Arboreum Rhododendron               rho-do-DEN-dron ar-BO-ree-um

• Broadleaf evergreen shrub or tree, forms vary from a many branched, bushy shrub to a spreading, rounded or columnar tree with a single stem, in the wild it may attain a height 40 ft (12 m), under cultivation it may reach 10 ft (3 m) high in 10 years.  Leaves are stiffly leathery, oblong-lanceolate to oblong-oblanceolate, 10-20 cm long and 3-6 cm wide, apex obtuse or acute, base tapered or rounded, upper suface dark or olive green, lower surface clad with a close, usually whitish indumentum.  Flowers are cup shaped, to about 5 cm long and wide, blood red is the typical color, darker markings on the lobes and nectar pouches at the base, 10 glabrous stamens; 15-20 flowers in tight clusters.
• 5^o F, early, 3/4/3 [quality rating of flower / foliage & plant / performance, based on a 1(poorest) to 5 (best) scale].
• There are several forma (f.), varietes (var.), and subspecies (ssp.) listed under R. arboretum, most of which are also classified (i.e., named) differently.  Some of these include:
  • var. album (syn. R. arboreum f. album; R. arboreum ssp. cinnamomeum var. album): white flowers with purple spots.
  • var. roseum (syn. R. arboreum f. roseum; R. arboreum ssp. cinnamomeum var. roseum): rose or deep pink flowers with darker spots.
  • ssp. cinnamomeum: (syn. R. arboreum ssp. cinnamomeum var. cinnamomeum): cinnimon indumentum on the underside of leaves, white flowers.
• Native to the Himalyas, one of the most common plants of the rhododendron forests.
• arboreum: tree-like.
• Federal Way, Washington: Rhododendron Species and Botanical Garden.