Rhododendron catawbiense

‍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.

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 prefers 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 evergreen Rhododendrons are highly toxic if ingested.

‘Grandiflorum’ is a medium dense cultivar with deep, slightly shiny, green foliage. Its long lasting, large lilac-purple flowers have matching filaments and ginger-brown spotted throats

'Boursault' is a dense, upright, variety. It has violet buds that open into lavender flowers with some reddish or pale brown spots. It will grow 6 feet tall in 10 years but eventually can grow to 10-15 feet tall.