Dr. Grow: Getting rid of pesky weeds

Oxalis

Prostrate spurge

In my last column, I told you how to rid your lawn of those hard-to-control grassy weeds. I thought that this week I should tell you how to get rid of those pesky, hard-to-control broadleaf weeds that can easily overtake your lawn.

I told my wife about the topic of this week's column. She told me to write about something else. I suppose she thinks weeds are boring and she didn't want me to lose the interest of you, the reader. As all good hubbies do, I listened to her. I really thought about what she said, but there seems to be so much interest (or concern, or disgust) in lawn weeds. I'm not sure what this interest stems from, but I do know that when I was in the lawn care business, I received more calls about weeds than anything else. So, sorry Honey, I'm writing about lawn weeds again.

As in all cases of pest control, it is best to identify the weed first and then determine how to control it. In this area, the most common hard-to-control summer weeds are violets, prostrate spurge, oxalis, lespedeza, and clover.

Everyone knows what clover is, so there is no need to describe it. Oxalis is similar to clover, but the lighter green leaves are smaller. The white flowers of clover contrast with the yellow flowers of oxalis. Clover forms patches of weeds, while oxalis is found as individual plants.

Lespedeza is also similar to clover. The plant grows close to the ground and the stems are somewhat woody. The flower is usually pink shading to lavender. This weed is usually found in patches, as is clover.

Wild violets are often planted in flower gardens, but when they escape they become hard to control weeds. Violets have heart shaped leaves and the flowers are lavender in color. Even though the plant grows in clumps, the plants can spread easily from root stalks.

Prostrate spurge is usually found in weak lawns that have been treated with a crabgrass pre-emergent. The absence of crab grass eliminates competition for spurge and it can then grow profusely. This ground-hugging plant develops from one main stem and branches out in a star pattern. The small oval leaves may have a pink tinge to them.

Broad-leaved weeds usually can be controlled by selective herbicides. The selective herbicide will kill the broad-leaved weeds and not harm the lawn grasses. In fact two different herbicides, trimec and triclopyr will control essentially all broad-leaved weeds that you find in your lawn.

The perennials -- oxalis, clover, and lespedeza -- can be controlled with trimec. Make two or three applications at one week intervals. Spray solutions tend to bead up on the leaves instead of spreading out over the entire leaf. The herbicide is introduced to the plant through the leaves. Because the spray solution beads up, it is harder to get a herbicide into the leaf. Consequently more than one application is needed for control.

Prostrate spurge is an annual that reseeds itself several times during the summer months. Again trimec will control this pesky weed but several applications will need to be made in order to control all of the generations that are produced during a season.

Wild violets are the only weeds in our discussion that need to be controlled with triclopyr. Even the use of this herbicide will take two or three applications for control.

The herbicides trimec and triclopyr can be found at your local garden center under various trade names. The clerk at a reputable garden center can help you find these common weed killers.

Oh, by the way Honey, this is the last article on weeds for a while.

Paul Schnare of Cape girardeau has been in the lawn and garden business for more than 20 years. He's an adjunct professor in horticulture at Southeast Missouri State University.