Fall Pre-Emergent Timing for Weed Control in McKinney

How to Stop Winter Weeds in Collin County

Does your North Texas lawn get filled with weeds every February? You need to stop it back in September.

That’s why it’s called pre-emergent, it’s weed control before the weeds actually emerge. By the time you can see the weeds, it’s too late.

Common winter weeds in McKinney and the surrounding area include Poa Annua (annual bluegrass), henbit, and chickweed.

These winter weeds start germinating in the fall, and that’s the time to control them. However, it’s not as simple as following the calendar.

Pre-emergent Timing

Proper timing of pre-emergent is based on soil temperatures, not the calendar. If your lawn care company sticks to a fixed calendar schedule of when they apply pre-emergent, it may not be effective.

Winter weeds like Poa start germinating when the soil temperature drops into the low 70’s for several days in a row. The soil temperature is taken about 2-3 inches below the surface.

Here in North Texas, that can be mid September, late September, or even Early October. Late September is typical, but the weather here is unpredictable. That’s why soil temperature is more reliable than the date.

In fact, horticulturists usually say that soil temperature is the important factor for germinating seeds, whether it’s weeds or vegetables (https://hort.extension.wisc.edu/articles/when-is-the-right-time-to-plant-vegetable-seeds-check-soil-temperature/).

Of course, the timing also depends on the type of weed you’re trying to control. Henbit and chickweed can germinate until the soil temperature is in the 50’s. So to cover all three of these common weeds, it may be helpful to have a second application.

Why is Timing for Pre-emergent So Important?

The way a pre-emergent control weeds is by preventing the germinating seedling from putting down roots. Once it takes root or you can see the weeds, the pre-emergent will not kill the weeds.

So applying it too late is useless. Applying it too early is also not helpful. The chemicals will break down and not be effective when needed.

You also need to coordinate with any other yard work being done. For example, don’t do core aeration soon after pre-emergent application, as this will destroy the pre-emergent barrier and allow seeds to bypass it.

If you one lawn care company taking care of your regular maintenance and landscaping, and someone different for weed control, just make sure they are aware of what the other is doing.