Santa Cruz tarplant
Plants 10-50 cm; stems notably stipitate-glandular. Heads borne singly or in glomerules or spiciform-glomerulate arrays. Involucres ± globose. Phyllaries each bearing ± 25 gland-tipped processes and minutely sessile- or stipitate-glandular. Ray florets 8-16. Disc florets 40-90; anthers reddish to dark purple. 2n = 8. Flowering Jun-Nov. Grassy areas, clay soils; of conservation concern; 10-200 m; Calif. Holocarpha macradenia occurs on the coast from near Santa Cruz to central Monterey Bay area (most populations in the San Francisco Bay area are extirpated). Populations are reportedly highly interfertile; crosses to H. virgata have sometimes yielded moderately to highly fertile hybrids (the two species do not co-occur). J. Clausen (1951) and R. E. Palmer (1982) suggested that H. macradenia is most closely related to H. virgata; that hypothesis has been confirmed by molecular data (B. G. Baldwin, unpubl.).
This project made possible by National Science Foundation Award 1410069