Plants 0.1-10(-12) dm across. Leaves: petiole 0.2-0.6(-1) cm; blade 0.3-2 × 0.5-2.5(-3) cm. Involucral bracts 1-1.5(-3) × (1.5-)2-3(-3.5) mm. Flowers: perianth 0.9-1.2 mm; filaments 0.5-0.6 mm; anthers 0.2-0.3 mm. Achenes 1.2-1.5 mm. 2n = 28. Flowering Mar-Jul. Sandy to gravelly soils in shady places in grassland and chaparral communities, and in oak-pine or occasionally montane conifer woodland; 0-1600 m; Ariz., Calif., Nev., Utah; Mexico (Baja California). The only presumed Oregon collection of Pterostegia drymarioides (Tolmie s.n., GH) was gathered along the Columbia River sometime in the 1830s. The only collection reportedly from New Mexico (Parry et al. 1171, US) supposedly was found in the Rio Grande Valley in the 1850s during the United States-Mexico Boundary Survey. The species likely will be found in southern Oregon (not northern), but it is unlikely that it ever occurred in New Mexico. A problem is that this species is often difficult to notice, as the plants tend to be in the shade under shrubs. Specimens often are misidentified as Parietaria (Urticaceae)-See Flora of North America volume 3, pages 406-408.
FNA 2005, Wiggins 1964, Kearney and Peebles 1969
Duration: Annual Nativity: Native Lifeform: Forb/Herb General: Slender annual with stems branching from base, prostrate or scrambling 10-50 cm long, sparsely hirsute. Leaves: Opposite, on petiole 0.2-0.6 cm long, lower leaves fan shaped, 3-18 mm broad, often 2-lobed and minutely crenulate, narrowing to petiole, upper leaves orbicular or slightly wider than long, rarely notched, entire or crenulate. Flowers: Involucral bract 2-lobed, 15-2 mm long in flower, 2-3 mm in fruit, irregularly lobed; calyx lobes usually 6, rarely 5 , lanceolate, acute, finely and sparsely crispate-hirsutulous. Fruits: Three angled achene, 1 mm long, reddish or buff, smooth and shining. Ecology: Found on open or shaded slopes or among rocks below 3,500 ft (1067 m); flowers February-April Notes: Due to its preferred habitat, this species is often misidentified as Parietaria. They can be told apart by the leaf shape. Pay attention to the oblong leaves of Parietaria where the leaves in Pterostegia are fan-shaped. Ethnobotany: Unknown Etymology: Pterostegia is from pteron, wing and stegon or stege, meaning covering, referring to the winged bract, while drymarioides means like the genus Drymaria. Synonyms: None Editor: SBuckley, 2010