Originally published on September 23, 2020.
With our fingers crossed and the hope of cooler weather, we need to think about how to it will affect the growth of warm-season grasses like St. Augustine, centipede, Bermuda, and zoysia. Typically, the cooler weather means that these grasses will begin to slow down. With this slowdown in growth, it is not a good idea to do anything that would disrupt or damage the turf such as filling, aerating, or dethatching. Even though we should not have to mow as often, it is still important to mow regularly to maintain proper height and make sure that mower blades are still sharp.
to LSU AgCenter Specialists, most warm-season grasses will be completely or
partially dormant by mid- to late November or December. The only exception may
be with St. Augustine, which may not go completely dormant during mild South
Louisiana winters. This dormant period is how the turf in your yard can survive
the potential freezes during the winter months.
The LSU AgCenter does not recommend applying fertilizers high in nitrogen (the first of the three numbers on the bag) this late in the summer as it will stimulate fall growth. This stimulated growth this late in the summer makes the grass more susceptible to cold injury this winter by not allowing it to go dormant and in the case of St. Augustine grass, attack from the fungus disease called brown or large patch during the mild fall months.
This time of year, we begin to see and hear about a good time to winterize your lawn. According to Ron Strahan, LSU AgCenter Turf Specialist, winterize is a term, when used with warm-season grass lawn care, is simply stated as slow down growth, and increasing the levels of nutrient potassium (the third number on the bag), which is an attempt to toughen plant tissues for the winter freezes. Be careful with winterizers that contain high levels of nitrogen. The first number in the analysis of these fertilizers, which is the percentage of nitrogen, should be zero or very small. The third number, which is the percentage of potassium or potash in the fertilizer, should be the highest, as in 0-0-60, for instance. We recommend you do not purchase winterizers with substantial amounts of nitrogen.
If you are having a problem with late-summer broadleaf weeds you can spray lawn weed killers now. There are many formulations available that kill a wide range of weeds with a single product. As always check to label to make sure it is suitable for the type of grass you have in your lawn. Just remember, since it is too late to fertilize, stay away from using weed-and-feed herbicide and fertilizer this late in the summer.
It is also the time of year to begin to think about preventative weed control for cool-season annuals like burweed (sticker-grass), chickweed, henbit, and annual bluegrass. These preemergence herbicides kill weeds as they germinate and before they emerge from the ground. Timely applications of these herbicides are critical for success and should be applied by early October. Preemergent herbicides prevent weed growth for several months and usually last through the spring. There are several preemergence herbicides available to homeowners in easy to spread granules and are less likely to damage your lawn if used as directed. LSU AgCenter recommends products like Greenlight Crabgrass Preventer, Hi-Yield Dimension, Scott’s Halt, and Greenlight Portrait. However, if you plan to overseed your lawn with rye, do not use these preemergent herbicides.
Insects and disease problems also occur later in the year. A common disease that is seen, especially in St. Augustine, during cooler, wetter months is brown patch (see photo bottom left). The areas of grass scan have yellowish or orange cast that turns tan or brown color. Spread can be rapid and your grass will recover in the spring. If you decide to treat, fungicides labeled to control lawn diseases are available.
Another pest that can be active if the hot, dry weather lingers into the later months of the year, is the chinch bug. These ant-sized insects feed by sucking the sap from the grass, causing it to dry out and die. To spot this damage look closely at the blades of grass in the affected dead areas and see if they look rolled up lengthwise (see photo bottom right). Since chinch bugs kill the grass, we recommend prompt treatment to minimize damage. There are a variety of lawn insecticides to control chinch bugs and are available wherever garden pesticides are sold.
As the weather begins to cool, and the mowing of our lawns decreases, homeowners will enjoy a little lawncare relief. However, don’t let this keep you from making sure your lawn is ready and protected from the winter months ahead. A little time in the lawn in the fall can payoff for a healthy, green lawn next Spring.
For more information on fall lawncare or other related topics, visit the LSU AgCenter website or call Mark Carriere, Pointe Coupee Parish County Agent, at the Pointe Coupee Parish Extension Office at (225) 638-5533 or via email at firstname.lastname@example.org.