Verbena urticifolia var. leiocarpa L.M. Perry & Fernald
Family: Verbenaceae
white vervain
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Annual or perennial herb 40 cm - 1.5 m tall

Stem: erect, branching near base, nearly hairless to minutely stiff-haired. The flowering branches are very slender and loosely ascending to divergent.

Leaves: opposite, stalked, 5 - 20 cm long, more than 2 cm wide, egg-shaped and tapering to a pointed tip, coarsely toothed, densely velvet-haired beneath, with hairs to 0.3 mm long.

Inflorescence: a branched cluster of numerous spikes, each ascending spike less than 7 mm thick, with flowers being well separated along the spike.

Flowers: white, subtended by 0.5 - 1 mm long bracts that are egg-shaped with pointed tips and hairs along the margin. The calyx is 2 mm long and minutely hairy with triangular lobes, and the corolla is barely longer than the calyx and has blunt lobes.

Fruit: four nutlets surrounded by the persistent calyx but exposed at the top, each nutlet 1.5 mm long with a smooth and shiny flattened back.

Similar species: Verbena urticifolia var. urticifolia differs by its leaves that are hairless or have minute stiff hairs 1 - 1.3 mm long, its 2 - 2.3 mm long calyx with appressed hairs, and its 2 mm long nutlets with wrinkled backs.

Flowering: June to October

Habitat and ecology: Rare in ravine woods and low ground.

Occurence in the Chicago region: native

Etymology: Verbena is the Latin name for vervain. Urticifolia means nettle-leaved. Leiocarpa means "having smooth fruit."

Author: The Morton Arboretum