Luxuriant and bold, rosebay rhododendron (Rhododendron maximum) is a stunning broad-leaved evergreen for a large garden or naturalized in the woodland landscape. This multi-stemmed, upright spreading shrub typically grows 8 to 15 feet tall… but can reach to 30 feet in Appalachian Mountains where it is native. In early summer, mature branches produce large floral clusters or trusses, with up to 25 white to pale pink flowers. Leaves are 4 – 8 inches long, (USDA hardiness zones 3-7).

Site selection is very important. Rosebay rhododendrons thrive in acidic, humus -rich, moist, well-drained soils and in part shade. These large shrubs tolerate almost full shade. In zone 7 rosebay rhododendrons thrive in cooler mountain landscapes and languish on urban sites. Roots prefer to be cool in the hot summer periods; leaves may wilt and turn off color during periods of hot dry weather.

Good soil drainage is an absolute must. Poor drainage or “wet feet” inevitably leads to root rot problems such as Pythium, Phytophthora and Rhizoctonia soil fungi. On heavy clay sites, plant rosebay rhododendrons on sloping ground or in raised beds/plantings. Rhododendrons also benefit by mulching with wood chips, bark or pine needles which aid in soil moisture retention and keeping the ground cool.

Feed with an acidifying fertilizer such as Hollytone™ or water-soluble product like Miracid™ soils according to package directions. Plant these tall evergreen shrubs in a sheltered location away from strong drying wintry winds.

All parts of this plant are highly toxic if ingested. It partners well with native woodland favorites such as Christmas fern (Polystichum acrostichoides), pinxterbloom azalea (Rhododendron periclymenoides), columbine (Aquilegia canadensis), foamflower (Tiarella cordifolia), Hairy alumroot (Heuchera villosa), bellworts (Uvularia spp.), and wild ginger (Asarum canadense).

Three of the most common cultivars of Rosebay rhododendron include:

Var. album: White flowers

Var. purpureum: Deep pink to purple flowers

Var. roseum: Light pink flowers on reddish stems

Rosebay Rhododendrons are not commonly sold at box stores. However, plants are available at many Northeast and Midwest full-service garden centers as well as at e-commerce nurseries in USDA hardiness zones 3-7.