Winter Weeds on the March
By Gretchen Spencer, Fairfax Master Gardener
Among the weeds classified as broadleaf winter annuals are chickweed (Stellaria media), purple deadnettle (Lamium purpureum), hairy bittercress (Cardamine hirsuta), henbit (Lamium amplexicaule), knawel (Scleranthus annuus), shepherd’s purse (Capsella bursa-pastoris), and corn speedwell (Veronica arvensis). This article will compare and contrast two easily confused winter weeds: purple deadnettle (Lamium purpureum) and henbit (Lamium amplexicaule). Previous articles on this website were devoted to hairy bittercress and to wild onion, the latter a broadleaf perennial weed.
Henbit and deadnettle belong to the mint family (Lamiaceae). They were introduced to this country and are native to northern Africa and Eurasia. They can be found growing in lawns, along roadsides, and in disturbed areas, gardens, and fields. As they bloom early in the spring, they provide food for spring pollinators, and both plants are edible. The common name henbit suggests that the seeds were eaten by chickens. The common name deadnettle refers to the fact that its leaves look like those in the nettle family; however, they have no sting. Hence, the plant was named “deadnettle.” Below is a chart that compares the characteristics of the two plants.
|Leaves||Opposite, rounded to heart-shaped; hairy||Opposite, heart-shaped to triangular; sparsely hairy; upper leaves clearly red or purple|
|Leaf margins||Rounded teeth||Scalloped|
|Petioles (leaf stems)||Lower leaves have petioles; upper leaves sessile (stemless)||All leaves have short petioles|
|Stems||Square; lie on the ground; tips grow upward; green or tinged purple||Square; grows more upright|
|Flowers||Pink to purple tubular flowers; grow in whorls; 2/3 inch long||Purple-red flowers; grow in whorls of 3-6; 1-2 cm long|
|Fruit||Egg-shaped nutlets||Egg-shaped nutlets|
|Reproduction||Roots at nodes and by seed; self-pollinating||By seed only; self-pollinating|
Henbit and deadnettle can both spread rapidly. Henbit’s stems can root where they touch the ground. One henbit plant can also produce from 200 to 2,000 or more seeds.
Herbicides may be a more effective method when there is a large area to control. The Virginia Pest Management Guide recommends using a pre-emergent herbicide in the fall, as annual winter weeds germinate when temperatures fall below 75 degrees Fahrenheit. The Guide also recommends using a post-emergent herbicide on broadleaf weeds any time they are actively growing, although the best control is achieved when the weeds are young and before they flower and set seed. Specific herbicide recommendations can be found on the Virginia Cooperative Extension website.
Can you tell whether this is henbit or purple deadnettle? If you said, henbit, you are correct! The sessile (stemless), rounded, upper leaves are identifying characteristics.
Virginia Tech Weed Identification Guide, Virginia Cooperative Extension
Weeds of the Northeast, by Richard H. Uva, Joseph C. Neal, and Joseph M. DiTomaso, 1997
Henbit, HGIC 232, Clemson Cooperative Extension
Weed of the Month: Purple Deadnettle, by Saara Nafici, Brooklyn Botanic Garden
Purple Deadnettle and Henbit, by Larry Steckel, University of Tennessee Extension W165
A Field Guide to Wildflowers of Northeastern and North-Central North America, by Roger Tory Peterson, 1968
Home Grounds and Animals, Pest Management Guide, 2016, Virginia Cooperative Extension