Jil Swearingen, USDI National Park Service, Bugwood.org
Purple deadnettle is often confused with henbit because of its square stems and purple-red flowers. Unlike henbit, deadnettle has petioles, the part of the weed that joins the leaf to the stem. This weed is a member of the mint family and produces purple-red flowers in clusters. It germinates in the fall and blooms in the spring, preferring moist and shady areas.
Keeping the grass dense and lush is an effective way to keep deadnettle from actively growing. Proper mowing and fertilization, including irrigation in the spring and summer, will help to prevent an infestation. Applying pre-emergent herbicides containing dithiopyr before germination also provides effective weed control.