Rhododendron calendulaceum, or flame azalea, is an upright, loosely branched deciduous shrub that typically matures to 4-8' (infrequently to 10-15’) tall and to 8-10’ wide, though like all native azaleas, it takes a while to get there. It is native primarily to woodland slopes and mountain balds in the Appalachian Mountains from Pennsylvania to Georgia. It produces funnel-shaped, usually non-fragrant flowers (2” diameter) bloom in loose trusses (5-10 flowers per truss) in May-June. The flowers have exserted (protruding) showy stamens. Variable flower color ranges from yellow to orange to red. Medium green leaves (1-3” long) are elliptic to obovate with yellow-red fall color.
This beautiful Azalea forms striking displays on some of the grassy balds of the southern Appalachians. A wide variation of color forms occurs, from all shades of yellow to orange-yellow and scarlet. The flowers appear before or with the new leaves. This species is extensively planted as an ornamental. Like most members of the heath family, it does best in acid soil. This species is an important parent of many deciduous azalea hybrids.
Best grown in acidic, light, sandy, well-drained soils in part shade. Tolerates well-drained humusy loams. It does not prosper in areas with high summer temperatures, and is not recommended for planting south off USDA Zone 7. Prefers a sun dappled shade or high open part shade. The foliage may scorch in full sun unless soils are kept uniformly moist. Consistent moisture is best, but soils must drain well (doesn’t like “wet feet”). Poor drainage inevitably leads to root rot, therefore raised beds/plantings should be considered in heavy clay soils. Roots should not be allowed to dry out. Acidify soils prior to planting and thereafter as needed. This shrub benefits from being planted in a location protected from strong winter winds. The shallow, fibrous root systems (do not cultivate around shrubs) will benefit from a good mulch (wood chips, bark or pine needles) for retention of moisture, stabilization of soil temperatures and winter protection, but not too thick. Clip off spent flower clusters after bloom as practicable.
Adapted From: Missouri Botanic Garden
We have a fair number of strong red genotypes.