Dwarf Western Rosinweed

Calycadenia villosa occurs in Monterey and San Luis Obispo counties and is often localized. It is in the Center for Plant Conservation’s National Collection of Endangered Plants.

Plants 10–40 cm; self-incom-patible. Stems (± reddish distally) simple or branched (branches 1–4+ and ascending, or more numerous and spreading, rigid), hirsutulous-hispidulous, ± villous. Leaves (sometimes basal clusters persisting to flowering) mostly alternate, 2–5 cm, ± hispidulous (margins ± densely ciliate, especially proximally). Heads in ± spi-ciform arrays (1–3 per node). Peduncular bracts (crowded, closely investing, obscuring heads before flowering) lance-elliptic to linear (± flat distally), 3–10(–15) mm (hirsutulous, bristly and/or pectinate-fimbriate, deeply grooved proximally), apices (often ± reddish) rounded to truncate, tack-glands (0–)1 (terminal). Phyllaries (± reddish distally) 5–6 mm, abaxial faces hirsutulous, usually bristly, ± shaggy long-hairy near distal margins, tack-glands 0. Paleae 5–6 mm. Ray florets 1–4; corollas white to pinkish, tubes ca. 2 mm (papillate), laminae ca. 5 mm (central lobes much narrower than laterals, widest at bases, symmetric, laterals asymmetric, sinuses ¹/3–¹/2 laminae). Disc florets 5–15; corollas white to pinkish, 5–6 mm. Ray cypselae ca. 2.5 mm, smooth, densely appressed-hairy. Disc cypselae ca. 2.5 mm, appressed-hairy, especially on angles; pappi of ca. 10 lanceolate-aristate scales ca. 4–6 mm. 2n = 14.

Calycadenia villosa is an uncommon species of flowering plant in the family Asteraceae known by the common name dwarf western rosinweed. It is endemic to central California, where it is known from a limited distribution in the Central Coast Ranges in Monterey County and San Luis Obispo County, with a few populations in Santa Barbara and western Fresno Counties. There are perhaps 16 occurrences.

Calycadenia villosa is an annual herb producing a very hairy erect stem approaching 40 centimeters (16 inches) in height. The leaves are linear (long and narrow) and up to 5 centimeters (2 inches) long. The inflorescence is made up of clusters of flower heads surrounded by gland-tipped bracts. Each flower head is a hairless bunch of small disc florets and one to four white to pink ray florets. Each ray floret has three lobes, the middle lobe being narrowest. The fruit is an achene; those developing from disc florets bear a pappus of scales.