There are several critical lawn care tasks you really must perform now if you hope to have respectable turf this fall and coming out of the winter ahead. C-R-I-T-I-C-A-L!
Fall pre-emergent application time: August 25-September 5
Those are dates I’ve come up with myself based on almost 50 years of fine-tuning here in the DFW area. Every year I’d give dates into September, and folks would report back that they still had cool-season weeds. I finally settled on the last week of August through the first week of September and the problems seemed to drop to a minimum.
So let me explain. We’re talking about weeds you cannot see at this point. They’re weeds that show up from late fall and especially into early and mid-spring. Grassy weeds like annual bluegrass (Poa annua), rescuegrass and ryegrass can be prevented before they ever germinate (or “emerge”) by use of Dimension, Halts or Balan granules during the time period I noted.
Similarly, broadleafed annuals like clover, dandelions, henbit and chickweed can be prevented by application of Gallery granules in that same window of time. The two types of granules cannot be mixed in your fertilizer spreader’s hopper, so plan on making two passes over your lawn, then watering them onto the surface of the soil with moderate irrigation.
It’s worth noting that you get no second chance with the grassy weeds. Once they sprout and start growing you’re going to have them until they go to seed in April. However, you can apply broadleafed weedkiller sprays to kill the non-grassy weeds later this fall or in early spring, so you do get a second chance with them.
Additional notes: If you have new turf that was started this year you should not apply pre-emergent weedkillers until it has been through its first winter. These products are safe on any type of lawngrass, and they can be used around trees and shrubs. If you have a lawn care service doing work for you, they have access to other products that may have different application deadlines.
Last call to apply control for nutsedge
Some call it “nutgrass,” but you can distinguish sedges from true grasses by rolling their stems between your index finger and thumb. Sedges have triangular stems. All true grasses have round stems.
Nutsedge is a comparatively attractive weed with glossy, dark green leaves that somewhat resemble mondograss (monkeygrass). The plants spread aggressively as they overtake flowerbeds and turf, even penetrating asphalt in the process.
Digging is futile as a means of controlling it. You can apply a layer of weed-blocking fabric and leave the area covered for a couple of years and probably starve it out, or you can use either Sedgehammer or the original Image herbicide to eliminate it. Both weedkillers are fairly effective, but your time is running out quickly for this growing season. Image, for example, requires two treatments 30 days apart, with both falling between mid-May and mid-September. You can see that you’re already at the tail end of that treatment time.
New lawns should really be started now
People frequently ask, “How late can I start my new seed?” Or, “How late can I plant my new sod?” In some cases they’re just waiting for fall’s cooler weather because starting new turf isn’t easy. In other cases they’re moving or taking possession of a new home and need to know their absolute deadlines.
Bermuda from seed needs to be started as soon as possible to give it time to become well rooted before the ground starts to turn cool. The same goes for St. Augustine sod. September 1 is probably the cut-off for each of those. Zoysia sod can go in a couple of weeks later, and bermuda can go through September if need be. There are landscape contractors who actually plant bermuda sod clear through the winter, but you really have to be attentive to keeping it watered. That’s not always easy because you can’t tell if it’s dry when all the blades have turned brown from the cold.
Still plenty of chinch bugs and gray leaf spot
Keep an eye out for these two ongoing St. Augustine issues of summer.
Chinch bugs: These will be in the hottest, sunniest parts of your yard. The grass will appear to be dry, but it won’t respond to irrigation. That’s when you want to look closely at the surface of the soil, even if it means getting down on all fours.
The culprits are probably chinch bugs. They’re BB-sized black insects with irregular white diamonds on their wings. They and their immature red nymphs will be moving about freely on the surface of the soil in areas where the grass is impacted, but not where it has already turned completely brown.
If you see them moving actively, treat immediately with one of the labeled chinch bug insecticides. Without that treatment chinch bugs can kill your turf within just a few days.
Gray leaf spot: This is the other hot-weather nemesis of St. Augustine. Your lawn will take on washes of yellowish-green as if it needed to be fertilized. But feeding it nitrogen only makes the problem worse. Check the leaf blades closely for gray/brown, diamond-shaped spots on the midribs and runners. If you see those gray leaf spot fungal lesions, apply a fungicide labeled for leaf spot on turf, but even more importantly, discontinue all feedings with nitrogen fertilizer each year between mid-June and early September. Nitrogen seems to exacerbate the issue with this disease.