Swamp Azalea

Size, growth and what to expect

No source rates swamp azalea's growth, so our growth estimator treats it as slow, like our other wild azaleas, about a foot a year. It usually grows 3 to 5 feet tall, less often 8, and 3 to 8 feet wide. In the wild it can reach 15 feet or more.

Clusters of 4 to 9 white or pale pink flowers open from May to July, after the leaves, one of the last native azaleas to flower. Each is about an inch and a quarter across, a narrow tube that flares into five lobes. The capsules follow from July to October. The leaves turn yellow, orange and purple in fall.

It grows wild from Maine and New Hampshire south to central Florida and west to Tennessee, Arkansas, Oklahoma and Texas. Its home is acid swamps, bogs, seepage slopes, pocosins, wet pine flatwoods and shrub balds, up to about 4,900 feet.

How to grow Swamp Azalea

Swamp azalea does best in part shade and takes some sun, but afternoon sun can scorch the leaves. It wants acid, humus-rich soil that stays moist or wet, and it stands periodic flooding, though its roots must not sit under water. Keep it clear of black walnut and butternut, whose roots release juglone, which can kill azaleas. Set plants 5 feet apart and keep them 4 feet from a wall. At its size it can go within 15 feet of overhead wires.

Saplings ship potted. Plant dormant plants in early spring or fall, in a hole three times as wide as the root ball and no deeper, and put the native soil back in. Mulch with wood chips, bark or pine needles, kept off the stems. The seed is dust-fine and needs light, with no chilling. Sow it in winter on the surface of damp milled sphagnum, uncovered, at room temperature under lights and a clear cover. Seedlings come up in one to three weeks.

Water weekly through the first two summers unless the ground stays damp, and never let the shallow roots dry out. Never hoe or dig over them. Rabbits seldom harm it, and where deer are common, cage young plants as for our other wild azaleas. Prune, if at all, right after bloom.

Each flower carries both male and female parts, and bees, moths and hummingbirds come to the flowers. Swamp azalea sets seed with its own pollen, so one plant bears alone, though bumblebees must carry the sticky pollen between flowers. It crosses at times with sweet azalea, and seed from a plant near other azaleas in bloom may give hybrids. Root rot troubles it less than most azaleas, though lace bugs, aphids and mites can mark the leaves. Every part of the plant is poisonous if eaten, and honey from its flowers can be too.