When to apply pre-emergent in Prescott? Before rain.
Right before it rains. But Prescott-area rain is hard to predict, so the length of residual matters more than the month.
The short answer
Apply pre-emergent right before it rains. Since rain is unpredictable, a long-residual product on a year-round schedule beats picking one month.
That is how Guardian Landscape approaches it: pre-emergent at month 1 and month 7 of a six-visit year. See the weed control plan.
Pre-emergent only works once it is in the soil
Pre-emergent stops seeds from germinating, but only if it gets into the soil.
It does not kill weeds already growing. On a gravel or rock yard, liquid pre-emergent sprayed on top sits on the rocks until rain or snow washes it down to the soil. That wait is the whole timing problem.
Why rain decides the timing
Prescott is high desert, so rain and snow are sparse and erratic.
July and August are the wettest months, thanks to the summer monsoon. But the monsoon does not show up the same way every year. In July and August of 2020, the area got about 2.08 inches of rain, against a typical 5.5. A yard treated only in a month that turned out dry may have gone without rain for a long time.
Residual: how long it waits for rain
Residual is how long a product stays active after it is applied.
The pre-emergent product and rate Guardian Landscape uses gives about 8 months of residual. A long residual gives the rain more time to arrive. In a wet stretch residual matters less. In a dry stretch it is the difference between pre-emergent staying on top of the rocks and getting into the soil.
What pre-emergent controls
Pre-emergent controls broadleaf weed seeds, which covers the most common weeds.
Puncturevine, also called goathead, is an introduced invasive annual in Yavapai County and a common local broadleaf weed. It is listed among local weeds by the University of Arizona Cooperative Extension in Yavapai County. Very invasive weeds may need more than pre-emergent alone.
If you already see weeds
Pre-emergent will not remove them. That is the job of post-emergent.
Post-emergent spray knocks out weeds that push through. That is why our plan has four post-emergent visits between the two pre-emergent visits. See how the six visits fit together.
Get your yearly price.
Tell us your name and number, then your yard size. Guardian Landscape calls or texts you with your exact yearly price.
Call (928) 396-1577