Winter annual weeds are blooming and getting ready to invade your gardens – don’t let them get a foothold!
Winter annual weeds include common chickweed, spotted deadnettle, henbit, prickly lettuce, Persian speedwell, bedstraw, wild mustard, cressleaf groundsel, shepherd’s purse, hairy bittercress, and a few others. These weeds germinated last fall and hung around the garden all winter.
They grow slowly over the winter and tolerate cold temperatures. Then, in the spring, they take off like wildfire, growing, flowering, and going to seed.
They don’t tolerate warm temperatures and after they drop seeds, and it gets warm, they die out. Since they don’t hang around during the summer, many gardeners don’t pay them much attention.
Gardeners sometimes think that they appear out of nowhere, but in reality, they have been around since last fall. This fall, the new seeds germinate, and the cycle continues, but with more plants.
If you have them in your lawn, fertilize and encourage a thick stand of turf. This prevents the seeds from germinating. Since they die out in the heat, using a herbicide is fairly useless.
If they are in flower beds or gardens, the first thing to do now is to remove them before they go to seed. This helps to deplete the seed population in the garden.
Herbicides that are labeled for these weeds can be used but do it early before they flower. I have observed some of them go to seed quickly after being sprayed with herbicides.
Keep in mind, if these are in flower beds, herbicides will also damage the good plants as well. Read the label to know how to use the herbicide correctly.
Another herbicide that can be used successfully is preemergent; this prevents them from growing. I find preemergent herbicides combined with mulch provides the best control.
Preemergent herbicides need to be applied before they germinate. Therefore, for winter annual weeds it should be applied to a clean bed in the fall to keep them from germinating.
Mulching the beds helps to prevent weeds from growing, however, it will depend on the thickness of the mulch layer. These seeds will germinate through a thin layer.
Keep in mind, you don’t want a thick layer of mulch on perennial and annual beds. No more than two inches should be used. Around trees and shrubs, you can use up to four inches of mulch.
Always keep the mulch away from the crown or the main stem of the plants.
Don’t forget that we also have summer annual weeds such as purslane, knotweed, spurge, and more. Again, preemergent herbicides and mulch also help with these.
If you are using a preemergent herbicide, check to see how long the product works. If it’s a 90-day control, for instance, you may have to reapply in the spring to prevent the summer annuals from germinating.
Above all, don’t let them go to seed! This just compounds your weed challenges.
Pamela Corle-Bennett is the state master gardener volunteer coordinator and horticulture educator for Ohio State University Extension. Contact her by email at email@example.com.
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