Petrophytum hendersonii

(Canby) Rydberg

in N. L. Britton et al., N. Amer. Fl. 22: 253. 1908.

Common names: Olympic mountain rockmat
Endemic
Basionym: Eriogynia hendersonii Canby Bot. Gaz. 16: 236. 1891 (as hendersoni)
Synonyms: Luetkea hendersonii (Canby) Greene Spiraea hendersonii (Canby) Piper
Treatment appears in FNA Volume 9. Treatment on page 412. Mentioned on page 411, 413.

Shrubs, 2–9 dm diam. Stems decumbent to ascending, 1–10 cm, internodes 0.5–1.5 cm. Leaves: blade narrowly obtrullate, sometimes oblanceolate to spatulate-obovate, 1–2(–3) × 0.2–0.6 cm, palmately 3-veined, venation visible through hairs, apex acute, abaxial surface sparsely strigose, pilose to pilose-sericeous, sometimes glabrate, sparsely strigose along veins. Panicles densely racemose, 2–5 × 1–2 cm, sparsely sericeous; bracts linear, 2–4(–6) mm, pilose. Pedicels 2–5 mm; bracteoles 1, rarely extending to base of sepals. Flowers 3–5 mm diam.; hypanthium 0.5–1 mm, sparsely pilose; sepals reflexed, oblong to obtuse, 1–1.5 mm, margins ciliate, abaxial surface sparsely pilose; petals oval, oblong, or obovate, 2–2.5 mm, apex obtuse, sometimes 2-lobate; stamens 25–40, lengths 1–1.3 times petals (2 times sepals); carpels (4–)5(–6), abaxially connate. Follicles 1.5–2 mm. 2n = 18.


Phenology: Flowering Jul–Sep.
Habitat: Rock outcrops, cliffs, talus slopes
Elevation: 1000–2300 m

Discussion

Petrophytum hendersonii is known only from the Olympic Mountains of northwestern Washington.

Selected References

None.

Lower Taxa

None.