Henbit in Your Lawn: How to Identify and Control This Winter Weed

At TurnKey Lawn Care, winter weed control is part of the seasonal care we provide across the metro. If henbit shows up in your lawn every spring, request a free estimate and we’ll plan the fall and winter steps that keep it out.

This guide covers how to recognize henbit, why it takes hold in thin lawns, when to prevent it, how to treat it once it’s up, and how to thicken the lawn so it has less room next year.

How to identify henbit

Henbit or purple deadnettle

An LSU AgCenter home lawn article notes that henbit is commonly confused with purple deadnettle. Both are members of the mint family, both have square stems and both carry purple flowers in spring. For lawn purposes, the distinction rarely changes what you do. Both are cool-season broadleaf weeds that sprout in fall and winter, so the same fall prevention and the same broadleaf postemergence approach apply to each. What matters more is telling henbit apart from grassy winter weeds like Poa annua, because grassy and broadleaf weeds usually need different products. Our post on Poa annua in Louisiana lawns covers the grassy side.

Why henbit takes hold

LSU says henbit can be found growing in areas with thin turfgrass and can tolerate some shade. That’s a good description of many New Orleans lawns going into winter. Several common conditions give it room:

• Summer damage from chinch bugs, drought or disease that never fully filled in
• Shade under live oaks and along the north side of the house, where St. Augustine thins
• Lawns mowed too short through the growing season
• Bare soil along edges, walkways and beds

Henbit spreads by seed, so a yard that had it flowering last spring almost always has seed in the soil for this winter. Each plant allowed to flower adds to that supply. Seed also travels. Mowers, string trimmers and foot traffic carry it from one part of the yard to another, which is why henbit often appears first along paths and edges before spreading into the open lawn.

Prevent it in early fall

Henbit belongs to the group of winter annual weeds that sprout as the weather cools. An LSU AgCenter article on fall lawn care names henbit among the troublesome winter weeds and notes that preemergence herbicides applied in early fall can help prevent many winter annual weeds from becoming established. LSU lists several preemergence active ingredients for henbit, including atrazine, simazine, isoxaben, oryzalin, dithiopyr, prodiamine and pendimethalin. Not every one is labeled for every lawn grass, so the product choice depends on what you’re growing. A straightforward fall routine:

1. Plan the application for early fall. Put it down before the first cool spell, so the product is in the soil when seed starts to germinate.
2. Choose a product labeled for your grass. Confirm the label lists St. Augustine, centipede, zoysia or Bermuda, whichever you have.
3. Measure the lawn and spread evenly. Label rates are per 1,000 square feet, and even coverage matters more than extra product.
4. Water in as the label directs. Many granular products need rain or irrigation to move into the soil.
5. Skip heavy fall nitrogen. LSU warns that excess nitrogen late in the year can stimulate tender growth when the lawn should be preparing for dormancy.

Our guide to pre-emergent weed control timing in Louisiana shows how the fall and late-winter applications fit together.

Treat henbit that's already growing

If henbit is already up, a postemergence broadleaf herbicide is the usual approach. LSU lists options that include combinations with 2,4-D, dicamba and metsulfuron, and stresses following the manufacturer’s labeled directions. Young plants treated in late fall and early winter are easier to control than large, flowering plants in late February, and treating before flowering keeps them from adding seed to the soil. Turf safety is the other consideration. Broadleaf herbicides are formulated for specific lawn grasses, and a product that’s safe on Bermuda may injure St. Augustine or centipede. Our pages on post-emergent weed treatment and when to apply weed killer cover how we time broadleaf treatments on local lawns. In a small lawn with scattered plants, pulling is a reasonable option. Henbit’s roots are shallow, and plants come out easily from moist soil, especially before they flower. Whichever route you choose, the goal for late winter is the same: no flowering henbit left standing by the time spring arrives. Every plant removed before it seeds is one less source of next year’s crop.

Mow at the right height to keep turf dense

LSU’s cultural advice for henbit is the same foundation that works against most lawn weeds: proper fertilization, soil pH management and regular mowing at the right height for your grass. It gives these mowing heights by species:

Lawn grass	LSU mowing height
St. Augustine	2.5 to 3 inches
Centipede	1 to 2.5 inches
Zoysia	1 to 2.5 inches
Bermuda	1 to 2 inches

Mowing within those ranges through summer keeps the lawn thick going into fall, which leaves fewer bare spots for henbit seed to land on. Our page on proper mowing height for Gulf Coast grasses explains how height affects each grass.

A winter weed calendar for New Orleans lawns

Henbit control works best as a yearly cycle rather than a February emergency:

• Summer: mow at the right height and repair thin areas so the lawn goes into fall dense
• Early fall: apply a preemergence herbicide labeled for your grass, before the first cool spell
• Late fall and early winter: spot-treat or pull young plants while they’re small
• Late winter: remove any flowering plants before they set seed
• Spring: thicken bare and shaded areas once the warm-season grass is actively growing

Our page on winter lawn care for Louisiana covers the rest of what a dormant warm-season lawn needs through these months.

Henbit in shaded lawns

LSU notes that henbit can tolerate some shade, and that’s where it often wins in older New Orleans neighborhoods. St. Augustine under a live oak canopy, or along the north side of a raised house, tends to thin out over the years as the trees grow and the shade deepens. That thin, shaded turf is ideal for henbit through the winter, when the tree canopy may let in a little more light and the grass beneath is dormant. Treating the weed each spring without addressing the thin turf means treating it again every year. In deep shade, the long-term answer may be a different planting rather than more grass. Our guide to the best ground cover for shady yards covers options that hold up where St. Augustine struggles.

Common mistakes with winter weeds

Most repeat henbit problems trace back to a few habits that are easy to fix once you know them:

• Waiting until the lawn turns purple in February, when the plants are large and have already started flowering
• Spraying a broadleaf product that isn’t labeled for St. Augustine or centipede and injuring the lawn grass
• Scalping the lawn in late fall to tidy it for winter, which opens more soil for seed
• Pushing heavy nitrogen in fall to keep the lawn green, which LSU warns stimulates tender growth before dormancy
• Treating the weed every year without repairing the thin or shaded turf it’s growing in

Avoiding those five usually cuts the problem down within a season or two. The fall preemergence application does most of the work, and a dense lawn does the rest.

Frequently asked questions