Will lawn weed control still be effective after the first frost?
Question by Tim D: Will lawn weed control still be effective after the first frost?
I was planning to apply a weed control to our lawn this fall, but we got an early frost, before I had a chance to apply the product. I don’t know that it was a hard, deep frost…but it was definitely below freezing for a few hours. I’m in Iowa. Would it still be worthwhile to apply the weedkiller this fall? It should be above 50 degrees F this weekend. Oh…our primary weed is some type of a clover.
Best answer:
Answer by new england
Tim, almost all of your weeds will die back when it freezes, with the exception of crabgrass. That is an annual that drops its seeds for next year and then dies. No, it’s not a good idea to be spraying weed killer now. Wait until Spring when they will be active. Then apply only what is needed to control them.
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You are correct in thinking that autumn is the best time to apply your weed killer. This is because the perennial weeds will draw the poison into their cells and store it over the winter while they are dormant and it will kill them over the winter. If your weeds have gone dormant for the winter already, it is too late, and the weed killer will just soak through into the ground and become a pollutant and a waste of your time and money. Also, if you wait until spring, you will have to apply it several times and that too will be a waste of time and money and a possible pollutant as your irrigation will wash it through to the groundwater and off of your weeds where you need it most. You may have to wait until next autumn to do it correctly and most effectively. If you have only had a very light frost, there may still be time, but if you’ve had a good hard frost, it’s best to wait. That will preserve your lawn, your pocketbook, the environment, and your time. Good luck!
Hello Tim,
Sugnim’s answer is incorrect.
The best time to apply any herbicide is when the weed pests are at their most vulnerable stage of growth.
In spring weeds are starting to emerge and are barely setting roots.
During the summer months, they are vigorously growing, storing nutrients in preparation to start blooming. Root structure is very developed.
In the fall (autumn), they are mature plants and are using all available nutrients in the soil to set seeds prior to the arrival of winter.
Winter, don’t need to explain much here. Annuals will have died off because of the cold, but their seeds will have already dispersed. Perennial weeds may go dormant after shoring up nutrients in preparation for next years growth spurt in spring.
Again focus at when the weed pest is the most vulnerable. This stage is usually the latter part of spring and beginning of summer. Plant structures are not very well developed at this stage and the weeds are competing with other vegetation for nutrients. They are more likely to absorb the herbicides at this time. Also note, the herbicide label will tell you when is the ideal time to apply it. Clover is a broad-leaf weed with a deep tap root. If you use a herbicide, look for one that specifically controls broad-leaf weeds (selective herbicide). One such example is 2, 4-D. Weed-n-Feed has 2, 4-D mixed in with fertilizer, but you can find 2, 4-D by itself. Products like Round-up are non-selective herbicides that kill any plant they come in contact with.
Weed-n-Feed is typically available in a granular form. You can find 2, 4-D in liquid form, which can be applied via a hose-end sprayer. From past experience 2, 4-D works the best when temperatures are below 80 degrees Fahrenheit and if applied correctly acts a slight pre-emergent. Good luck in your weed control program.