Fall Is the Time to Beat Henbit and Chickweed
Henbit, chickweed, and speedwell sprout in fall and bloom in spring. Spraying them in spring rarely works. Here is when and how to control them, from K-St...
Published by ThriveThyme
weeds lawn henbit chickweed fall winter annuals
The Short Answer
Henbit, chickweed, and speedwell are winter annuals. They sprout in fall, sit small through winter, and bloom in spring. By the time you notice the purple or white flowers, a weed killer will usually just burn them back, not kill them. The best window is late October to early November, after most of them have come up, on a day that is at least 50F. If you missed it, keep mowing in spring. The heat of early summer kills them anyway.
How to Tell Them Apart
| Weed | Stem | Flowers | Notes |
|---|---|---|---|
| Henbit | Square | Pinkish purple, small trumpets, heavy in April | Rounded, deeply veined leaves under 1 inch; upper leaves attach right to the stem |
| Common chickweed | Round | Tiny and white | Low, spreading mats |
| Speedwell | Round | Small, often blue or white | Controlled the same way as henbit |
Rolling the stem between your fingers is the fastest test. Square means henbit.
Why Spring Spraying Disappoints
All three weeds germinate in fall and spend the winter as small, established plants. In spring they are older, tougher, and close to the end of their life anyway. Purdue and K-State Extension both note that spraying them at that stage is usually a waste of time and money. Plants may yellow and curl, but they are rarely killed.
There is good news in that, too. Because they are annuals, they die on their own once the weather turns hot. A spring outbreak will not last into summer, and mowing keeps the flowers down until it does.
Your Fall Options
K-State lays out two approaches. Either one works. The difference is timing.
| Approach | When | What it does |
|---|---|---|
| Preemergence | Early to mid September | Stops winter annuals from sprouting at all |
| Postemergence broadleaf spray | Late October to early November, on a day of 50F or warmer | Kills plants that have already come up |
Preemergence. Products labeled for both henbit and chickweed include prodiamine, dithiopyr, isoxaben, and pendimethalin. Purdue adds oryzalin, but notes it is not labeled for speedwell. For this year, the September window has passed. Mark it on next year's calendar.
Postemergence. Wait until most of the henbit has sprouted, then use a broadleaf lawn herbicide such as a 2,4-D product or a three-way mix. These still work below 50F, but the weeds die more slowly. This timing lines up with fall dandelion control, so one trip can handle both.
Some henbit keeps sprouting through late fall and winter, so expect to spot-treat a few plants in early spring (March) no matter which route you pick. Spot-treating is more common after a preemergence program. Always read the label. Follow it for rates, temperatures, and which grasses it is safe on.
In Garden Beds
Lawn herbicides do not belong in vegetable or flower beds. In beds, these weeds are easy to handle by hand:
- Pull or hoe them in fall while they are small and the soil is moist. Their roots are shallow.
- Get them before they bloom in spring. Each plant that sets seed adds to next fall's crop.
- Cover cleaned beds with mulch, leaves, or a cover crop so bare soil does not invite new seedlings. See cover crops for the home garden.
The Long-Term Fix: Thick Turf
K-State notes that henbit does not compete well in a dense, healthy lawn. Thin spots are where winter annuals move in. Good mowing, watering, and feeding habits cut down on how much herbicide you need.
Next Steps
- Walk the lawn this week. Look for small, square-stemmed henbit and white-flowered chickweed rosettes.
- If you plan to spray, pick a calm day of 50F or warmer before mid November.
- Hand-pull seedlings in garden beds, then mulch.
- Put "preemergence, early September" on next year's calendar.
- In spring, mow and wait. Summer heat will finish them.