Mentzelia albescens (Gillies ex Arn.) Benth. & Hook. f. ex Griseb.
Wavyleaf Blazing Star
CC = *
CW = 5
MOC = 5
Family - Loasaceae
Habit - Biennial or perennial forb with a thick taproot.
Stem - Erect, to 60 cm, brittle, whitish in color, densely pubescent with barbed hairs.
Leaves - Alternate, simple, short-petiolate. Blades 3-15 cm long, 1.0-2.5 cm wide, linear to ovate-lanceolate, rounded to bluntly or sharply pointed at the tip, the margins coarsely and broadly toothed or lobed, densely pubescent with barbed hairs.
Inflorescences - Terminal solitary flowers, or small terminal clusters. Flowers subtended by 1-3 narrow entire bracts.
Flowers - Actinomorphic, perfect. Hypanthium 10-20 mm long. Sepals 5, 3-6 mm long, linear, withered but persistent at fruiting. Petals apparently 10 (including 5 petaloid staminodes), 6-8 mm long, 1-2 mm wide, lanceolate to spatulate, narrowed to a sharply pointed tip, lemon yellow to pale yellow. Stamens to 30-40, the outer 5 modified into petaloid staminodes (indistinguishable from the petals). Carpels 3, fused. Ovary inferior, with 1 locule. Flowers closed during the day, opening at dusk.
Fruits - Cylindrical capsules 18-28 mm long, 6-7 mm in diameter, densely pubescent externally with barbed hairs. Seeds numerous, 2-3 mm in diameter, positioned horizontally, flattened, winged, the seed coat minutely pebbled, tan.
Flowering - May - August.
Habitat - Mine tailings, railroads, sandy disturbed areas.
Origin - Native to south-central U.S. and southward.
Other info. - This is one of only three Missouri representatives of a fascinating genus. The species is uncommon in the state, thus far reported from only five counties. It is scarcely more common elsewhere in the U.S., being known from only a few additional counties in Oklahoma and Texas. It is distinguished from the other two Missouri members of the genus by having yellow flowers which appear to have 10 petals (five of these are actually petal-like staminodes). The flowers are normally closed during the daytime, opening at dusk. This suggests pollination by moths. The images above showing closed and open flowers were taken a few hours apart on the same day.
Photographs taken near Pacific, St. Louis County, MO, 8-11-2010 and 7-13-2012 (SRTurner).