Five Things You Need to Know About Pre-Emergent Weed Control – Warm Season Lawns
What is the purpose of Pre-Emergent Weed Control?
Pre-emergent weed control is designed to prevent a variety of weeds before they appear. This is achieved by applying a protective layer of pre-emergent herbicide to your lawn, preventing the weed seeds from penetrating this protective layer. Pre-emergent does not know the difference between a weed seed and a desirable seed like Bermudagrass or ZoysiagrassTall. Once applied it will inhibit all seed-based germination!
When Should I Apply Pre-Emergent Weed Control?
Throughout areas of the southern and southeastern United States, it is important to apply pre-emergent weed control at the right time of year. If the herbicide is not applied prior to germination, it is not effective. This means the protective barrier must be applied before weed seeds can germinate.
For warm-season lawns, we apply pre-emergent two times a season; late Winter/early Spring and early Fall.
In late Winter/early Spring, we like to apply the pre-emergent before forsythia shrubs reach full bloom. Their blooming signals soil temperatures are reaching 55°F, which is when summer annual weeds begin to germinate. It can be weather-dependent, but typically the best time to apply a pre-emergent weed control treatment is during February through early April.
After April, you will be less likely to see good results from a pre-emergent weed treatment, because weeds have begun to germinate. The exception here, of course, would be if it had been a particularly cold season, leaving seeds dormant longer.
In early Fall, we aim to apply pre-emergent before the soil temperature drops below 65°F; mid-September – mid-October. Once again, if we experience a longer summer, this application window extends.
How Long Does Pre-Emergent Weed Control Last?
Every product is a bit different. Typically, you can expect one treatment to last ~ 5 months.
It is also important to select a good product. If you’re planning to try and treat your lawn yourself, always be sure to read the labels, so you understand how long the manufacturer suggests their product lasts. A professional lawn care technician will be able to answer this question for you.
What Types of Weeds Does Pre-Emergent Weed Control Treat?
Pre-emergent weed control is effective prior to germination on most all seed based annual weed varieties. This includes common weeds like crabgrass, and poa annua (annual bluegrass). A weed that is a perennial (grown from a vegetive structure like a root or bulb), pre-emergent herbicides will not inhibit their growth.
Can Pre-Emergent Weed Control Harm My Lawn?
Pre-emergent weed control is not harmful to your lawn. If you plan to plant new grass seed to your lawn, treatment should not be applied to those areas prior to germination.
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