Culture
Winter hardy to USDA Zones 7-9 where it is best grown in acidic, humusy, organically rich, moisture-retentive but well-drained soils in part shade. Prefers a sun-dappled shade. Foliage may scorch in full sun. Acidify soils prior to planting and thereafter as needed. Plant in a location protected from strong winter winds. Good soil drainage is essential (doesn’t like “wet feet”). Poor drainage inevitably leads to root rot, therefore raised beds/plantings should be considered in areas with heavy clay soils. Shallow, fibrous root systems (do not cultivate around plants) will benefit greatly from a mulch (e.g., wood chips, bark or pine needles) to help retain moisture and stabilize soil temperatures. Roots must never be allowed to dry out. Clip off spent flower clusters as practicable immediately after bloom.
Noteworthy Characteristics
Rhododendron lanatum, commonly known as woolly rhododendron, is a compact, small-leaved, evergreen rhododendron that is native to coniferous forests, rhododendron thickets, and mountain slopes in the eastern Himalayas, primarily in Bhutan, Sikkim and Arunachal Pradesh at elevations from 10,000’ to 14,500’. It typically matures over time to 3-10’ tall and as wide.
As suggested by the common name, this rhododendron is particularly noted for having densely white to tawny, woolly-velvet young shoots and leaf stalks plus dark green leaves which are covered when young with a reddish indumentum.
Evergreen, leathery, elliptic to obovate or oblong-obovate, mature leaves (each to 4” long and 1 3/4” wide) have obtuse to broad wedge-shaped bases, curled margins and blunt to rounded tips. Mature leaves are dark green above but woolly, white-rufous beneath. Broad, bell-shaped, 5-petaled, maroon-spotted, sulfur-yellow flowers bloom in May in racemose-umbellate clusters, each containing 5 to 10-flowers. Flowers give way to seed capsules which mature in August.
Rhododendron flinckii and Rhododendron luciferum are considered by some experts to be synonyms with the within species, but other experts believe they are distinct species.
Genus name comes from the Greek words rhodo meaning rose and dendron meaning tree. Transferred from the Greek name for Nerium oleander.
Specific epithet means woolly for the woolly young shoots and leaves.
Problems
Rhododendrons are susceptible to many insect and disease problems, including but not limited to canker, crown rot, root rot, leaf spot, rust, powdery mildew, aphids, borers, lacebugs, leafhoppers, mealybugs, mites, nematodes, scale, thrips and whitefly. A healthy plant in the proper environment with proper care should have limited problems, however.
Uses
Mass, group or specimen. Shrub borders, mixed borders, woodland gardens, woodland margins, and shade gardens. Informal hedge. Also effective in foundation plantings and as a specimen around the home.