Why You Still Have Weeds After Pre-Emergent
You had pre-emergent applied. It’s July, and your lawn is crawling with crabgrass anyway. What happened? Almost every time, it’s one of three things, and all three are preventable.
Reason 1: Applied too late.
This is the #1 cause. Pre-emergent works by forming a barrier that stops seeds from germinating, it does nothing to weeds that have already emerged. In North Texas, weed seeds start germinating when 4-inch soil temps hit 55°F, which can happen as early as the first week of February. If your applicator came out in late March, the barrier went down after germination had already started.
Reason 2: Applied at too low a rate.
Pre-emergent needs to be applied at the full labeled rate to create a dense enough barrier. Some low-cost lawn services cut the rate to save on product. The lawn looks treated. The weeds still come through because the chemical barrier is too thin to stop them all.
A professional applicator uses calibrated equipment and the full labeled rate. It’s the difference between a preventive treatment and a coat of spray.
Reason 3: Only applied once per year.
A single spring application misses half the weed calendar. Winter weeds germinate in fall, meaning a spring-only program leaves the door open for Poa annua, henbit, and chickweed to establish from October through March. By the time spring pre-emergent goes down, those weeds are already adult plants, pre-emergent can’t touch them.
A two-pass program (spring + fall) is the standard for any lawn that’s expected to stay clean year-round.
“If pre-emergent was a magic spell, it would be cheap. It’s cheap because it’s science, and science only works when you follow the protocol.”
— Chris Rather, CGCS
See how Rather Green times pre-emergent →
Or call Chris directly at 972-649-9912 for a free lawn evaluation.
