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Warm season grasses often treated like second classBy Richard C. Snell Barton County Extension Agent, agriculture Kansas There is kind of a mentality out there that thinks if you don't have a lush fescue or bluegrass lawn, that you just aren't "uptown." It's almost like Bermuda grass, zoysia grass and buffalo grass get treated like they are second class citizens. Personally, I think our climate is better suited to the warm season grasses. Having said that, I will admit there are some good reasons why we tend to focus more on the cool season grasses. First, we have a good supply of ground water in the south half of Barton County. Thus, a lot of people have sprinkler systems for easy watering. Secondly, cool season grasses stay green longer. They green up quicker in the spring and stay green longer in the fall. Thirdly, if you have many trees around, it is difficult to get warm season grasses to grow in the shade. The pluses for warm season grasses are that they do better in hot weather, take less water, and don't require as much maintenance. We also see more nutrient and disease problems on the cool season lawns. On the other hand if you try to make a grass like buffalo, look like bluegrass, you will usually be disappointed. In that case, it's if you can't beat them join them, because usually you have buffalo grass, because you don't want to do a lot of watering and weed control. Since we usually spend more time on the cool season, today I want to discuss caring for the warm season grasses. Thatch control in warm season lawns In many ways, management of warm-season turfgrasses such as Bermuda grass, buffalo grass and zoysia grass is almost the opposite of cool-season species such as bluegrass and tall fescue. Thatch control is a good example. When thatch is less than 1/2 inch thick, it is not much of a concern; on the contrary, it may provide some protection to the crown (growing point) of the turf grass. However, when thatch exceeds 1/2 inch in thickness, the lawn may start to deteriorate. Thatch is best kept in check by power-raking and/or core-aerating. Because these operations thin the lawn, they should be performed when the lawn is in the best position to recover. For warm-season grasses that time is June through July. Zoysia grass and Bermuda grass are more prone to thatch accumulation than buffalo grass. If thatch is more than 3/4-inch thick, the lawn should be power-raked. Set the blades just deep enough to pull out the thatch. The lawn can be severely damaged by power-raking too deeply. As I rule, I am not a fan of power-raking on most grasses, but I really prefer it for Bermuda grass because it spreads back easily if some grass is pulled out. If thatch is between 1/2- and 3/4-inch thick, core-aeration is a better choice. The soil-moisture level is important to do a good job of core-aerating. It should be neither too wet nor too dry - the soil should crumble fairly easily when worked between your fingers. Go over the lawn enough times so that the aeration holes are about 2 inches apart. Thatch accumulation can also be prevented by avoiding excessive nitrogen applications. Frequent, light watering also encourages thatch. Water only when needed, and attempt to wet the entire root zone of the turf with each irrigation. Finally, where thatch is excessive, control should be viewed as a long-term, integrated process rather than a one-shot cure. One power-raking or core-aeration will seldom solve the problem. Time to fertilize warm season grasses Now is the time to fertilize warm-season lawn grasses such as Bermuda grass, buffalo grass, and zoysia grass. These species all thrive in the warmer weather of summer; accordingly, that is the time they respond best to fertilization. The nutrient of greatest importance is nitrogen (N), and these three species need it in varying amounts. Bermuda grass requires the most nitrogen, about 4 pounds per 1,000 square feet, during the season. Apply this as four spaced applications (about 4 weeks apart) of 1 pound N per 1,000 square feet. The nitrogen can come from either a fast or slow-release source. Plan to make your last application no later than Aug. 15. This helps ensure the Bermuda is not over-stimulated and therefore, less susceptible to winter kill. Zoysia grass grows more slowly than Bermuda grass and is also prone to getting "thatchy." Consequently, it does not need as much nitrogen. In fact, too much is worse than too little. Two pounds N per 1,000 square feet during the season is sufficient. Apply 1 pound now and another around mid-July. Slow-release N is preferable but fast-release is acceptable. Buffalo grass requires the least nitrogen of all lawn species commonly grown in Kansas. One pound of N per 1,000 square feet is generally enough for the entire season. This application should be made now. For a little darker color, fertilize it as described for zoysia grass in the previous paragraph, but do not apply more than a total of 2 pounds N per 1000 square feet in one season. Buffalo grass tends to get weedy when given too much nitrogen. As with zoysia, slow-release nitrogen is preferable but fast-release is also OK. As for all turf grasses, phosphorus and potassium are best applied according to soil test results, because many soils already have adequate amounts of these nutrients for turf grass growth. Iron may occasionally be needed, especially where soil pH's are above 7.0 to 7.5, like they are in much of Barton County.
Date: 7/10/08
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