Biennial or perennial herb to 1 m tall Leaves
: alternate, stalkless to short-stalked, 4 - 10 cm long, 1.5 - 2 cm wide, usually smaller near top of plant, narrow and inversely egg-shaped with a pointed to rounded tip, coarsely toothed, covered with stinging barbed hairs. Flowers
: borne near branch tips, white to cream, with 100 to 200 stamens, opening in afternoon, closing near sunset. The ten petals are 2 - 5 cm long, narrow and inversely egg-shaped, and usually do not overlap when open. Fruit
: a cylindric capsule, 2 - 3 cm long, 8 - 10 mm wide, opening at the tip. The seeds are flat with well-developed wings. Stems
: single to few, erect, often branching on upper half, yellowish to whitish.
Similar species: Mentzelia decapetala is a coarser plant with longer petals (4 - 7 cm) that tend to overlap and flowers that remain open until around midnight.
Flowering: July to August
Habitat and ecology: Introduced from farther west, this species grows near railroads.
Occurence in the Chicago region: non-native
Etymology: Mentzelia is named after German botanist Christian Mentzel (1622 - 1701). Nuda means naked.
Author: The Morton Arboretum