Too many weeds are sign of poor lawn care

By Steven Olson
North Forty News

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The grass turned green, the trees leafed out, the vegetables in the garden grew thick and the weeds came back.

Every year weeds manage to return to the lawn and the garden and every year people stoop or spend time on their knees and pull or spray and try to eradicate. And rarely does it work because they either take the wrong approach or the weeds are so tenacious that they may disappear one year but come back the next.

Here are the top five weeds in local lawns.

Dandelions

"This is the most common weed in lawn care we get calls on," said Tony Koski, Colorado State University Extension turfgrass specialist. "It's everywhere. We always get calls about it. Everyone wants that nice, green lawn, and dandelions spoil the look of it."

Koski said dandelions in a yard are incredibly stubborn and a sign of an unhealthy lawn. Rather than concentrating on the weeds, Koski said, homeowners have it backwards. They need to concentrate on the grass.

"If you are getting dandelions, or clover or other kinds of weeds," Koski said, "your lawn is not healthy. It hasn't been fertilized right. It's not being watered right."

A healthy lawn, he added, crowds out weeds.

Koski recommended homeowners mow twice a week and set their mowers so they leave behind a blade that is around 2.5 inches tall. Cutting shorter, or scalping the lawn, causes the grass to throw energy into growing individual blades rather than roots that choke out weeds.

People should fertilize new lawns four times a year and mature ones twice a year. They should water their lawns every week, and really "hit it" every two weeks. "Most people underwater their lawns, especially around this time of year," Koski said, adding that watering every day is a mistake because weeds really like it.

Bindweed

This is probably the number two weed problem. Alison Stoven, the Larimer County Horticultural Extension Agent, gets calls on it all the time. Bindweed, also known as dodder, is a low-growing, vining plant that looks like miniature morning glory. It's incredibly durable.

"I swear it can grow in concrete," said Stoven.

It's more a problem for gardeners because it will grow on the edges of gardens or the edges of lawns. Because the seeds can live for 30 years, said Stoven, even a careful gardener can inherit the problem from the previous owner.

People assume the popular herbicide, Roundup, will kill the plant just like it kills every other plant it touches. Not so. "It will kill the leaves," Stoven cautioned, "but it won't kill the roots." New bindweed plants can spring from root fragments.

That's why a new systemic herbicide that kills the entire plant is getting attention. Quinchlorac can be found in a product called Ortho Weed B Gone Max Plus Crabgrass Control.

Stoven advised people to use Quinchlorac on lawns only, not gardens, because it is incredibly toxic to the plant family that includes tomato and eggplant. Stoven normally does not cite one product over others in order to avoid calls of favoritism.

Crabgrass

Crabgrass starts out as little darker-green patches of grass on a lawn. That's the time to take care of it, said Koski. "It's much easier to kill then," he said.

Crabgrass is unsightly. When pulled out by its shallow roots, it leaves behind a hole in the grass.

Crabgrass might as well be the poster child for Koski's main bit of advice when dealing with weed problems: Know what you're dealing with.

Some people see weeds and rush down to the garden center to buy all kinds of chemicals to spread on the lawn. "You need to know what you're dealing with before you try and kill it," Koski advised.

In the case of crabgrass, the best thing to do is put down a crabgrass preventer in the spring, he said.

Mallow

Mallow is a small plant with wrinkly green leaves roughly in the shape of a maple leaf. If left to grow, mallow forms small pinkish-white flowers. It has very long roots and grows in bare spots where grass is not doing well or in spots beneath vining plants in the garden where it's hidden from sight. It can come back again and again.

Mallow looks like a weed. The best bets for people here are products like Weedone, Turflon or Trimec, Stoven said. Each product is a combination of 2,4-D with another chemical.

Clover

Some people are so defensive of their green stretch of grass that they even regard a patch of white clover--that stuff that can grow the famous four-leaved clover and that bunnies like to eat--as a weed. For those who share the sentiment, Koski recommends a chemical called MCPP for weed control. It is like 2,4-D.

For more information about establishing and maintaining a healthy lawn, see Extension Fact Sheet 7.202 on Lawn Care at www.ext.colostate.edu/PUBS/GARDEN/07202.html.