Wood betony, also called common lousewort, often is found in large colonies. The flowers are in dense terminal clusters on unbranched stalks, light yellow, sometimes tinged with pink or purple, 2-lipped, the upper much longer than the lower, curving over the stamens. Each flower is subtended by an oblong, leaflike bract. Blooms April–May. Leaves are pinnately lobed, fernlike. Basal and most stem leaves are on long petioles; the stem leaves are alternate. At least the upper part of the plants is hairy. In early spring, the emerging leaves have a beautiful wine-red color.
Similar species: Swamp wood betony or swamp lousewort (P. lanceolata) flowers in summer and fall, grows in swampy open meadows and limey soils, and is most common in the southeastern Ozarks; its stem leaves are usually opposite, and the upper part of the stem is not hairy.
Height: to 10 inches when flowering; growing taller later.
Statewide; absent from some southeastern counties.
Habitat and Conservation
Occurs in dry and open woodlands, prairies, shaded glades, bottomlands, streamsides, and wooded valleys; often in leached or acid soils.
Many plants in this genus are called “lousewort” from an antique belief that cattle would be plagued with lice if they ate these plants. There is something parasitic about this plant, however: It is a root parasite on other plants.
In addition to its taproot, wood betony sends out side roots that can attach to the roots of nearby plants such as grasses and tap nourishment from them. It can grow without host plants, however.