Critical time for North Texas lawns has arrived. Watch out for these stumbling spots.

We’re at a time in North Texas lawn care when our responsibilities take some 90-degree turns. People who have been down this path before know the possible stumbling spots, but it never hurts to mention them again. And if you’re a newcomer, you need to be put on alert.

For instance, it’s time for the second application of pre-emergent weed control granules to prevent germination of crabgrass and grassburs. These are products like Dimension, Balan or Weed-EX with Halts. They’re applied before you can see the actual weeds germinated and growing.

Pre-emergent herbicides attack the seeds and very young seedlings and prevent them from developing. They have no impact on plants that are already existing, which is why, if you didn’t make the first application back in the middle of March, this second treatment won’t be of any value.

The granules can be applied to any type of turf that has been established for at least one growing season. Apply the granules immediately and water the lawn after you spread them to get them onto the soil surface.

It’s time for your lawn’s second feeding. Most test results from the soil testing laboratory at Texas A&M suggest that we use a high-quality, all-nitrogen fertilizer for lawns in the Blackland Prairie clays here in the Metroplex. Our soil accumulates phosphorus (middle number of the three-number fertilizer analysis) to the point of its building up to levels that are detrimental to healthy plant growth.

That buildup of phosphorus is the reason for the lab’s recommendation of an all-nitrogen product, and the thing that sets them apart from lower-quality fertilizers will be if they have 30 to 40% of that nitrogen in encapsulated or coated, timed-release form. That’s what you want for sustained feeding.

Taking that one step further, there is a disease that has become increasingly common in St. Augustine and zoysia lawns in the summer. It’s recognized by the angular, grayish-brown spots it puts along the midribs of the leaf blades. That’s what earns it the name of “gray leaf spot.” It shows up in hot weather of late June, July and August. Curiously, it is much more noticeable in lawns that have been fed recently with nitrogen.

So, here we have an impasse. Turfgrass only needs nitrogen to maintain healthy, green growth, but that same nitrogen promotes a fungal leaf spot in the prime part of the growing season.

What’s a gardener to do? You simply fertilize around the heat. Typically, we have over-fed our St. Augustine lawns. The logical answer is to fertilize it in mid-April, mid-June (now) and not again until early September. That works well with zoysia turf as well, and it will help you avoid the issues with gray leaf spot in the process. Any that does show up can be addressed with the fungicide Azoxystrobin.

Bermudagrass is much less affected by this disease. It also benefits from more frequent feedings, so put it on a program of feeding every two months, mid-April through mid-October. Use the same all-nitrogen fertilizer.

If you have weeds popping up in your lawn you can address them at this time. I have some specific suggestions.

For non-grassy weeds in St. Augustine, including dichondra, clover, dollarweed and others, spot treat with a broadleafed weedkiller. The 2,4-D products will burn St. Augustine, so spot treat the weeds, keeping the spray off the St. Augustine as best you can. Spray late in the day after the sun is off the turf.

Nutsedge (“nutgrass”) can be eliminated in any type of lawn using the original version of Image (there are subsequent products under that brand name now for other purposes) and Sedgehammer. These herbicides work more slowly than you may be expecting, so be patient. Read and follow label directions carefully for best results.

Dallisgrass is a difficult weed to eliminate since you’re trying to control one grass within another grass. We used to have MSMA to do that job in bermuda turf, but it’s gone now for use by consumers, so my suggestion becomes the same for all types of grass. Cut the bottom out of a 1-gallon milk jug and remove the jug’s top. Mix a spray of the original Roundup (glyphosate as the only active ingredient). Place the jug down over the dallisgrass clump. Insert your spray nozzle into the jug and spray the dallisgrass. Once you have finishing coating its leaves and stopped spraying, lift up the jug and allow the spray to dry. The dallisgrass and all other vegetation within the confines of the jug will be killed, but the soil will not be contaminated in any way.

If you are planning on planting new sod, seed or plugs this season, get that job done as soon as you can. As the soil dries out and temperatures continue to rise, it will be more and more work to get new grass established. Prepare a good planting bed 3 inches deep. Rake to a smooth grade away from your house and plant the new grass. Water it for 5 to 10 minutes morning and night to be sure that its tiny new roots don’t dry out. After a couple of weeks you can begin to wean it to a more normal watering schedule.

You can hear Neil Sperry on KLIF 570AM on Saturday afternoons 1-3 p.m. and on WBAP 820AM Sunday mornings 8-10 a.m. Join him at www.neilsperry.com and follow him on Facebook.