The saying “timing is everything” could never be more true.
Proper timing of herbicide applications can not only save you the frustration of having a lawn full of weeds, but it can also lead to better control of those pesky plants.
Properly identifying the weed and knowing its life cycle is helpful in selecting the best control method for the greatest results.
Knowing the type of plant you are dealing with is crucial in its control. Annual weeds require a little different approach than perennial weeds. Annual weeds are those that sprout, grow, set seed and die all within a year. Annual weeds fall into one of three categories: Spring annuals like crabgrass; summer annuals like knotweed or sandbur; and winter annuals like henbit. Each one has a different set of temperatures and requirements it needs in order to germinate.
Perennial weeds continue to come up year after year from the crown of the plant, like clover and ground ivy.
There are several options for control of weeds. Knowing the plants’ life cycle and when it germinates will help in the timing of herbicide applications.
Preemergence herbicides keep the seeds from germinating, or sprouting, which keeps the weeds from becoming a problem. Preemergent herbicides are usually used to prevent annual weeds. Once the seeds have germinated, the preemergence herbicides are not as effective at controlling the growing weeds and a different approach might be needed. Preemergence herbicides are not effective in controlling perennial weeds because they come back from the crown every year, not from seeds.
Postemergence herbicide is a common method of control once a weed has germinated. Timing of postemergent herbicide control is just as important as the timing of preemergence herbicide. Early season control of many weeds can give you better efficacy.
In some instances, applications are not as effective. Summer applications of broadleaf weed killers to perennials might just burn back the plant for a little while, only to have it regrow new leaves later in the season.
The best time to get good control on perennial weeds is in the fall after a light frost. Alternatively, late season applications of herbicides to annual weeds might make you feel better, but it will only kill the plant a month earlier than it normally would have due to frost and it could still drop its seeds.
Knowing the plant you are targeting will help you know when is the best time to get control.
Manually removing the weed may require a little elbow grease, but it is also an effective method of postemergence control. Hand pulling or digging will also take a little time. Manually removing the weed from the landscape not only takes out that problematic weed, but it also removes the ripening seeds.
Aim to get the whole root system if possible and get the plant out of the landscape before it has a chance to drop its seeds.
If you have a large area that has too many weeds and needs complete rejuvenation, solarization might be the route for you. With solarization, clear plastic is placed over the area for several months and the ground is ‘baked’ in the hot summer sun to kill seeds or crowns. This is best done over an entire growing season.
Patience is key when it comes to certain weeds. You might think you controlled the problem weed one year, only to see it again a few years down the road. Problematic weeds like Asiatic dayflower and puncturevine have seeds that can remain viable for up to five years. The seeds will sit in the soil and wait for the right conditions or opportunity to germinate. Just when you think you have the problem under control, there they are again. Stay vigilant, eventually you will get control.
Proper timing, identification and selecting the right method are the secrets for good weed control. With a little luck, your weeds might have met their match.
Elizabeth (Killinger) Exstrom is the Horticulture Extension Educator with Nebraska Extension in Hall County. Contact her at 308-385-5088 or email@example.com. Visit the Hall County Extension website at hall.unl.edu
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