123 Garden Guide

Spring Time Lawn Care Professor Mel 3/22/2004 RAKING Gardeners may start work on their lawns as soon as weather permits. A thorough raking to clean off leaves, twigs and other debris is the first project. Raking the lawn gently to remove this type of debris is usually sufficient. Very hard and vigorous raking is not only unnecessary in most cases, but this can also pull out young grass seedlings or shallowly rooted grass plants.   LIMESTONE APPLICATIONS Turfgrass will not grow well in soil that is too acid (low soil pH). A soil pH between 6.5 and 6.8 is ideal for most turfgrasses. When the pH is in this range the turfgrass plants will be able to use fertilizer and nutrients in the soil efficiently. The only way to determine accurately whether a lawn needs limestone and the correct rate to apply is to have the soil pH tested. Have the soil pH tested about every 2-3 years to determine if the soil pH needs to be corrected with an application of limestone. Limestone applications can be made anytime during the spring or at other times during the growing season.  FERTILIZER APPLICATIONS In most cases a heavy early to mid-Spring application of a fertilizer (especially nitrogen) can lead to certain disease problems and make your turfgrass shallow rooted. Both results can lead to serious trouble for your lawn during the summer and therefore applications of fertilizer at these times is not suggested. If a late fall (late November) fertilizing of the lawn was not done and the lawn shows a need for fertilizer, apply 1/2 the recommended rate of fertilizer in the early spring (April-early May), late summer (Labor Day) and late fall (Thanksgiving Day).   RESEEDING, OVERSEEDING RENOVATION How much grass seed is needed for spring improvement of an established lawn? None at all unless there are bare spots, in which case, each area should be prepared and seeded as you would a new lawn. A common practice of throwing grass seed on a thick established lawn is wasteful and not beneficial. The grass seedling will have little or no chance of establishing and competing with the surrounding grass. If the lawn is thin overall then overseeding may be helpful. The best time to renovate large areas of your lawn by overseeding is in late summer (August 20-October 1), not during the spring. If overseeding is necessary in the spring because of winter kill, etc. it should be considered as soon as the soil dries adequately enough to be walked on in April. It is very important to first identify and then correct factors contributing to the overall poor growth before considering overseeding. Overseeding without taking this into consideration is unlikely to produce desirable results.   THATCHING Dethatching a lawn each spring should not be considered a routine maintenance chore. It should only be considered when it has been determined that the lawn has a true thatch problem. Since the dethatching process injures good turfgrass it should be done in the early spring or fall when weather favors a fast recovery of the injured turf. There are many misconceptions about thatch, its causes and problems. First, thatch is the accumulation of dead and dying turfgrass plant parts, such as roots and stems. The thatch layer is dark in color and develops above the soil surface and, in many cases, contains turfgrass shoots. Thatch is not the accumulation of grass clippings from mowing the lawn as some believe. A layer of thatch less than 1/2 inch thick does little, if any, harm. However, when this layer is in excess of of 3/4 inch, the turf is more susceptible to disease and insect problems and has less wear, drought, heat, and cold tolerance. Also, thatchy turf can be diffucult to water since thatch can become water repellent when dry. Factors that lead to a thatch buildup are acid soils with a pH less than 6.0, too little or excessive fertilization, poor drainage, compacted soils, droughty conditions, and overwatering. When excessive thatch develops, several steps should be followed to help try and eliminate or reduce the problem. To be sure you have a thatch problem, take several wedge-shaped slices, including the surface soil layer, at several locations. Inspect the samples to determine the thickness of the thatch. A layer less than 1/4 inch is considered acceptable. When the layer is between 1/4 and 1/2 inch thick, you may want to slow down further buildup by eliminating the causes of the thatch. A 1/2 inch or thicker layer of thatch requires a slow but careful process of removal. The repeat use of a dethatching machine along with eliminating the causes of the thatch buildup can, with time, reduce the thatch layer. Even though it may seem that you have removed a lot of thatch during the dethatching operation, it generally takes several dethatchings to significantly decrease the thatch layer. The use of a core aerator can also help in reducing thatch layers.  CORE AERATION Core Aeration is done with a machine which removes or pulls a series of soil plugs out of the lawn. The plugs vary in diameter and depth depending on the make of the machinery. These plugs remain on the lawn where they are lightly broken up and the soil is worked back into the lawn with a metal drag mat or metal rake. The use of a "spiker" is not the same as using a core aerator. Spikers only punch holes in the soil and don't provide the benefits of a core aerator. Some benefits of core aeration are improved water penetration, improved fertilizer and limestone penetration, improved turfgrass root and shoot growth, and soil cores left on the surface increase microbial activity to help decompose thatch. Many feel that core aerators are more useful than dethatchers in helping reduce thatch layers. Since core aerators injure turf roots the process should be done when the turf is growing vigorously in early spring or fall so the turf has ample time to recover before dry or very cold weather. Like dethatching, core aerating does not need to be considered a routine chore every spring.   IRRIGATION In New England rainfall provides sufficient quanities of water for an established lawn during most spring seasons. For this reason the need for additional irrigation to established lawns is usually not necessary. This is true during April and most of May. Automatic irrigation systems can be serviced and turned on so they will be ready to go if they are needed. In most cases consider setting the system clock on MANUAL and utilize it only when a true need for supplemental irrigation exists.   GRUB CONTROL Grub control in the spring should only be considered when the lawn suffered from serious grub injury the previous fall. Grubs overwinter and come back to the surface in April to feed for a short period of time. If your lawn was not seriously injured by grubs the previous fall or if there was no grub problem at all at that time then a grub problem cannot exist in the spring. If a treatment is needed apply it as soon as the grubs near the surface in April. No spring-applied product will control grubs which will hatch in late summer. Those grubs are responsible for the damage in late summer-fall. The most effective time of the year to control grubs is mid-August through September.   BROADLEAF WEED CONTROL Broadleaf weeds such as dandelions, chickweed, spurge, etc. can be controlled in the spring (April and May)with the use of an appropriate broadleaf herbicide(weed-killer). These materials will kill weeds which are present at the time of the application. They do not prevent weeds from appearing in the lawn if the weeds are not already present. In other words the herbicides are not preemergent weed killers. Remember, one of the best weed controls is to encourage a good, thick stand of turf by following correct maintenance practices.  CRABGRASS CONTROL Unlike broadleaf herbicides, preemergent herbicides are available for the control of crabgrass in the lawn. When applied properly, and at the correct time of year, these materials will kill germinated crabgrass seedlings before they emerge from the soil. Preemergent herbicides used to control crabgrass are usually applied between early April and into May. A good way to determine when to apply a preemergent crabgrass herbicide is to apply it after the common yellow flowering shrub, forsythia, finishes blooming but before the common purple or white flowering shrub, lilac, starts to bloom. Remember, that one of the best crabgrass controls is to encourage a good, thick stand of turfgrass through proper maintenance practices.   ROLLING Rolling a home lawn is not necessary in the spring unless the lawn has areas which have been raised by frost heaving over the winter. As a regular maintenance practice, use a roller at most only once a year. If soil heaving has been a problem you may choose to roll the lawn with a roller just heavy enough to press the turfgrass plants back into the soil. Do this in early spring before growth starts, when the soil is dry enough to crumble easily in your fingers. Rolling often will not benefit the lawn and if rolling with a heavy roller is done in clay soil or overly wet soil more damage than good can occur. Spring rolling is the least important chore and can be omitted without serious harmful effects.

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