Rhododendron viscosum var. glaucum

The glaucous swamp azalea is a native deciduous shrub of the wetland South and the eastern seaboard, a blue-leaved form of Rhododendron viscosum, the widespread swamp azalea that ranges from the Gulf Coast north into New England. The variety glaucum sets the plant apart with foliage washed in a soft blue-green, most striking on the leaf undersides, which flash pale as a breeze turns them. Where many shrubs falter, this azalea thrives in the consistently moist, even boggy ground of swamps, marshes, and stream banks.

Rhododendron viscosum entered the botanical record early, described in the first half of the eighteenth century as European gardeners and naturalists took stock of the rich American azalea flora, and the swamp azalea has been part of cultivated horticulture ever since. The species carries several old common names, clammy azalea and swamp honeysuckle among them, each pointing at a real trait: the sticky, glandular hairs that coat the flower tube, and the sweet, honeysuckle-like scent that gives the shrub much of the garden value.

The flowers open in late spring and early summer, after most azaleas have finished, in clusters of narrow white to blush trumpets clothed in glistening sticky hairs and carrying a powerful sweet, clove-like perfume. Bees, butterflies, and hovering sphinx moths work the late bloom, drawn by scent across surprising distances. As with every azalea, the whole plant carries grayanotoxins and is poisonous if eaten, so the swamp azalea is grown for fragrance and beauty rather than for any use, and is best sited away from where livestock might browse.

Few shrubs solve a wet, acidic, shaded problem as gracefully. Plant the glaucous swamp azalea at a pond or stream edge, in a rain garden, in a boggy low spot, or along a moist woodland border, where the roots find the standing moisture the plant welcomes and the blue foliage cools the greens around the shrub. Full sun is tolerated where the soil stays reliably wet, though morning sun with afternoon shade suits warmer gardens best. Pair with clethra, itea, sweetbay magnolia, and native ferns, and site where the summer fragrance can be caught on the air near a path or a seat.