Culture
Best grown in acidic, humusy, organically rich, medium moisture, moisture-retentive but well-drained soils in part shade. Prefers a sun dappled or high open shade. Tolerates a fair amount of sun in cool northern summers, but leaves may scorch in hot afternoon sun in the St. Louis area. 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 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. Acidify soils as needed. This species reportedly tolerates more neutral soils than most azaleas. Clip off spent flower clusters immediately after bloom as practicable.
Noteworthy Characteristics
Rhododendron schlippenbachii is an upright, rounded, deciduous azalea that is native to Korea, Manchuria and Japan. It typically grows to 4-6' tall (sometimes to as much as 15' tall). Funnel-shaped flowers (3 1/2” across) are white tinged with pink. Flowers are fragrant. Flowers bloom in clusters at the branch ends in April-May as the leaves emerge. Obovate to rhombic, dark green leaves (to 2-5” long) turn attractive shades of red, orange and yellow 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 honors Baron Alexander von Schlippenback, Russian naval officer, who reportedly collected the plant in Korea in 1854.
Problems
Rhododendrons and azaleas 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 and shade gardens. Also effective in foundation plantings or as a hedge.