Weed of the Month (December 2010)

Henbit

By Peggy Wright MG 2007 Photos by MG Herman Auer

uestion: During the last two clusters occur at the axil of a stem and upper Scientific Qwinters, my lawn was overgrown leaf. The blooming period occurs primar- by weeds that grow in clumps. The weed ily during late winter and spring. However, Name produced rather attractive flowers that under our mild winter weather, some plants Lamium amplexicaule are purplish-colored and trumpet-shaped. also bloom during late fall for about a Should I be concerned with these clumps of month. Each flower typically produces four Other weeds? triangular-shaped seeds nutlets (Figure 4). ommon Answer: The weed in question is very Thus, a healthy plant is capable of produc- C likely to be Henbit (Lamium amplexicaule). ing hundreds of seeds! Name While several other weeds are more com- Will henbit pose a problem in your lawn? Deadnettle, Common Henbit, Giraffe Head monly known and present more widespread If the population is small, enjoy the flowers & Henbit Deadnettle problems in lawns, Henbit can spread ag- for a bit but certainly do not let henbit set gressively if not properly managed. Henbit seeds. Hand-pulling is a viable means of has a strong preference for disturbed areas control when only a few plants are involved. (ex., bare spots, thinning lawn, etc.) and Maintaining a healthy turf (including edges of yards. proper fertilization) to provide competition Henbit is native to Eurasia and Africa will help deter weed establishment. Regular and is thought to have arrived in the USA in mowing at the proper height for the lawn lawn seed during the 1920’s. It is a broadleaf type can help minimize weed growth and plant (dicot) that grows in clumps (Figure invasion in addition to reducing seed pro- 1). Reproduction is primarily by seed but duction. Remember, allowing a few plants it can reproduce vegetatively by the stems with pretty flowers to go to seed can result rooting at the nodes. Henbit is classified in major infestations later on. as a winter annual. Hence, homeowners If henbit is a more serious problem in the typically first observe it during late winter lawn, more aggressive control measures may and early spring in the Texas Upper Gulf be in order. Several pre-emergent herbicides Coast region. While this weed is usually first provided good control of henbit. It is very observed during late winter and early spring, important that the pre-emergent application its seed germinates during early fall upon coincide with the germination period of the the onset of cool temperatures. target weed or weeds. As stated, henbit is a Henbit is a member of the mint family winter annual. It germinates with the onset and has square stems. The first true leaves of cool weather conditions during fall. In are rounded and coarsely toothed with vis- Galveston County, pre-emergent granular ible netted veins. On mature plants, lower herbicides should be applied during the first leaves are attached to leaves by short stalks two weeks of October. (know as petioles). The upper leaves where the flowers occur lack petioles (know as ses- sile) and wrap around the stem. The leaves are thick textured with pronounced veins and circular in shape. Leaves occur opposite (i.e., in pairs) along the stem and leaf mar- gins have rounded teeth. The attractive flowers are reddish (especially unopened flowers, Figure 2) to purplish when fully expanded (Figure 3), slender, tubular (trumpet-shaped), 2‑lipped and 1/2 to 3/4 inch (13 ‑ 19 mm) long. Flowers are produced in a cluster with each cluster containing 6‑12 flowers. Flower