Henbit: Identifying and Removing the Purple Weed

Henbit (Lamium amplexicaule) is a winter annual broadleaf weed that causes some confusion in early spring because it flowers before most other weeds are visible, producing distinctive purple blooms when lawns are still patchy and cool-season grasses are just beginning to green up. It is often mistaken for ground ivy or other purple-flowered plants, but its annual life cycle means it dies naturally in late spring, the challenge is preventing it from seeding heavily before it does.

Page Contents

Identifying Henbit

Leaves: Rounded to heart-shaped leaves with scalloped (crenate) edges. Upper leaves are attached directly to the stem without a stalk (sessile), clasping the stem at their base, hence the species name amplexicaule, which means “stem-clasping.” Lower leaves have short petioles. Leaves are downy or hairy on both surfaces.

Stem: Square in cross-section, characteristic of the mint family (Lamiaceae). Stems are weak and tend to sprawl along the ground before turning upright.

Flowers: Small, tubular, pink to purple flowers arranged in whorls around the upper stem nodes. Flowers appear in early spring, often as early as February to March in mild climates. The purple flower color in an otherwise brown or dormant lawn is the most noticeable identification feature.

Height: Low-growing, typically 4 to 12 inches tall.

Commonly confused with: Purple deadnettle (Lamium purpureum), a close relative with similar flowers but with purple-tinged upper leaves that distinguish it from henbit. Ground ivy (Glechoma hederacea), a perennial rather than annual, with rounder leaves and a strong mint-like smell when crushed.

Life Cycle and Why It Appears When It Does

Henbit is a winter annual. It germinates in late summer or fall when soil temperatures drop below 70 degrees Fahrenheit, typically September to November in most of the US. It grows as a low rosette through winter and then bolts and flowers in early spring as temperatures begin to rise. After flowering and setting seed, it dies as summer heat arrives.

This life cycle means that by the time homeowners notice the purple flowers in early spring, the plant is already at or near the end of its active growth period and approaching seed set. Treating it with post-emergent herbicide at the flower stage is still effective at preventing seed set, but the most efficient control is preventing germination in fall with a pre-emergent application.

Control: Pre-Emergent in Fall

The most effective and efficient control strategy for henbit is a pre-emergent herbicide applied in early fall before seeds germinate. By preventing germination, the entire winter growth cycle, spring flowering, and seed set are eliminated.

Timing: Apply in late August to mid-September before soil temperatures drop below 70 degrees Fahrenheit. In most of the US, this is the same timing window used for annual bluegrass (Poa annua) pre-emergent control.

Effective pre-emergent products for henbit:

Isoxaben (Gallery): The most effective pre-emergent for winter annual broadleaf weeds including henbit. Often combined with a grassy weed pre-emergent for broader fall spectrum control.
Pendimethalin: Controls henbit in addition to its primary target weeds (crabgrass and annual grasses). Available in many consumer pre-emergent products.
Trifluralin: Available in some consumer lawn products. Controls henbit along with other winter annual broadleaf weeds.

Control: Post-Emergent in Late Winter to Early Spring

If henbit has already germinated and is growing but has not yet flowered, a post-emergent broadleaf herbicide application in late winter (January to March depending on climate) kills the plants before they set seed.

Effective post-emergent products for henbit: Standard three-way broadleaf herbicides containing 2,4-D, dicamba, and MCPP control henbit effectively when plants are actively growing before or early in the flowering stage. Products such as Spectracide Weed Stop for Lawns, Ortho Weed B Gon, and equivalent generic products provide reliable control.

Application timing: Apply when henbit is actively growing, temperatures are above 45 degrees Fahrenheit, and no frost is forecast within 24 hours. Applying at the pre-flower stage is more effective than waiting until full bloom.

Do not delay treatment until flowers appear and mature: At or after peak bloom, plants are already producing seed. Treatment at this stage still kills the plant but may not prevent all seed from maturing if the plant is in late flower.

Hand Removal

Because henbit is annual with a shallow root system, hand removal is practical for small infestations. Pull plants before they flower and set seed, removing the root as completely as possible. Dispose of pulled plants in a bag or trash, do not compost, as flowers at any stage may continue maturing seed even after the plant is detached.

Hand removal is most practical in early spring on moist soil. On larger infestations, herbicide treatment is more efficient.

Long-Term Prevention

A pre-emergent herbicide applied every fall is the most reliable long-term prevention strategy for lawns with recurring henbit problems. Dense turf coverage suppresses henbit establishment in lawn areas, because henbit is a poor competitor against established, well-fertilized grass, it establishes most readily in thin, bare, or poorly covered turf.

For lawns that are consistently thin in fall, providing openings for henbit germination, improving turf density through overseeding and fall fertilization is a foundational part of long-term prevention. See lawn fertilizer schedule by season and grass type for the fall fertilization timing that builds the dense turf that suppresses henbit naturally.