Culture
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 locations protected from strong winter winds. Avoid warm sunny southern exposures where plants may flower/leaf out too early and suffer frost damage. 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 heavy clay soils such as those present in much of the St. Louis area. 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 immediately after bloom as practicable.
Noteworthy Characteristics
Rhododendron mucronulatum, commonly called Korean rhododendron is noted for its unusual (for rhododendrons) deciduous habit and for its early spring flowering period. It is native to Korea, Japan and northern China. It is a dense, upright, deciduous shrub which typically grows to a mature height of 4-8' tall and as wide. Flowers bloom in clusters at the branch tips in early spring (late March to early April in St. Louis) before the foliage emerges. This is perhaps the earliest blooming of the many species of cultivated rhododendrons. Elliptic, medium green leaves (to 3" long) are, as the species name suggests, mucronate (have sharp, pointed tips). Leaves turn interesting shades of yellow and red in fall.
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 with sharp, pointed tips for the leaves.
'Cornell Pink' features clear pink flowers, with no hints of purple or lavender.
Problems
Korean rhododendrons bloom so early in spring that they are susceptible to frost damage to both flowers/buds and emerging foliage, particularly if plants are sited in sunny locations. Rhododendrons are generally susceptible to many disease and insect 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. Chlorosis may occur in high pH soils. Notwithstanding the foregoing, a healthy plant in the proper environment with proper care should have limited problems.
Uses
Mass, group or specimen for shrub borders, mixed borders, woodland gardens and shade gardens. Also effective in foundation plantings and as a specimen around the home.