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We continue to experience really cold temperatures in the Tulsa area this winter. I've written about how extreme cold temperatures could affect bermudagrass turf in a negative way. Winterkill is always something turfgrass managers worry about when temperatures hover around zero for very long. We shall see later this spring how our turf has held up. And, we still have some winter to go before spring does get here. Some of the most susceptible times for bermudagrass is in late March and early April, when even temps in the mid-20's can damage grass that has already started to green-up.

But what about pre and post-emergent weed-control

? Does this very cold weather affect it now? Pre-emmergents are watered into the soil where they are activated and stop weed seeds from germinating for many months. Cold weather does not affect that at all, with the product staying in the very top layer of soil and waiting for warmer soil temperatures along with seed germination. The pre-emergent must be applied and into the soil well before any weeds begin to germinate, so these products need to be applied often when it's cold in early spring. They really don't break down much until the soil temperatures rise and the soil stays damp.

Any existing winter annual weeds are still fairly small with the cold temperatures. Generally, they are much easier to control when small. In fact, that's one big reason we treat those the previous fall for our existing customers, so they do not have hardly any weeds now that need to be controlled. New customers however often have alot of weeds, so they need to be treated with post-emergent herbicides. At LawnAmerica, we use two products on bermudagrass and zoysiagrass, Trimec and Atrazine. The Trimec will kill broadleaf weeds, but very slowly when it is this cold. The Atrazine is soil absorbed, so provides us with even better control on broadleaf weeds and grassy weeds such as Poa Annua. Again though, it works very slow during cold weather. As temperatures rise, the weeds will die out faster, but they will also be larger then and harder to control at the same time.

The cold weather mainly affects our guys who are applying the products……brrrrrrrr! And, homeowners need to water in the product within a few days, even though it may be cold. However, it seems latelly that it could be freezing cold one day, and a few days later you can be working outside in your shorts as I did Sunday afternoon. Spring will be here soon enough, and we can't wait here at LawnAmerica!

One Response to “How Does Cold Weather Affect Weed-Control?”

  1. Tom Hills

    What about Mallow which has been removed but the holes (assuming there are hidden seeds in there somewhere) are exposed.
    Would the freeze kill those seeds or can I apply chemicals directly to the holes assuming the day time temperature is in the 50’s?

    Reply

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