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Why are some weeds harder to kill in the summer?

During the summer months it is not unusual to see an influx of weeds. This is because in the summertime not only does our grass start to go dormant to protect itself, but so do the weeds. When temperatures rise, weeds grow more slowly and develop thicker cuticles which reduces movement of herbicides through their root system; making them harder to control. When the herbicides are not working as well you will not see as many die off and it will appear as if there are more weeds present. 

Common weeds in the summer
In the summer you will see certain weeds are more stubborn to kill than others. Such as; wild violet, creeping charlie, broadleaf plantain, and deadnettle etc. Wild violet is a known harder to eradicate weed. Their seeds can last up to 6 weeks in the lawn and reproduce multiple times in those weeks. Some weeds will die off in the summer due to the heat (winter annuals) such as; common chickweed, shepherd’s purse, yellow rocket and dandelions etc. Some weeds thrive and can withstand the summer heat which makes it harder to kill them even with the correct products. 


“Some weeds will die off in the summer due to the heat”

Products
In the spring and fall months we will use a product called T-zone (Triclopyr) to kill off weeds. This is a very effective weed control as it is a selective weed control meaning it kills a broad-spectrum of weeds. It is a highly concentrated product therefore we can not use it in the summer. It can not be used in extreme heat or it will burn the grass. In the summer we switch to Momentum weed control. Momentum FX2 contains the active ingredients Fluroxypyr, Trioclopyr and TIPA -2, 4-D. This is also a selective weed control of perennial and broadleaf weeds. This does make it more difficult to kill the weeds in the summer. However it will help to control and maintain them. It will help slow the reproduction of seeds and make it harder for them to spread.

 

“These are grassy-weeds that appear in the summer and require a selective herbicide to eradication”

Other common misdiagnosed weeds in the summer
When you are looking at your lawn you may notice weeds that look similar to grass such as crabgrass, barn grass, annua poa and nutsedge. These are grassy-weeds that appear in the summer and require a selective herbicide to eradication. For nutsedge it is a short lived plant and dies off in the winter we will use Sedgehammer to kill it off. With crabgrass, we will use a selective product called Quinway to kill this plant, we do recommend an aeration and seeding in the fall following this treatment. The reason behind this is because there is no grass under the crabgrass plant and it will cause bare spots in the lawn and this will also help to prevent future crabgrass plants. Unfortunately with annua poa and barn grass, there is no selective herbicide treatment available.  The only option is to use a non selective herbicide like RoundUp that will kill everything.

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