Dandelion controls best late in growing season

November is a good month to get rid of those pompom-headed dandelions.

KSU News Service

MANHATTAN --- If you want to insult the dandelions that cheerfully invade lawn and garden, spray them in spring. But if you want to get rid of dandelions, try the fall.

Dandelions are like Kansans' favorite lawn turfs: tall fescue and Kentucky bluegrass. All are cool-season perennials, which means they grow best every spring and fall.

In spring, however, they're devoting most of their energies to sprouting and producing leaves and flowers. In fall, they're focusing on roots and preparing for winter.

"So, you treat dandelions in fall for the same reason you fertilize fescue lawns then-the applications will affect the plants' very foundations. In fact, some combination products are available that will accomplish both jobs at the same time," said Kansas State University horticulturist Steve Keeley. "Fall is the time to use these fertilizer-broadleaf herbicide combos. Using them in the spring just doesn't give the same results."

Early-season dandelion controls, for example, usually kill leaves and flowers. But the roots may get too little herbicide to kill the entire plant. So, the dandelion often will sprout again, he explained.

Similarly, spring-fertilized fescue may green up well and develop lush leaf growth. But that growth can outstrip the roots' ability to support the lawn through Kansas' hot summers.

In most years, Kansans can successfully use broadleaf weed herbicides through the end of October, said Keeley, who is the turfgrass specialist for K-State Research and Extension. They can use products that combine a broadleaf weed herbicide and lawn fertilizer in either September or November.

"If you don't have a problem with winter annual weeds, such as henbit and chickweed, apply the combined product in September," he recommended. "But if you're concerned about dandelions and winter annuals, apply the combination in November. By then, many of the winter annuals will have germinated and be susceptible to herbicides."

Kansans must apply combination products when temperatures are at least 55 degrees F, Keeley said. They also must apply herbicide

fertilizer mixes when grass is wet enough that the granular herbicide will stick to foliage.

"Apply after a rain or after you've watered your lawn," he suggested. "Or, get up early and apply the combination while dew is still covering the grass."

The combination products are convenient to use and will do a good job of controlling broadleaf weeds, Keeley said. Still the most effective dandelion controls probably result with a liquid broadleaf weed herbicide, sprayed under these conditions:

- The weeds are actively growing.

- Soil moisture is plentiful (never droughty).

- Air temperatures are between 60 and 75 degrees F (never above 80 degrees).

- Wind speeds are below 5 mph.

- The lawn will not receive moisture through rain or irrigation for at least 24 hours.

- The lawn will not be mowed for several days before or after the application.

- The person doing the applying reads and follows herbicide label instructions carefully.

"The last factor can be vital," the horticulturist added. "Using the wrong product for your type of grass can cause damage."

The most common post-emergence controls for broadleaf lawn weeds contain (1) 2,4-D; (2) MCPP; (3) dicamba; or (4) some combination of these three, Keeley said.

"In the long run, of course, the best way to discourage weeds will always be to have healthy, dense turf," he said. "With proper variety selection, watering, mowing, and fertilizing, grass stands will soon become thick. And that, in turn, will reduce the need to apply herbicides."

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