Take Care with Weed Control Products

Home Grown  by Keith Reed
Last week’s rain and this week’s warm temperatures are just what our landscape weeds needed to explode with growth. While I talk about weeds quite a bit in this column, the questions we continue to get in the Extension office suggest it bears repeating.

Now is NOT the best time to control these weeds. Is it possible? Yes it is, but it is certainly not the preferred option. Before I talk about why, it is necessary to talk just a bit about the life-cycle of the weeds and the herbicides (weed killers) that we use to control them.

Spring weeds such as henbit, chickweed, shepherd’s purse, carolina geranium, dandelion and white clover are actually winter weeds by definition. This means they germinate in the fall, grow slowly during the late fall and winter, and then rush to complete their life cycle in the spring. (Note, it is a little more complex than this with clover and dandelions being long-lived perennial weeds, but for control purposes we can include them in this list).

The most common herbicides used to control these weeds contain the active ingredient 2,4-D or a closely related chemical. While these products are very effective in controlling weeds, they do have two characteristics that can cause significant problems when used carelessly. First, they generally kill or at least damage ALL broadleaf plants, not just the weeds that are giving us problems. Secondly, they can easily volatilize and drift surprisingly long distances in the wind.

These two characteristics are what cause many homeowners quite a bit of grief in the spring as it is very easy to mistakenly damage your garden/landscape plants without realizing it. Seedlings and mature plants with new leaves are especially sensitive. Every spring, we look at many samples where careless herbicide application has damaged a crop or important landscape plants.

Even if off target damage was not an issue, we still have two other potential problems to overcome. As weeds mature and begin to go to seed, they become less resistant to herbicides and increasingly difficult to control. This can tempt the applicator into increasing the product rate (unfortunately sometimes beyond the labeled rate). Our turfgrasses are just like our other landscape plants in that they are putting on lush new growth. During this stage, they are also more susceptible to herbicide damage.

Where does this leave you for weed control options right now? Hopefully, straight to your calendar where you can jot yourself a reminder to be proactive next year and treat these weeds in late winter when they are small, easy to control, and there is nothing growing close by that is likely to be damaged by the products you use.

One more note that always bears repeating when we are talking about pesticides of any kind. Always read the label and follow the directions. The label is considered a legal document and failure to follow proper instructions is a violation of the law.

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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