With spring coming soon, we will begin to get outdoors to improve our lawns, and just be outside. Make sure you know what weed you are dealing with in your landscape and know the best way to control it. There are times for controlling weeds, it may not be the best in spring for all. Spraying at the wrong time is a waste of money and can be harmful to our environment.
Crabgrass is one of the most problematic weeds in lawns. It is a summer annual weed. Summer annuals germinate in the spring, grow and produce seed throughout the summer and die with the first frost in the fall. Crabgrass germinates when the soil temperatures average 55-60 degrees Fahrenheit. So, crabgrass preventer should be applied when the soils reach that temperature. Typical preemergence herbicides include dithiopyr, prodiamine, or pendimethalin as the active ingredient. A second application should be made in late May to June for season-long control.
If you miss the window for preemergence products, you still have options. There are some great post-emergence products. Dithiopyr and mesotrione have pre- and postemergence activity on crabgrass. Quinclorac is a great postemergence herbicide that is often found in the product Drive. So any of these can be used if you miss the spring window for control.
Annual Broadleaf Weeds
Henbit is a winter annual. A winter annual is a plant that germinates in the fall and grows a bit before basically becoming dormant for the winter months. Very early in the spring, henbit will start to grow again, produce flowers and seed for the next year then it will die when the temperatures warm up. This is different from a summer annual which germinates in the spring and goes through its lifecycle through the summer months and dies with our fall frosts.
The problem with henbit is that by the time we see it, or rather see the purple flowers, it is too late to treat for the year. Once the flowers begin to show up, it is already producing seed for next year, so killing blooming henbit is unnecessary because it will die naturally and the chemicals won’t reduce production for next year. However, pulling the plant would be a fine management practice after blooming has begun. It can be sprayed with a 2,4-D product very early in the spring once it has greened up but before it blooms. If you know where it is you can spray it before it blooms. Otherwise, wait until this fall to spray those areas with a preemergence herbicide before it germinates in the fall.
We have a lot of perennial weeds in our lawn as well. Plants like dandelions, creeping Charlie, and clover are perennial broadleaf weeds. Perennial weeds are best controlled in the fall once the weeds have begun their preparations for winter. In the fall, these perennial weeds will move sugars that they use for energy from the above ground portions of the plant down into the roots to store them for next spring. If they are sprayed during this phase of their lifecycle, they are more likely to take that herbicide down into the roots to be more effective than if done in the spring. Spraying these weeds in the spring will knock them down, but likely not kill them outright.
Nimblewill is a perennial grassy weed. It is controlled through one of two methods. You can spray it with a product containing mesotrione that won’t harm the surrounding grass. Or you can spray it with a glyphosate product, such as Roundup, then overseed the area. The glyphosate will only be effective if sprayed on the nimblewill when it greens up, and this is a warm season grass so it will be later in the summer. It is best to do this in August then you can overseed 2-3 weeks later.
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