Culture
Best grown in acidic, organically rich, humusy, medium moisture, moisture-retentive but well-drained soils in part shade. Prefers a sun dappled or high open shade. Morning sun with afternoon shade is also acceptable. 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 winds. Plants perform well on north or east facing slopes. Do not site plants within or near the drip line of trees in the walnut family (most rhododendrons/azaleas are sensitive to toxic juglones produced by roots of walnuts, butternuts, pecans and hickories). Good soil drainage is essential (plants do not 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 (plants generally like soil pH in the range of 5.0 to 5.5). Add sulfur or iron sulfate to soils to lower the pH. Add limestone or lime to soils to raise the pH. Clip off spent flower clusters immediately after bloom as practicable.
Noteworthy Characteristics
Kurume hybrid azaleas were originally discovered in the mountains of Japan at least 300 years ago as naturally occurring hybrids originating from crosses between R. kiusianum, R. kaempferi, R. sataense and R. obtusum (group). Kurumes were first introduced into the U.S. around 1915.
Genus name comes from the Greek words rhodo meaning rose and dendron meaning tree. Transferred from the Greek name for Nerium oleander.
'Amoenum' is an evergreen to semi-evergreen azalea (Kurume hybrid) which features an early to mid-spring bloom (April in St. Louis) of small, bright magenta flowers on stems clad with small, glossy, dark green leaves. It typically grows over time to 1-3' tall, but infrequently to as much as 6' tall.
Problems
Rhododendrons and azaleas are susceptible to many insect and disease problems. Insect pests include aphids, borers, lacebugs, caterpillars, leafhoppers, mealybugs, nematodes, scale, thrips and whitefly. Mites may also appear. Disease pests include blights, canker, crown rot, leaf gall, root rot, leaf spot, rust and powdery mildew. Chlorosis (leaves turn yellow) often indicates an iron deficiency in the soil that is often caused when the soil pH becomes too high. 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. Woodland margins. Often used for bonsai.