Friday, December 01, 2023

I have weeds. What do I do?

| April 18, 2010 9:00 PM

Along with the other traditions of spring such as leaves on our trees, early bulbs popping up in our yards, and the beginning of hay fever season for me and thousands of others, the germination of spring weeds has begun. There are many ways to predict the coming "bloom" of dandelions and other broadleaves, as well as many grassy weeds. Suffice it to say that just before the trees start budding and your lawn wakes up, weeds are already germinating and getting a foothold in your lawn and landscape beds. The first place you'll see them is at the foundation of your house, along driveways, and anywhere that gets warm during the day. Once you see the first one pop up in those artificially warm areas of your yard, it's time to take action.

As is often said, "The best offense is a good defense." In the case of weed control, the best possible way you can keep weeds at bay is to maintain a healthy stand of turf. Weeds are opportunists, in that they get a foothold where turf is thin or generally weak. This is where a sound fertility program is key to keeping weeds at bay without using herbicides. As this is not always possible, it's important to know what to do once we have weeds.

There are two basic classes of weed killers (herbicides). The first are known as pre-emergent herbicides, and the second class are post-emergents. As the name would indicate, a pre-emergent will control weeds before they germinate. Most pre-emergents are completely ineffective at controlling weeds once they have germinated, so timing is critical to get the best control. If you are applying a pre-emergent, make sure the product gets watered within a few days so it can get to the soil level. Once a pre-emergent is applied, avoid aerating or thatching, as this will disrupt the barrier you have created to keep weeds from germinating successfully.

Post emergents, on the other hand, are excellent at controlling weeds that have already germinated. It is important to know that most weeds, especially broadleaves, are annual plants. This means that they germinate in spring or early summer, mature and produce a flower of some form, and then die after spreading it's seeds for the next year. With respect to timing of post-emergent applications, earlier is better. It is far more effective to control a weed that is young and rapidly developing compared to one that has progressed to producing flowers and seeds. A weed must take the chemical in to kill the plant, and if the plant has shifted to seed production, it will not only be very large, but it will be much harder to get the product to move in to the plant to be effective. Post-emergents need to dry on the leaf and stay dry for up to 12-24 hours before irrigating or rainfall.

Finally, read labels of products or ask a salesperson so you know which class of herbicide you are buying. We don't want to apply chemicals incorrectly or at the wrong time.

If you have any questions or feedback contact Kevin Hicks at

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