Photo: Gilles Ayotte, CC BY-SA 4.0 · Wikimedia Commons

Rhodora

Rhododendron canadense

Also called Canada rosebay, Azalea canadensis.

Rose-purple, two-lipped azalea flowers on bare twigs in May, lighting up the bogs and wet woods of the Northeast before the leaves.

Showy flowersTolerates wet soilWildlife valueRare

Type: Shrub
Mature height: 1–3 ft
USDA zones: 4–6
Growth rate: Slow
Sun: Full, Part
Soil moisture: Average, Wet
Grows wild in: The Appalachians, rocky ground, swamps and wet flats
Native range: 9 states, north to Maine, south to New Jersey and west to Pennsylvania
List all 9
Connecticut, Maine, Massachusetts, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island and Vermont
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Rhodora is the wild azalea of the Northeast's bogs, swamps and rocky summits, from Pennsylvania and New Jersey north through New England to Newfoundland and Labrador. Its flowers are unlike most azaleas, with three upper petals joined into a lip and two narrow lower ones spread apart. It is the one close relative of our pinkshell azalea, and Ralph Waldo Emerson named a poem for it. New York lists it as threatened, and New Jersey lists it as endangered. Plant it at the damp edge of a pond or bog garden in a cool garden, where its May flowers can be seen across the water.

Size, growth and what to expect

No source rates its growth, so our growth estimator treats it as slow, like our pinkshell azalea, about a foot a year. It is an erect, thinly branched shrub, rarely over 3 feet and at most 4, spreading by underground stems.

Clusters of 3 to 9 rose-purple flowers, rarely white, open on bare twigs before the leaves, from April and May in the south of its range to mid June in the north and on mountains. Each is about an inch across, with ten long stamens and little or no scent. Bumblebees and butterflies, among them the bog elfin, take its nectar, and it is a host plant of the Columbia silkmoth. The capsules split in late summer and fall, and the wind scatters the dust-fine seed.

It grows wild from northern New Jersey and Pennsylvania north through New York and New England to Ontario, Quebec and Newfoundland. Its home is bogs, swamps, wet woods, lake margins, thickets and barren rocky summits.

How to grow Rhodora

Rhodora grows in full sun or part shade and needs a cool climate. It wants a cold, wet, acid soil, peaty or rocky, that stays moist without standing in water. It is fairly hard to grow, since it needs steady moisture. Set plants 3 feet apart and keep them 2 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. Set the top of the ball at grade, put the native soil back in, and mulch with leaves or pine needles, kept off the stems. The seed is dust-fine and needs light but no chilling. Sow it in winter on the surface of damp peat under mist or a clear cover, uncovered, at room temperature. Seedlings come up in one to three weeks.

Water weekly through the first two summers, and never let the roots dry out. It spreads slowly by underground stems into a patch. Deer often damage azaleas, so cage it where deer are common. Prune, if at all, right after bloom.

Each flower carries both male and female parts, and bumblebees are its usual pollinators. Sources disagree on whether a native azalea sets seed with its own pollen, so plant two seedlings from different parents for seed. Azaleas are poisonous if eaten.

Heights and zones are typical ranges for the species in cultivation; local conditions and seed source shift them.

Sources (10)