Orobanche valida subsp. howellii
Madroño 29: 98, fig. 1A–E. 1982.
Plants (6–) 10–20 cm, base often slightly enlarged. Bracts, bracteoles, and calyces densely glandular-pilose, hairs 0.2–0.4 mm. Corollas 14–16 (–18) mm; palatal folds puberulent; lips and tube densely glandular-pilose throughout, hairs 0.4–0.7 mm; filaments sparsely pilose at base, anthers pilose. 2n = 48.
Phenology: Flowering Jun–Sep.
Habitat: Rocky volcanic, serpentine slopes, open chaparral.
Elevation: 1200–1700 m.
Subspecies howellii is restricted to Glenn, Lake, Mendocino, Napa, and Tehama counties in the northern and central Coast Ranges, geographically disjunct from subsp. valida. The confirmed hosts are species of Garrya. Reports of Eriodictyon and Quercus as hosts need confirmation. Further research on this rare subspecies is warranted to establish its range and conservation status.