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Henbit

Description

Henbit (Lamium amplexicaule) is a sparsely hairy, winter annual weed with greenish to purplish, tender, square stems. Its opposite leaves are broadly egg shaped with bluntly toothed margins and prominent veins on the underside. Upper leaves are sessile (directly attached to the stem), and lower leaves have petioles. It has a fibrous root system and can grow to a height of 16 inches. Henbit’s distinctive flowers are reddish-purple with darker coloring in spots on lower petals. It blooms in the spring with the flowers arranged in whorls in the upper leaves.

Henbit has a prostrate growth habit that is difficult to control by mowing. Steve Dewey, Utah State University, Bugwood.org

Henbit has a prostrate growth habit that is difficult to control by mowing.
Steve Dewey, Utah State University, Bugwood.org

A top view shows henbits coarsely toothed leaves and reddish-purple flower buds. Karen Russ, ©2009 HGIC, Clemson Extension

A top view shows henbits coarsely toothed leaves and reddish-purple flower buds.
Karen Russ, ©2009 HGIC, Clemson Extension

Henbit is found throughout most of South Carolina. It most commonly occurs in open disturbed sites, often in fields and along roadsides. It is also found in home lawns.

Henbit is commonly confused with purple deadnettle (Lamium purpureum). However, purple deadnettle has triangular upper leaves, on petioles, and distinctly red- or purple-tinted, unlike the upper leaves of henbit.

A side view of henbit shows its square stems and purple flowers. Karen Russ, ©2009 HGIC, Clemson Extension

A side view of henbit shows its square stems and purple flowers.
Karen Russ, ©2009 HGIC, Clemson Extension

Purple dead nettle with triangular leaves and purple leaf coloration is often confused with henbit. Karen Russ, ©2009 HGIC, Clemson Extension

Purple dead nettle with triangular leaves and purple leaf coloration is often confused with henbit.
Karen Russ, ©2009 HGIC, Clemson Extension

Cultural Control

Henbit is a winter annual, broadleaf weed that reproduces by seed that germinate in the fall or winter. Henbit grows during any period of warm weather that occurs in winter. Other than unusual warm weather periods, it remains somewhat dormant during the winter. Henbit resumes growth and produces seed in the spring and dies as temperatures increase in late spring and early summer.

Henbit can quickly invade thin turf areas, especially where there is overly moist soil. Shade also encourages growth. Its growth habit may be prostrate; therefore, plants are not significantly affected by mowing.

A dense, vigorous turf is the best way to reduce the encroachment of henbit. First, select a turfgrass cultivar adapted for your area, and then properly fertilize, mow, and water to encourage dense growth. Water the lawn deeply but as infrequently as possible in the fall, as weed seeds need soil surface moisture to germinate. For more information on growing healthy turfgrass, see HGIC 1201, Fertilizing Lawns; HGIC 1205, Mowing Lawns; and HGIC 1207, Watering Lawns.

In landscape beds, henbit can be hand dug and suppressed with the use of mulch. A 3-inch mulch layer is ideal for reducing weed growth.

Chemical Control

In Lawns: Cultural controls should be implemented before applying herbicides for henbit control. However, chemical control may still be necessary after modifying lawn care techniques to further reduce a henbit population. Herbicides should be carefully chosen according to turf species, and all label instructions followed. Chemical controls for henbit should be applied in fall or early spring for best results. Keep in mind that herbicide effectiveness is reduced as weeds mature.

A three-way herbicide may be used on bermudagrass, zoysiagrass, centipedegrass, St. Augustinegrass, and tall fescue to control henbit, deadnettle, or almost any broadleaf weed in the lawn. The active ingredients of a three-way herbicide include the following broadleaf weed killers: 2,4-D, dicamba, and mecoprop (MCPP) or MCPA. Examples of three-way herbicides for residential lawns in homeowner sizes are:

  • Ferti-lome Weed-Out Lawn Weed Killer – Contains Trimec® Concentrate
  • Southern Ag Lawn Weed Killer with Trimec® Concentrate
  • Bayer BioAdvanced Southern Weed Killer for Lawns Concentrate; or RTS
  • Spectracide Weed Stop Weed Killer for Lawns Concentrate; or RTS
  • Bonide Weed Beater Lawn Weed Killer Concentrate
  • Ortho Weed B Gon Weed Killer for Lawns Concentrate; or RTS
  • Ortho WeedClear Weed Killer for Lawns Concentrate

Note: Herbicides containing 2,4-D should be applied at a reduced rate on St. Augustinegrass and centipedegrass to prevent damage to these lawns. The product labels will give the rate to use for each type of turfgrass. If a second application is needed, apply the herbicide in spot treatments. Repeated applications of a three-way herbicide should be spaced according to label directions.

In addition to three-way herbicides, there are several other herbicides that can be used for henbit control on home lawns. Atrazine may be used to control henbit in centipedegrass and St. Augustinegrass. Atrazine is a post-emergence broadleaf weed killer that also controls several common grassy weeds and has some pre-emergence activity.

Examples of products containing atrazine for residential lawns in homeowner sizes are:

  • Hi-Yield Atrazine Weed Killer
  • Southern Ag Atrazine St Augustine Weed Killer

Note: Read and follow all label instructions when using herbicides. Repeat applications 10 to 14 days apart may be required for acceptable control. Do not mow within 48 hours after the application of most herbicides. Most post-emergence herbicides need to dry on the leaf surface before irrigation or rainfall occurs. See Table 1 for turfgrass tolerance to herbicides.

CAUTION: Herbicides should not be applied during spring transition (green-up of warm season lawns) or when air temperatures exceed 90 ºF, as this can cause severe damage to the turfgrass. A newly seeded lawn should be mowed a minimum of three times before applying an herbicide. Rainfall or irrigation a day or two prior to herbicide application reduces the chance of turfgrass injury and enhances weed uptake of the herbicide.

A more recent herbicide combination of thiencarbazone, iodosulfuron, and dicamba, as found in Celsius WG Herbicide, is selective to control many broadleaf weeds and several grassy weeds in all four of the common warm-season grasses. It cannot be used in fescue lawns but can be used to remove fescue from warm-season lawns. Apply when henbit is actively growing and again 2 to 4 weeks later if needed. The addition of a non-ionic surfactant (such as Southern Ag Surfactant for Herbicides, Hi-Yield Spreader Sticker, or Bonide Turbo Spreader Sticker) at 2 teaspoons per gallon of spray mix will increase control. Celsius WG Herbicide is safe to apply during spring green-up of warm season grasses

Metsulfuron can be used for henbit control in bermudagrass, centipedegrass, St. Augustinegrass, and zoysiagrass. Quali-Pro MSM Turf Herbicide is a product that contains metsulfuron, and Quali-Pro Fahrenheit contains dicamba along with metsulfuron; however, the label directions are written for landscape professionals.

Do not apply metsulfuron to lawn if over-seeded with annual ryegrass or over-seed for 8 weeks after application. Do not plant woody ornamentals in treated areas for one year after the application of metsulfuron. Do not apply metsulfuron herbicides within two times the width of the drip line of desirable hardwood trees or if the temperature is over 85 °F. For these professional products, a non-ionic surfactant (such as Southern Ag Surfactant for Herbicides, Hi-Yield Spreader Sticker, or Bonide Turbo Spreader Sticker) is required at 2 teaspoons per gallon of spray mix for best control.

Table 1. Turf Tolerance to Herbicides for Henbit Control.

Herbicide Bermudagrass Centipedegrass St.
Augustinegrass
Tall Fescue Zoysiagrass
atrazine D S S NR NR
(3- way) 2,4-D + MCPP + dicamba S I I S S
metsulfuron S S S-I NR S
dicamba & metsulfuron S S S NR S
thiencarbazone, iodosulfuron, & dicamba1 S S S2 NR S
S = Safe at labeled rates
I = Intermediate safety, use at reduced rates
NR = Not registered for use on and/or damages this turfgrass
D = Fully dormant turf only. However, during the warmer winter weather of recent years, bermudagrass lawns have not gone fully dormant in South Carolina.
Note: Do not apply post-emergence herbicides, except Celsius WG Herbicide, to lawns during the spring green-up of turfgrass.
1 This mix of active ingredients requires the addition of 2 teaspoons of a non-ionic surfactant (that is, a wetter-sticker agent to aid in weed control at 0.25% by volume) per gallon of water, such as Hi-Yield Spreader Sticker.
2 Spot treatments to St. Augustinegrass at temperatures above 90 degrees may cause temporary growth regulation.

In Landscapes: If henbit is a problem in landscape beds, glyphosate can be used for spot treatments around ornamental plants. Glyphosate is a non-selective herbicide that should be used with caution. Do not allow glyphosate spray mist to contact ornamental foliage or stems as severe injury will occur. A cardboard shield may be used to prevent glyphosate spray from drifting to nearby ornamentals. Younger henbit plants are more susceptible to control with glyphosate than older plants. Examples of glyphosate products in homeowner sizes are:

  • Roundup Original Concentrate,
  • Roundup Pro Herbicide,
  • Martin’s Eraser Systemic Weed & Grass Killer,
  • Quick Kill Grass & Weed Killer,
  • Bonide Kleenup Weed & Grass Killer 41% Super Concentrate,
  • Hi-Yield Super Concentrate,
  • Maxide Super Concentrate 41% Weed & Grass Killer,
  • Super Concentrate Killzall Weed & Grass Killer,
  • Tiger Brand Quick Kill Concentrate,
  • Ultra Kill Weed & Grass Killer Concentrate,
  • Gordon’s Groundwork Concentrate 50% Super Weed & Grass Killer,
  • Zep Enforcer Weed Defeat III,
  • Eliminator Weed & Grass Killer Super Concentrate,
  • Monterey Remuda Full Strength 41% Glyphosate,
  • Knock Out Weed & Grass Killer Super Concentrate,
  • Southern States Grass & Weed Killer Concentrate II,
  • Total Kill Pro Weed & Grass Killer Herbicide,
  • Ace Concentrate Weed & Grass Killer.

If this document didn’t answer your questions, please contact HGIC at hgic@clemson.edu or 1-888-656-9988.

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