Scouting for weeds: henbit and purple deadnettle

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.

Henbit (Lamium amplexicaule L.), family: Lamiaceae (Mint). (view images)

Life cycle: Square-stemmed winter annual.

Leaves: Cotyledons are oval in outline and notched at the base where the hairy petioles attach. Opposite, circular to heart-shaped, hairy leaves have rounded teeth along the margins. Prominent, palmately veined leaves give a crinkled leaf surface. Lower leaves are attached by long petioles; upper leaves lack petioles and encircle the stem.

Stems: Square, hairy, spreading stems with many ascending branches from the base can root at the lower nodes. Stems are up to 16 inches tall.

Flowers and fruit: Pink to purple flowers in a two-lipped tube form in whorls in the upper leaf axils. Each flower produces four egg-shaped, one-seeded, grayish brown and speckled nutlets.

Reproduction: Seeds.

Similar weed: Purple deadnettle (Lamium purpureum L.). Differs by having more triangle-shaped leaves, upper leaves with petioles and red to purple coloration.

Control: Henbit and purple deadnettle are winter annual plants that flower and produce seed in early spring. Typically, these seeds will emerge in the fall, overwinter and then resume growth in early spring. Control of henbit and purple deadnettle will depend upon location. Timely applications in the fall and/or preemergence products can work very well in landscape beds. Once in flower, however, herbicide applications are usually not recommended as seeds will quickly mature on the plants. For now, just enjoy their beautiful flowers.

Note: Identification information for more weeds is available in the new field guide An IPM Pocket Guide for Weed Identification in Nurseries and Landscapes. To order, call 517-353-6740 or visit: http://www.ipm.msu.edu/pdf/pocketGuidesLandsc07.pdf

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