Culture
Winter hardy to USDA Zones 4-8 where it is best grown in acidic, humusy, organically rich, evenly moist, moisture-retentive but well-drained soils in part shade. Performs well with some morning sun but needs shady afternoon conditions. Tolerates close to full shade. Prefers cool summer temperatures. Roots must never be allowed to dry out. Acidify soils prior to planting and thereafter as needed. Plant in locations protected from strong winter winds. Do not site plants within or near the drip line of trees in the walnut family (most rhododendrons are sensitive to toxic juglones produced by roots of walnuts, butternuts, pecans and hickories). 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. All parts of this plant are highly toxic if ingested.
Noteworthy Characteristics
Rhododendron catawbiense, commonly called Catawba rhododendron or mountain rosebay, is a large, rounded to spreading, multi-stemmed, broadleaf evergreen shrub that typically grows to 6-10’ (rarely to 20’) tall. It is native to the eastern U.S. from Maryland to Kentucky south to Alabama and Georgia, with concentrations in alpine woodlands, rocky slopes and ridges in the Appalachian Mountains from Virginia to Georgia where it often forms dense thickets. Alternate, elliptic to oblong, glossy, dark green leaves (to 3-6” long). Funnel-shaped lavender-pink flowers have green to yellow-brown throat markings. Flowers bloom mid to late spring in compact showy terminal clusters (trusses), each containing 15-20 flowers. Flowers are followed by elongated dry seed capsules (each to 1/2 to 1” long) which mature in fall. Gray-brown bark develops fine scales with age. Provides shelter and nesting sites for birds and wildlife. Flowers are a nectar source for butterflies. This shrub is an important parent of a large number of frost-hardy hybrids.
Genus name comes from the Greek words rhodo meaning rose and dendron meaning tree. Transferred from the Greek name for Nerium oleander.
Specific epithet comes from the Catawba region of the Blue Ridge Mountains of eastern North America.
‘Roseum Elegans’ is a vigorous grower with good habit with large, glossy, dark green leaves. This large, dense, broadleaf evergreen rhododendron thrives in cooler regions. Its a popular cultivar valued for its large rounded clusters of rosy lavender flowers which can hold up to 20 attractive bell-shaped flowers with delicate reddish-brown dorsal spotting.
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 whiteflies. A healthy plant in the proper environment should have limited problems.
Uses
Shrub borders. Woodland gardens. Shady locations. Naturalized areas. Wood margins. Accent/specimen, groups or mass plantings.