Act Now to Prevent Pesky Weeds in the Spring

Home Grown  by Keith Reed
Note: We’ve touched on this topic recently. Here are some helpful details. Now is the time!
One of the things we can count on in the Extension office is an overwhelming number of phone calls and walk-ins in late spring when the spring weeds begin to explode. Annual bluegrass, chickweed, and henbit are the three of the most common weeds in our area, but there are many other species that also cause problems.

Even though these are often referred to as spring weeds since that is when they become an issue, these are actually classified as “winter annual” weeds. This is an important point as the life cycle determines the best time to attempt control. By definition, winter annual means the weed germinates in the fall, grows very slowly throughout the winter, and then completes its life cycle in the late spring or early summer. This means the weed is at full strength when it becomes a problem, and thus, much more difficult to control.

The ideal way to control these weeds is to apply a fall-pre-emergence product now before these weeds germinate. The key word is before as pre-emergent products do nothing to control weeds after they have already come up. In our area, this usually means around the first week of September as we begin to get our first fall cool fronts and (hopefully) rains.

Look for lawn pre-emergent products containing the active ingredient prodiamine or pendamethalin. For weed control in ornamental beds, the key ingredients are dithopyr, isoxaben, or trifluralin. NOTE: It is very important to avoid combination products in ornamental beds that are made to kill existing weeds in addition to providing pre-emergent control as these can harm your desirable plants. These chemicals can be purchased in several different formulations including granular and sprayable products.

Looking for the products mentioned above should only be the starting point for selecting a product. Failure to read the label and follow the instructions will result in disappointing results and could possibly cause damage to your landscape. Just one example: the label will provide specific instructions about post application watering. This is extremely important so the product can be moved into the soil layer where it does its work in a gaseous form. If it is not watered in, it will be worthless.

One last important point of consideration: Do not apply these products if you have a brand new stand of grass or are planning on seeding this fall. Once again, this information is covered on the label, but unfortunately it is a detail that is often overlooked. These products will prevent turfgrass and ornamental seeds from germinating just as well as weed seeds.

For more information on this or any other horticultural topic, you can contact Keith Reed, the Horticulturist in the Payne County Extension office. Keith can be reached via email at
keith.reed@okstate.edu, phone at 405-747-8320, or in person at the Payne County Extension office, located at 315 W. 6th in Stillwater.

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