Oregon Woollyheads

Psilocarphus oregonus occurs from west-central California through most of Oregon to southeastern Washington, western Idaho, and northern Nevada. Relatively narrow-leaved, montane forms of P. tenellus account for reports of P. oregonus from the southern Sierra Nevada to Baja California; further study may show these to be intermediates between the two taxa.

A malformed plant collected in Merced County, California, appears to have been a sterile hybrid between P. oregonus and Hesperevax caulescens (J. D. Morefield 1992c).

Plants silvery to whitish, densely sericeous to somewhat lanuginose. Stems (1–)2–10, ascending to ± prostrate; proximal internode lengths mostly 0.5–1.5(–2) times leaf lengths. Capitular leaves ± erect, appressed to heads, linear to narrowly oblanceolate, widest in distal ²/3, longest 12–20 mm, lengths mostly 6–12 times widths, (3–)3.5–5 times head heights. Heads ± spheric, largest 4–6 mm. Receptacles unlobed. Pistillate paleae individually visible through indument, longest mostly 1.5–2.7 mm. Staminate corollas 0.7–1.4 mm, lobes mostly 4. Cypselae narrowly ± cylindric, terete, 0.6–1.2 mm.

Psilocarphus oregonus has a bioregional distribution that includes the northern California Floristic Province; Modoc Plateau, Oregon; Washington; Idaho; and possibly in Baja California. Elevations of occurrence are from ten to 1500 meters. This plant occurs in vernal pools and other wet grassland areas, with prototypical locations including the Jepson Prairie and Lake Henessey grassland perimeter in Calfornia.

This species, known by the common name Oregon woollyheads is generally silky-tomentose. There are typically several stems arising from the base and spreading. Uppermost leaves are linear to narrowly oblanceolate, with the longest 12 to 20 millimeters. The small inflorescences have their largest heads of characteristic size four to six millimeters.

Psilocarphus oregonus is a species of flowering plant in the family Asteraceae known by the common names Oregon woollyheads and Oregon woolly marbles. It is native to western North America from Washington and Idaho to Baja California, where it grows in seasonally wet habitat, such as vernal pools.