Several species of invasive weeds grow in winter, especially in regions with mild winters. The most common winter weeds are Annual Bluegrass, Chickweed, and Henbit. However, there are several other weed species that sprout in fall and thrive throughout winter. You can prevent these weeds from sprouting by spreading pre-emergent in the fall, or attack them with a weed killer once they appear. Winter annual weeds are pesky plants that will return year after year if they aren’t dealt with quickly.
What Weeds Grow in Winter?
Winter annuals are weeds that commonly sprout in late summer or fall in the USA and parts of Canada. Although these weeds are most common in the warm regions of the American South, West, and lower Midwest, they can be found throughout the continental United States. The most common winter weeds are:
- Annual Bluegrass (Poa Annua)
- Common Chickweed
- Shepherd’s Purse
- Yellow Rocket
- Canada Thistle
- Corn Speedwell
- Virginia Pepperweed
It’s easy to spot winter weeds because they won’t die and will appear green and growing as the grass in your lawn goes dormant. In warm areas, you may even see broadleaf annual weeds and perennials. Common weeds visible in late fall include dandelions and clover. These weeds can continue to grow actively even as winter approaches.
How Do You Control Winter Weeds?
In order to prevent weed growth during the fall and winter months, it’s best to stop weed seeds from sprouting with a fall application of pre-emergent herbicide. However, if you missed your pre-emergent window and the weeds have already sprouted, you can kill winter weeds with a targeted herbicide or a natural method.
Pre-Emergent Herbicide for Winter Weeds
If you spread a good pre-emergent herbicide in the fall, you can prevent annual winter weeds from sprouting. This application will halt annual bluegrass, henbit, and chickweed, just to name a few. Pre-emergent herbicide works by killing weed seeds as they sprout, but won’t harm any actively growing grass or plants.
- This excellent pre-emergent kills any weed seeds as they sprout, but won’t harm any grass seed you’ve spread.
- Apply pre-emergent in fall when average soil temperatures drop to 70℉ (21℃) for 2–3 days.
While pre-emergent is great for stopping weeds from sprouting, it won’t kill weeds that have already appeared in your lawn. For this reason, timing is important. Plan to spread your pre-emergent weed killer in the fall. The ideal time is when the soil temperature drops down from summer highs to 70℉ (21℃) for 2–3 consecutive days.
Post-Emergent Herbicide for Winter Weeds
If broadleaf and grassy weeds have already sprouted in your yard during fall, it’s time to tackle them directly. A post-emergent herbicide designed for winter weeds is your best bet. Tenacity, the pre-emergent we recommend for fall application, also works as a post-emergent weed killer. It wipes out winter weeds and perennial weeds like dandelions. Even better, it won’t kill the grass on your lawn.
- Tenacity works as both pre-emergent and post-emergent herbicide that is effective against all types of winter weeds but won’t harm grass.
- By using a dual-action pre-emergent/post-emergent, you will save money and make application easier.
- If your lawn grass is dormant, you can kill invasive grassy weeds and perennial weeds by spraying your lawn with Roundup.
- Roundup won’t harm dormant grass, but it will kill actively growing grass, so only spray it on your lawn if the grass is brown and the weeds are green.
Although Roundup is a non-selective herbicide that kills grass and broadleaf weeds alike, there’s a secret to using it in winter. Roundup won’t harm dormant grass. So, if your lawn has gone brown, you can spray Roundup weed killer on the green patches of poa annua and any other winter weeds that are green and growing in your yard. The weeds will be killed but the grass won’t be harmed.
Natural Winter Weed Removal Methods
If you prefer to keep your lawn chemical-free, you can control winter weeds through natural means. Instead of a chemical pre-emergent, spread corn gluten. This pre-emergent can be spread at the same time you would spread a herbicidal product. It works by drying out weed seeds as they attempt to sprout, killing them.
- Use this organic pre-emergent to prevent weeds from sprouting.
- Spread organic pre-emergent at the same time you would typically spread a herbicidal pre-emergent.
- Control actively growing weeds in fall and winter by hand-pulling.
Because natural weed killers containing vinegar and other household products do not kill weeds down to the root, it’s best to combat all types of weeds in winter by hand-pulling them. Use a weeding tool to remove the weed and as much of the root as possible. It’s best to attack these types of weeds in fall, before the ground freezes.
When Should You Spray Winter Weeds?
The best time to spray winter weeds is when your lawn goes dormant and the winter weeds can easily be identified. The actively growing winter weeds will appear as green splashes on your brown, dormant lawn. This makes it simple to find winter weeds and spray the unwanted weed growth with the herbicide of your choice.
- Spray winter weeds when your lawn has gone brown and dormant.
- You will be able to locate green winter weeds easily in a brown, dormant lawn.
- Herbicide sprayed on dormant grass won’t harm it. This ensures you will kill the weeds only.
In addition to easy identification, there’s another reason to spray winter weeds after your lawn has entered dormancy—weed killers won’t harm dormant grass. You can spray Roundup on a batch of weeds in your lawn without worrying about harming your desirable grass.
How Warm Does it Need To Be To Spray Weeds?
Spray weeds in fall and winter when the temperature is at least a few degrees above freezing and the weeds are actively growing. If the temperature is below 40℉ (4℃), your weed killer spray won’t be effective. Additionally, if the weeds are in the brown, dormant part of their life cycles the weed killer won’t work.
Is it Worth Killing Weeds in the Fall?
Killing weeds that appear in fall helps reduce spring weeds. It also helps stop the spread of weeds, meaning you’ll have fewer weeds next year. Most winter weeds sprout in fall, survive all winter, and then drop their seeds in late spring before wilting. So, tackling weeds in fall is excellent weed control that promotes a healthier, weed-free lawn year-round.
Do Weeds Live Through the Winter?
In many regions of the US, several species of weeds sprout in fall, survive through winter, and drop their seeds in late spring. These weeds rob your soil of nutrients and crowd out desirable plants and grasses. To fight back against winter weeds, spread preemergence herbicide in fall. If weeds are actively growing when your grass has gone dormant, spray them with herbicide or pull these weeds out by hand. You’ll have a weed-free lawn by spring.