Brock: Late summer brings new protocol for grass

Published 12:00 am Wednesday, August 7, 2019

August’s heat is at least as bad as July’s and we’re more tired of it by now. But I’m not complaining. I actually see a decrease in calls and emails from home horticulturists in late summer. I think it’s because no one is interested in going outside and messing with his or her plants (or that most plants, at least annuals, are dead by now from heat, neglect, etc.). And as Stephen King taught us in Pet Sematary, “Sometimes dead’s better.”

But how about that grass? Just about all our perennial grass species are from equatorial Africa and Asia. They relish the heat and have benefitted (in most cases) from the ever-present “scattered showers” in Louisiana afternoons. So like it or not, we’ll all be mowing for a while now.

While we can do a number of things to improve our lawns, the easiest and often most effective is to adjust mower blade height. Usually this means raising it since most homeowners tend to cut the grass too short. Conventional thinking is that if we cut it short enough we won’t have to mow as often. (This is technically true, as you may manage to kill it entirely.) But frequency is usually once a week anyway and this won’t change.

Bermudagrass is one it’s suggested we mow down to an inch or so, along with some varieties of zoysia. But most of us have St. Augustine, centipede, or a combination of grasses. These are better mowed no lower than two or three inches. Especially if you have shade in your yard, taller (just over three inches) will result in a healthier lawn. Those leaf blades need all their surface area to photosynthesize (make food.)

Taller grass usually looks better too. What’s attractive to the human eye on a flat plane (your yard in this case) is uniformity. Despite the backlash I commonly get on this, taller grass looks great as long as it’s all the same height; i.e. mowed regularly. Is your lawn perfectly professionally graded, or does it have bumps and dips? Those imperfections are highlighted when grass is mowed short. And it commonly results in brown spots where the mower blades scraped too close to the ground. In areas of thinner turf, the tall blades help make the grass look fuller too. (Guys, don’t try this on your hair. The combover is passé.)

Properly mowed grass is more competitive against weeds. Some will be shaded out. Others will be less noticeable. For those that require herbicide treatment, be careful in hot weather. Selective herbicides kill broadleaf weeds but won’t kill grass. BUT most will yellow your grass in severe heat. Spot treatments are more appropriate than broad application. And err on the lower rate the label suggests. Anything containing 2,4-D is especially dangerous this time of year. Your best bet is MSM Turf, which causes very little collateral damage in hot weather.

If you want your grass to grow faster and fuller (unlikely) OR if you have problem areas that could use some growing over, August is the last month we suggest applying nitrogen. Anything later risks large patch going into cooler weather, or possibly cold damage later. You can apply a pound of actual nitrogen (not a pound of fertilizer) per thousand square feet.

If you want to know more about gardening, landscaping, or anything else horticultural, contact the St. John, St. James, & St. Charles Parishes County Agent André Brock at Also, the LSU Ag Center’s website can be accessed at with lots of user-friendly information, including this article.