one fertilizer application (a well-established lawn may not need fertilizer at all), applied in early fall. It is especially important to avoid fertilization and resultant fertilizer burn when the lawn goes dormant in the hot and dry months.
Dandelions and other broadleaved weeds
Broadleaved weeds in a lawn are generally grouped according to their growing cycle; annuals that emerge in spring or fall, and perennials, such as dandelions, that are present year round. The best defense against encroachment by these weeds is similar to that for crabgrass: a dense lawn that does not have bare areas where the weeds can get started. Mowing the grass high will help it to develop more roots and thicker crowns. If the lawn is thin, aggressive overseeding may help. You may dig out small patches of weeds by hand - be sure to remove the roots. As a last resort, you may consider a broadleaved herbicide (type dependent on which weeds are prevalent); these are applied to mature turfgrass in late spring.
Insect Management
Most insects observed on the lawn are not harmful. Those that cause injury have their own optimal timing for treatment – most occur in warm or hot weather. In particular, it is not effective to treat a grub infestation in early spring. Treatment with an insecticide may be warranted in late summer or early fall when the grubs are small, if there are patches with an average of more than eight to ten grubs under a one square foot cut-out.
Mitchell Bittman
Master Gardener withCornell Cooperative Extension of Rockland
References:
http://blogs.cornell.edu/horticulture/about/lawn/lawn-how-grass-grows/
Ecological Lawn Care, Mary Thurn, Cornell University, 2012
Turfgrass, UME, 2012, 313 - 339
Ecological Lawn Care, Frank Rossi, Ph.D., Cornell University, 1999
Weeds, UME, 2012, 259 – 281
