This species is used as a parent in hybrids such as the P.J.M.Hybrids.

Common groups of hybrid Rhododendrons

'Girard' Hybrids: This large group of azaleas includes both deciduous and evergreen cultivars. They vary in flower color and winter hardiness.

'Knapp Hill' Hybrids: the result of crosssing several species of Rhododendron. A large group including 'Knapp Hill', 'Exbury', 'Slocock' and 'Ilam' Hybrids. These azaleas are deciduous. Flower color depends on the cultivar selected. Mildew can be a problem with this group. hardy zone 5-7.

'Northern Lights' Hybrids: developed at University of Minnesota. These hybrids were selected for excellent cold hardiness (to -30 degrees). These azaleas are deciduous. Flower color depends on cultivar selected.

'P.J.M.' Hybrids: a group of hybrids that are known for their compact size (3-6 ffet) and their flower color (shades of lavender pink to mauve). These rhododendrons are evergreen, with the foliage taking on a purplish cast in winter. Hardy zone 5 to 7.

Bacterial Disease

• Crown Gall (Agrobacterium tumefaciens)

Environmental Damage

• Drought
• Drowning and Edema
• Winter Injury

Fungal Disease

• Dieback/Canker (Nectria spp., Phomopsis spp., Botryosphaeria spp., Tubercularia spp., Phytophthora spp.)
• Gray Mold [Trees and Shrubs] (Botrytis cinerea and other species)
• Phomopsis Gall (Phomopsis spp.)
• Phytophthora Canker, Basal Rot, & Root Rot [Shrubs and Trees] (Phytophthora spp. [water molds])
• Wood Rots and Decays (Many genus and species involved)

Herbicide Injury

• Plant Growth Regulator (PGR) Herbicide Injury

Insect Damage

• Black Vine Weevil (Otiorhynchus sulcatus)
• Thrips (Many)

Additional pests and problems that may affect this plant:

Leaf spots, powdery mildew, scale, thrips, whitefly and other pests are possible problems.

Alkaline soils will lead to chlorosis (yellowing ) of the leaves; winter sun and wind can be damaging to the evergreen foliage.