Rhododendron macrophyllum

D. Don ex G. Don

Gen. Hist. 3: 843. 1834 ,.

Common names: California rhododendron
Endemic
Synonyms: Rhododendron californicum Hooker
Treatment appears in FNA Volume 8. Treatment on page 462. Mentioned on page 456.

Shrubs or trees, to 5 m, sometimes rhizomatous. Stems: bark smooth to vertically furrowed, shredding; twigs with basally branched, crisped/matted, eglandular hairs, very quickly glabrate. Leaves persistent; petiole glabrous; blade elliptic to slightly ovate or obovate, (6–) 8.5–14 (–20) × 2.5–5.5 (–7.5) cm, thick, coriaceous, margins entire, plane to revolute, glabrous, apex acute to obtuse or slightly acuminate, surfaces scattered eglandular-hairy (hairs branched basally, crisped, very quickly deciduous), abaxial surface ± smooth. Floral bud-scales multicellular eglandular-hairy (hairs branched basally), and unicellular-hairy (hairs short-to-elongate) abaxially, margins eglandular-hairy (hairs branched). Inflorescences 10–20-flowered; bracts similar to bud-scales. Pedicels 30–60 mm, glabrous. Flowers opening after development of leaves (of flowering shoots), erect to horizontal, fragrant; calyx lobes 1–1.5 mm, glabrous, except margins eglandular and stipitate-glandular-hairy; corolla white to pink or rose-purple, with yellowish green spots on upper lobe, broadly campanulate, 24–48 mm, outer surface glabrous, petals connate, lobes 14–30 mm, tube gradually expanding into lobes, 10–23 mm; stamens 10, included, ± unequal, 16–37 mm. Capsules borne on erect pedicels, 13–25 × 4–7 mm, eglandular-hairy (hairs ferruginous, branched or unbranched) and, often, stipitate-glandular-hairy. Seeds without distinct tails, flattened portion of testa well developed at each end; testa expanded, dorsiventrally flattened, loose. 2n = 26.


Phenology: Flowering spring–summer.
Habitat: Forest and forest margins, thickets
Elevation: 50-1600 m

Distribution

V8 904-distribution-map.gif

B.C., Calif., Oreg., Wash.

Discussion

Rhododendron macrophyllum, R. maximum, and R. catawbiense represent subg. Hymenanthes (Blume) K. Koch in North America; the subgenus is represented by hundreds of species in temperate eastern Asia and is characterized by its branched, eglandular hairs (D. F. Chamberlain 1982). These showy plants are frequently used as ornamentals.

Selected References

None.

Lower Taxa

None.

... more about "Rhododendron macrophyllum"
Walter S. Judd +  and Kathleen A. Kron +
D. Don ex G. Don +
smooth +  and vertically furrowed +
not flaky +
14 cm140 mm <br />0.14 m <br /> (20 cm200 mm <br />0.2 m <br />) +
5.5 cm55 mm <br />0.055 m <br /> (7.5 cm75 mm <br />0.075 m <br />) +
8.5 cm85 mm <br />0.085 m <br /> (14 cm140 mm <br />0.14 m <br />) +
elliptic;slightly ovate or obovate +
coriaceous +
thick;2.5cm;5.5cm +
scale-like +
stipitate-glandular-hairy +  and glabrous +
0.1 cm1 mm <br />0.001 m <br /> (0.15 cm1.5 mm <br />0.0015 m <br />) +
1.3 cm13 mm <br />0.013 m <br /> (2.5 cm25 mm <br />0.025 m <br />) +
stipitate-glandular-hairy +  and eglandular-hairy +
0.4 cm4 mm <br />0.004 m <br /> (0.7 cm7 mm <br />0.007 m <br />) +
California rhododendron +
white +  and pink or rose-purple +
rotate to crateriform campanulate cylindric globose or urceolate +
2.4 cm24 mm <br />0.024 m <br /> (4.8 cm48 mm <br />0.048 m <br />) +
B.C. +, Calif. +, Oreg. +  and Wash. +
50-1600 m +
undifferentiated +
fusiform +
unicellular-hairy +  and eglandular-hairy +
erect;horizontal +
fragrant +
pendulous +  and erect +
usually ovoid;cylindric +
Forest and forest margins, thickets +
eglandular +  and branched +
terminal +  and axillary +
persistent +
14mm +  and 30mm +
eglandular-hairy +  and glabrous +
plane;revolute +
parietal +, axile +  and placentation +
tenuinucellate +  and unitegmic +
3 cm30 mm <br />0.03 m <br /> (6 cm60 mm <br />0.06 m <br />) +
scale-like +
reduced +
not sticky +
Flowering spring–summer. +
4-5-carpellate +
distinct +
tailed +, flattened-ellipsoidal +  and fusiform +
yellowish green +
unequal +
procumbent +  and prostrate +
creeping +  and sprawling +
peltate +  and capitate +
straight +
eglandular-hairy +
Rhododendron californicum +
distinct +
Rhododendron macrophyllum +
Rhododendron +
species +
flattened +
expanded +
expanding +
1 cm10 mm <br />0.01 m <br /> (2.3 cm23 mm <br />0.023 m <br />) +
evergreen +, deciduous +  and perennial +
tree +  and shrub +
heterotrophic +, autotrophic +  and mycotrophic +