A walk through most neighborhoods in south-central and southern Illinois reveals the impact this summers heat and drought had on home lawns. Most area lawns are composed of cool season grasses such as Kentucky bluegrass and turf type tall fescue. In response to the summer's extreme environmental stress, grasses went into extended natural dormancy or in some situations died out as moisture was lost. However with milder temperatures and much needed rain, cool season lawns are beginning to grow and come out of dormancy. As new growth occurs there are several management steps to take this fall that will help your lawn recover more quickly and thrive next year. Some or all of the following recommendations for cool season lawn care may apply to your situation.
1. Control perennial weeds. Fall is the time to spray weeds such as plantain, ground ivy, dandelions, field bindweed, and thistles with a selective broadleaf herbicide such as 2,4-D. Herbicides applied now are more effective compared to other times of the year. By controlling perennial weeds, they will not be there to compete next year, or this year as lawns make growth, or compete with new grass in over-seeded areas.
2. Dethatch. Dethatching is the removal of accumulated dead grass under the green turf. On irrigated, heavily fertilized or improperly mowed lawns this accumulation can be significant. Excessive thatch of an inch or more will lead to shallow rooting into the thatch layer, making the turf more susceptible to drought. Thatch also harbors disease. Dethatching can be done fall or spring, removing about half an inch of thatch each time. A tine type dethatcher attachment, power rake or a vertical mower work well to dislodge the thatch. These can be rented at most rent centers. Dethatching is destructive and live grass roots and plants will also be removed, thinning the turf, so care must be taken not to "over do" it. Uplifted thatch can be picked up with a yard sweep or bagged with a mower.
3. Fertilize. Cool season grass peak growth is in the fall months. Timing fertilization early with this growth period is important, and it is usually done in September. For rapidly growing grass, nitrogen is needed and quick release materials such as 21-0-0 are effective as they become available soon after watering in. For non-irrigated areas, keep an eye on the weather and apply ahead of a predicted rainfall. A second application can be made again in late November. It is important not to over-fertilize, with the standard recommendation to apply only 1 pound of nitrogen per 1000 square feet of lawn area. As fertilizers vary in percent nitrogen, it is important to calculate how much of a particular material should be applied to a given lawn size. Most lawn fertilizers come with direction on how much area a bag will cover. Depending on your lawn square footage, calculate how much of the bag is needed. For example if the bag says it will cover 5000 square feet, and your lawn is 2500 square feet then you need half a bag. It is important to apply the amount needed evenly over the lawn. Set your spreader to a low setting and make overlapping passes in different directions until the full amount is used.
The November fertilization is considered a "winterizing" application. It should be made after top-growth stops or your last mowing. The fertilizer used should contain both nitrogen and potassium. Potassium will promote root growth through the winter months, and help the lawn get off to an early start in the spring. Slow release fertilizers are particularly effective winterizing formulations.
4. Aerate. Root oxygen availability is critical for good plant growth. Soils compacted over the season by heavy foot traffic and lawn mowers are limited in the amount of oxygen that filters into the grass root zone. Heavy clay soils are particularly subject to compaction. One method to loosen compacted soils is to aerate the lawn through mechanical coring. Coring aerates the lawn by removing small plugs of soil 1 to 2 inches long, and a half to three-fourths inch in diameter. These cores are lifted out and deposited on the surface where they dry and crumble, leaving a small hole in the soil. Though somewhat destructive, the benefits to plant growth far outweigh any damage done. Coring has the additional benefit of creating soil contact sites for new grass seed germination. Aeration should be done at least once a year. For heavier clay soils, a mid-spring aeration may also be needed. Avoid using spike-type aerators which simply poke holes in the soil. These are not as effective as plug aeration and can further compact soils.
5. Seed. Along with being an ideal time to promote existing turf growth, fall is also the best time to plant grass seed. Thin lawns can be over-seeded to thicken the turf, bare and damaged areas can be repaired, and brand new lawn areas can be seeded. Fall provides ideal soil and air temperatures for grass germination and growth, usually adequate rainfall, and less competition from weeds as compared to spring seeding. When seeding, select the appropriate type and variety of grass for the situation. As a general rule, turf-type tall fescues should not be mixed with Kentucky bluegrass. This is because tall fescue stands out in clumps in a bluegrass lawn and they differ in leaf texture. However both turf-type tall fescues and Kentucky bluegrass can be mixed with perennial ryegrass and fine bladed hard and red fescues. Mixes of grass types and blends of varieties, as well as pure seed are developed for various sun/shade levels and soil conditions. Choose according to your situation. For over-seeding existing lawns it is important to first determine which species dominates your lawn, and purchase a blend of that species. For example in a bluegrass lawn, select a bluegrass blend composed of several adapted varieties. This will help to diversify the grass stand and provide greater resilience to adverse environmental conditions.
When seeding always make good seed to soil contact. To over-seed into an established turf, use a power seeder which cuts small grooves and drops seed into the soil. This is more effective than just broadcasting seed on the surface. For patching bare spots or seeding new lawns, hand-rake seed into lightly tilled soil, and tamp down with a flat board or rolled to firm the site. Watering and keeping the area moist until the seed germinates is critical for good establishment. A light layer of straw will help hold moisture and encourage good germination on bare sites. All new grass requires fertilizer nutrients to get off to a good start. Fall fertilizer application should be made prior to over-seeding an existing lawn. For new lawns, a soil test that determines pH, phosphorus and potassium levels should be taken. Prior to planting, apply lime if pH is low and the soils are acidic (often the case in our region), and phosphorus and potassium if testing indicates a deficiency.
By following some or all of these measures, lawn areas can be greatly improved in the landscape. Now is the season for cool season turfgrass growth. Management with weed control, fertilization, dethatching, aeration, and seeding with adapted varieties will result in healthier grass and improved stand, and a turf better able to withstand the rigors of next years growing season. For more in-depth information on turfgrass varietal selection, establishment and care, visit the University of Illinois Department of Natural Resources and Environmental Sciences Extension Turfgrass website at: http://www.turf.uiuc.edu/extension/extension.html.
