Mint family (Lamiaceae)
Description: This plant is a winter or summer annual (usually the former) that is unbranched and ½–2½' tall. The central stem is strongly 4-angled and largely glabrous. The lower third of the stem in a mature plant is often devoid of leaves. The opposite leaves are up to 2" long and across. They are densely crowded together along the stem, each pair of leaves rotating 90° from the pair of leaves immediately below or above. Young leaves at the apex of the stem are tinted purple, but they become dull green with maturity. The leaves are broadly cordate or deltoid, crenate along their margins, and finely pubescent. Their petioles are short. The upper surface of each leaf has a reticulated network of indented veins, creating a wrinkly appearance.
Sessile whorls of flowers occur above the leaf axils, and a terminal whorl of flowers occurs at the apex of the stem. Each tubular flower is about ½" long and has well-defined upper and lower lips. The lower lip is divided into 2 rounded lobes, and there are insignificant side lobes that are reduced in size to small teeth. The corolla is purplish pink, pink, or white – the upper lobe is usually a darker color than the lower lobe, which is often white with purple spots. The tubular calyx is green or purplish green, and has 5 slender teeth that spread outward slightly. The blooming period usually occurs during mid- to late spring and lasts about 1½ months, although plants that are summer annuals may bloom during the fall. Each flower is replaced by 4 nutlets. The root system consists of a taproot. This plant occasionally forms dense colonies by reseeding itself.
Cultivation: Typical growing conditions are full sun to light shade and moist fertile soil. The foliage is little bothered by disease and insect pests. This plant develops quickly during the cool weather of spring.
Range & Habitat: The adventive Purple Dead Nettle occurs occasionally throughout Illinois, except in the NW counties, where it is rare or absent. It is somewhat less common in the northern half of the state, as compared to the southern half. This plant is native to Eurasia. Habitats include moist fallow fields, banks of ditches and drainage canals, gardens and nursery plots, weedy edges of woodlands, and various kinds of waste ground. Degraded sites with a history of disturbance are preferred.
Faunal Associations: According to Müller (1873/1883) of Germany, the nectar of the flowers attracts long-tongued bees, including honeybees, bumblebees, and Anthophorine bees (Anthophora spp.). Another visitor sucking nectar from the flowers was Bombylius major (Giant Bee Fly), which also occurs in North America.
Photographic Location: Along the bank of a drainage canal in Urbana, Illinois.
Comments: The most distinctive characteristic of Purple Dead Nettle is the purple tint of the young leaves at the apex of the stem. With the exception of Lamium amplexicaule (Henbit), other Lamium spp. (Dead Nettles) in Illinois are uncommon perennial plants with larger flowers (¾" or longer). Henbit is a sprawling weedy plant with sessile leaves near the flowers, while the same leaves of Purple Dead Nettle have short petioles. All of the species in this genus are native to Eurasia. The common name 'Dead Nettle' refers to the resemblance of the leaves to those members of the Nettle family with stinging hairs. However, Lamium spp. lack stinging hairs, therefore they are the safe, or 'dead,' nettles to be around. Another common name for Lamium purpureum is 'Red Dead Nettle.'