Mentzelia sp.
Family: Loasaceae – Loasa Family
Mentzelia is the only genus of this family represented at Arches National Park. Many species in this genus are difficult to place with certainty because of the variability of plant size, leaf size, flower size and capsule size and shape.
Mentzelia albicaulis (Whitestem blazing star): Annual herbs; 3.9” to 1.3' (1 to 4 dm) tall; white or greenish-white stems
Mentzelia multiflora (Desert blazing star; Desert stickleaf): Perennial herbs from a taproot; 16” to 2.6' (4 to 8 dm) tall
Mentzelia pterosperma (Wingseed stickleaf): Perennial, biennial herbs, or flowering the first year; 2” to 1' (0.5 to 3 dm) tall; stems white with stiff coarse hairs
Mentzelia pumila ( Wyoming stickleaf): Biennial or short-lived perennial herbs from a stout taproot; whitish stems; 7.9” to 1.97' (2 to 6 dm) tall
Leaves: Mentzelia albicaulis: alternate; simple; lower leaves 1.2” to 5.9” (3 to 15 cm) long, entire, lobed or pinnatifid; upper leaves lance-shaped or linear, lobed or pinnatifid
Mentzelia multiflora: alternate; simple, can be lobed or toothed or pinnatifid; rough vegetation with rough, hooked, or even stinging hairs, hairy leaves; leaves are sticky, sand often sticks to their surfaces; lower leaves 1” to 4.8” (2.5 to 12 cm) long
Mentzelia pterosperma: alternate; simple; basal rosette leaves 1.2” to 2.9” (3 to 7.4 cm) long, 0.4” to 0.8” (10 to 20 mm) wide; leaves also along stems; hairy
Mentzelia pumila: alternate; simple; 3.3” to 7.9” (8.5 to 20 cm) long
Flowers: Mentzelia albicaulis: inflorescence with 1 to 3 flowers; 5 petals, 0.08” to 0.35” (2 to 9 mm) long; numerous stamens
Mentzelia multiflora: inflorescence with 1 to 3 flowers; 10 distinct yellow petals (the inner 5 somewhat shorter and narrower), petals 0.35” to 0.8” (9 to 20 mm) long, 0.24” to 0.32” (6 to 8 mm) wide, (described as 5 proper petals with 5 alternating petaloid staminodes in Intermountain Flora, Vascular Plants of the Intermountain West, U.S.A.); 4 to 5 sepals; numerous stamens which can be petaloid (can be as many as 200 stamens); 1 style
Mentzelia pterosperma: 10 yellow petals, 0.35” to 0.8” (9 to 20 mm) long, 0.16” to 0.3” (4 to 8 mm) wide, (described as 5 proper petals with 5 alternating petaloid staminodes in Intermountain Flora, Vascular Plants of the Intermountain West, U.S.A.); numerous stamens; outer stamens petaloid, 0.2” to 0.3” (5 to 8 mm) wide
Mentzelia pumila: inflorescence with 1 to 3 flowers; 10 yellow yellow or golden petals, often with a darker, orange to red-brown area at the base, 0.35” to 0.6” (9 to 15 mm) long, (described as 5 proper petals with 5 alternating petaloid staminodes in Intermountain Flora, Vascular Plants of the Intermountain West, U.S.A.); numerous stamens; outer stamens are petaloid, 0.6” to 0.8” (15 to 20 mm) long
Pollinators: some Mentzelia species are pollinated by bees
Fruits: capsule
Blooms in Arches National Park: April, May, June, July, August, September, October
Habitat in Arches National Park: desert shrub communities
Location seen: park road mile 0 to 2.5, park road mile 8, around Visitor Center buildings
Other: The genus name, “Mentzelia”, honors Christian Mentzel (1622-1701), a German botanist. The species name, “albicaulis”, means “white-stemmed”; the species name, “multiflora”, means “many flowers” referring to the quantity of flowers; the species name, “pterosperma”, means “having winged seeds”; and the species name, “pumila”, means “dwarf”.
