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Johnson County

Research-based Information You Can Trust — Localized for your needs

Johnson County
11811 S. Sunset Drive
Suite 1500
Olathe, KS 66061

(913) 715-7000
(913) 715-7005 fax
jo@listserv.ksu.edu

Map to our office

Lawn Weed Control

Return to Weed Agent Articles

Dendelion weed in lawn

Maintaining a beautiful lawn in the Kansas City area is a challenge. It seems that year-in and year-out some funky weather pattern creates a problem. It is either too wet or dry, hot or cold, which creates stress on area lawns. When turf becomes stressed the grass plants decline, which leads to many problems, one of them being weeds.

The result is a thin lawn, and whenever a lawn thins and reveals the soil then weeds pops up. It is just not one weed but a combination of crabgrass, dandelions, henbit, chickweed, spurge, clover, wild violets, nutgrass, and the list can go on and on.

Weed control is also more difficult and frustrating because there are grassy and broadleaf weeds, cool season and warm season weeds, and those that have annual and perennial life cycles. As a result of these different classifications, there is just not one application or timing that rids the lawn of weeds.

Know your weed before you treat

So what are you to do? Well, simply put (and easier to say than to do) is to educate yourself and learn more about the different types of weeds and the timing for their control. The first step is to identify the weed and know in which group it belongs. This tells you when it is the best time for control. Let’s look at a few groupings:

  • Annual grassy weeds are best controlled by using a preemergent in the early spring. These products work by attacking the weed seed as it germinates and, thus, preventing establishment.
  • Perennial grassy weeds may be the most difficult to control, as it is hard to kill a grass within a grass. Perennial grassy weeds are normally spot sprayed with a non-selective herbicide that also kills the bluegrass or tall fescue. The trick to good control is to also make sure the intended weed is actively growing. The timing could be spring, summer or fall.
  • Perennial broadleaf weeds, like perennial grassy weeds, are also the most difficult to control. Their extensive root system is loaded with stored food and energy, and often gives them a second chance for survival after treatment. Perennial broadleaf weeds can be treated either in spring or fall, but they must be in an active growth stage for best control.
  • Annual broadleaf weeds must be broken down into at least two groups: cool season and warm season. Warm season broadleaf weeds normally become most obvious in the heat of summer when the grass is stressing. Their control is best achieved in early spring before they become full grown. Cool season broadleaf weeds often germinate during the cool, early fall months. They spend the winter as small plants that then burst into flower as the warmer spring days arrive. Control of these is best achieved in the mid-fall, with only spot spraying in the spring.
  • Sedges. Let’s not for forget about the sedges, which fit into their own category, which means most of the products used to kill grassy and broadleaf weeds have no effect on this plant group.

Use the correct herbicide

The good news for those attempting to rid their lawns of pesky invading weeds is that newer herbicides are now available that will take care of weeds more effectively. Annual grassy weed controls now only require one application of products such as Dimension or Barricade. Triclopyr, Trimec mixtures and Carfentrazone products are much more effective in wiping out broadleaf weeds in the fall. Unfortunately most of us still resort to the Glyphosate products to kill perennial grassy weeds.

Prevent herbicide collateral damage

As with any pesticide products used in the landscape, caution should always be taken before applying. As previously stated, know your weed, the best timing for its control, and the best product to use. I can tell you countless stories of people applying insecticides to kill weeds or herbicides to kill insects, with disastrous results. So, become educated and know what you are doing before causing harm to the environment.

The Johnson County Extension office receives thousands of calls each summer. The number one problem we see is not caused by an insect or a disease, but is man-made. Can you guess what it is? It is damaged landscape plants caused by herbicide drift. The damage is normally not in your own yard but in your neighbors’ up and down the street, as these products can drift for blocks in the breeze.

Here are some simple tips to reduce herbicide damage.

First, limit their use. Can you tolerate a few weeds in the lawn? Would it hurt to bend over and hand-remove a few dandelions in the spring?

Second, time their use. Fall application to control many weeds is recommended over spring treatments. Fall treatments are applied when many of the trees and shrubs are going dormant for winter. Their leaves have shut down production. In the spring, trees and shrubs are in a very active growth stage. This rapid growth makes them easy prey for a little herbicide drifting on the breeze to be up taken and cause damage.

Other easy tips to reduce non-target damage are to spray or treat on cooler days and when the winds are calm. Larger droplets of water are also less likely to drift than a fine spray mist coming from the nozzle. Lastly, when possible use a granular product over a liquid, as they are less likely to drift.

We might as well face it, weeds are here to stay in the lawn. Our KC climate makes lawn care challenging, which gives weeds the opening they need to grow. We also need to stop and think before we act. It is often this impulsive reaction to a weed infested lawn that leads to unintended outcomes, either in our yard or the innocent neighbor down the street.

K-State Research and Extension Johnson County Master Gardener logo

Have questions? The Garden Hotline is staffed by trained EMG volunteers and Extension staff who will assist you with questions.

Phone: (913) 715-7050

Email: garden.help@jocogov.org