   Upcoming Cool Season Turf Maintenance - September 27, 2000 Jeff Schalau, County Director, Agent, Agriculture & Natural Resources Arizona Cooperative Extension, Yavapai County Fall fertilization and maintenance is key to year-round success with cool season turf grasses. Fall is also the season to seed cool season grasses to cover bare spots or establish a new lawn. Our most common cool season perennial turf grass species are Kentucky bluegrass, tall fescue, fine fescue, and perennial rye. You can think of fall as the beginning of these species' overall growth cycle. So, read on to ensure cool season turf success. First, some readers may be wondering if they have cool season turf. Cool season species are most healthy and vigorous in the fall and spring. In winter and summer, they maintain a green color, but are less robust in these seasons. Contrast these characteristics with warm season grasses (Bermudagrass, St. Augustine, buffalograss, zoysia, and grama) which are green up in the late spring, grow vigorously during summer, and fade to brown after the first frost. Warm season grass species have very different cultural practices. Many cool season lawns are a mixture of perennial rye, Kentucky bluegrass (KBG), and fine fescue. Treat this mix the same as you would a pure KBG lawn. The surefire way to determine if you have KBG, is to pluck a leaf blade and look closely at the leaf tip. If it has a "boat-like" shaped tip rather than a flat blade, then it is KBG. Fall maintenance of KBG in the Verde Valley is as follows: bare spots can be over seeded September 10-25 (a week or so later is alright too); sod should be laid between September 25 and November 5; nitrogen fertilizer can be applied in both October and November at a rate of one pound of actual nitrogen per 1,000 square feet (5 lbs ammonium sulfate 21-0-0; and dethatching/aerification should be done between October 1 and 10. More on when and why to dethatch/aerify later in this column. Tall fescue is usually used in areas where cool season grass is wanted, but a tougher turf is needed (ball fields, parks, etc.). It has wider, tougher leaf blades than KBG and tends to grow in dense clumps. You can usually identify it by holding the tip of a leaf blade, grasping it lightly between your thumb and forefinger, and pulling it. If it feels a little like a saw blade in this direction and very smooth in the opposite direction, then it is tall fescue. Tall fescue maintenance is similar to KBG but it is a more robust grass, so maintenance schedules are less critical. Fall maintenance for tall fescue in the Verde Valley is as follows: bare spots can be over seeded September 5- October 1; tall fescue sod is not commonly available; fertilization is the same as KBG; and dethatching/aerification is rarely needed due to a less spreading (bunchgrass) growth form. If dethatching is needed, then it should be done between October 1 and 15. Spring fertilization is also recommended for cool season grasses. Half as much (1/2 pound of actual N per 1,000 square feet) should be applied in both early April and mid-May. Fertilizer should never be applied to cool season lawn in the heat of summer. This is the time of rest for cool season turf. Let's demystify dethatching. Thatch is formed from the dead shoots, roots, rhizomes, and stolons that accumulate just above the soil surface. These plant parts are more resistant to decomposition than grass clippings (leaf clippings rarely contribute to thatch). KBG produces more thatch than other cool season grasses because it spreads by rhizomes (underground shoots). To test your turf for thatch, slice a pie-shaped wedge of grass from your lawn and measure the depth of dead material accumulation. Thatch at depths of ½ inch or less is not detrimental to turf grasses. Thatch depths greater than ½ inch can cause many turf grass problems including: poor rooting; disease problems, insect infestations, dry spots, and proneness to scalping. Dethatching is an injurious process and should only be done at times when the turf is most likely to recover from the treatment. Dethatching equipment (verticutters) can be rented from equipment rental yards. Make sure the equipment is set to treat at a depth to remove the thatch buildup and not the entire grass plant. Aerification is not a substitute for dethatching. Aeration is usually achieved through the use of a core aerator. This machine takes out small plugs if soil to allow better water penetration, reduce compaction, and promote deeper roots. This is most important in situations where traffic is high and water penetration is poor. The resulting cores can be simply broken up and redistributed on the soil surface. Follow these simple guidelines and you'll be less likely to have turf pest and disease problems during the summer months. If you have turf or other gardening questions, call the Master Gardener line in the Cottonwood office at 646-9113 or E-mail us at mgardener@kachina.net and be sure to include your address and phone number. Visit the University of Arizona Turf Research web site at ag.arizona.edu/turf/. |