Piedmont Rhododendron

Size, growth and what to expect

Piedmont rhododendron grows slowly, so our growth estimator treats it as slow, about a foot a year. It grows 3 to 10 feet tall and 3 to 6 feet wide, dense and rounded, and it often spreads by rhizomes.

Trusses of 5 to 10 flowers open from April to June. Each flower is about 1.5 inches across, pink to white, with greenish spots on the upper petal. Bumble bees find it especially valuable, and the genus feeds a specialist bee, Andrena cornelli. The capsules ripen in September and October.

It grows wild from the Carolinas and Tennessee to Georgia and Alabama. Its home is woods and mountain balds, moist slopes, stream banks and rocky ridges. NatureServe ranks it imperiled in Alabama and imperiled to vulnerable in Tennessee.

How to grow Piedmont Rhododendron

Piedmont rhododendron grows best in part shade under a high canopy, and it takes deep shade. It can stand full sun in some places, but keep it out of windy sites. It wants a cool, moist, acid soil rich in organic matter that drains well. It will not stand dense clay, and its roots rot where water stands. Set plants 5 feet apart and keep them 3 feet from a wall. At its size it can go within 15 feet of overhead wires.

Saplings ship potted. Plant them in early spring or fall, in a hole three times as wide as the root ball and no deeper. Set the top of the ball a little above the soil to help it drain, and put the native soil back in. Mulch with pine needles or leaves, kept off the stems. The seed is dust-fine and needs light, with no chilling. Sow it in January on the surface of damp shredded sphagnum moss, uncovered, at room temperature in good light under a clear cover. Seedlings come up in one to three weeks.

Water weekly through the first two summers, since drought stress invites leaf spot, but do not overwater or feed it heavily. Deer damage it often, so cage young plants where deer are common. Prune, if at all, right after bloom, because next year's flower buds form by mid to late summer. Leaves that roll up on cold winter days unroll as the air warms, which is normal.

Piedmont rhododendron carries both male and female parts in each flower, but each flower sheds its pollen days before it is ready to receive pollen, so bees must carry it. Plant two or more seedlings from different parents for a fuller set of seed. Lace bugs, aphids and mites can mark the leaves. Phytophthora root rot takes plants in wet, heavy soil, and yellow leaves on a limy soil mean it needs more acid. Every part of the plant contains grayanotoxins, though the hazard is low.