Evergreen or deciduous shrubs or small trees. Twigs terete; pith small, roundish, continuous. Buds solitary, sessile, the upper ovoid with 6 or more ciliate scales and the flower-buds usually much enlarged, the lower successively smaller. Leaf-scars alternate, shield-shaped or the lowest linear; bundle-trace 1 or 3 or many; stipule-scars none. Fruit a dry capsule, often present in winter. The deciduous species have been placed by some authors in the genus Azalea L.
Fig. 242. Rhododendron maximum.
Fig. 243. Rhododendron catawbiense.
b. Leaves elongate-oblanceolate, the base acute
b. Leaves broadly elliptical, the base rounded
b. Buds essentially glabrous
c. Twigs entirely glabrous
c. Twigs usually bearing sparse long hairs
*Mr. E. L. Manigaulthas assisted materially in the preparation of this key.
Fig. 244. Rhododendron canadense.
Fig. 245. Rhododendron calendulaceum.
Fig. 246. Rhododendron nudiflorum.
Fig. 247. Rhododendron roseum.
Fig. 248. Rhododendron viscosum.
Fig. 249. Rhododendron arborescens.
d. Buds brown
d. Buds rosy
c. Low shrub to lm.high
c. Much taller shrubs
d. Twigs reddish
d. Twigs buff or gray
e. Twigs tomentulose, at least near the tip
e. Twigs sparsely strigose-hirsute
f.Pedicels glandless or nearly so
f. Pedicels copiously glandular
1. R. maximum L. Rhododendron. Great Laurel. Large evergreen shrub or small tree to 12 m. high, the young branch-lets pubescent; leaves 10-20 cm. long, thick, acute at both ends. Moist woods, mostly in the mountains, Georgia to West Virginia and Nova Scotia (Fig. 242).
2. R. catawbiense Michx. Mountain Rose Bay. Spreading evergreen shrub or small tree 2-6 m. high; leaves oval or oblong, rounded at both ends, 5-15 cm. long. Rocky slopes, in the mountains, Georgia and Alabama north to West Virginia (Fig. 243).
3. R. canadense (L.) Torr. Rhodora. Shrub to 1 m. high,with strongly ascending branches. Bogs and barrens, Newfoundland to Quebec, south to Pennsylvania (Fig. 244).
4. R. calendulaceum (Michx.) Torr. Flame Azalea. Yellow Honeysuckle. Deciduous shrub to 3 m. high, the twigs usually tomentulose, at least near the tips, leaf buds brown, glabrous except for ciliate scales, the flower buds greenish; capsule linear-oblong, more or less pubescent, 1.5-2 cm. long. Open woods, mostly in the mountains, Georgia and Alabama, north to Pennsylvania and Ohio (Fig. 245).
5. R. nudiflorum (L.) Torr. Pink Azalea. Pink Honeysuckle. Deciduous shrub to 2 m. high or sometimes taller; twigs buff or gray, sparsely long-hairy or glabrate; buds glabrous, glandular or puberulous; capsules 1-2 cm. long with ascending long hairs, not glandular. Woods, South Carolina and Tennessee to Massachusetts, New York, and Ohio (Fig. 246).
6. R. roseum (Loisel.) Rehd. Mountain Azalea. Hoary Azalea. A deciduous branching shrub 1-5 m. high with buff or gray finely pubescent twigs; buds puberulous; capsules glandular, 1. 2-1. 8 cm. long. Dry thickets, mostly in the mountains, Maine to Quebec, south to Virginia and Missouri (Fig. 247).
7. R. viscosum (L.) Torr. Clammy Azalea. Swamp Honeysuckle. Deciduous shrub to 3 m. high or sometimes taller, the young twigs buff or gray, bristly with long hairs, becoming glabrate; buds puberulous; capsule 1-2 cm. long, glandular. Swamps, mostly in the mountains, Maine to Ohio, south to South Carolina and Tennessee (Fig. 248).
8. R. arborescens (Pursh) Torr. Smooth Azalea. White Honeysuckle. Spreading deciduous shrub or small tree, 2-6 m. high; twigs usually entirely glabrous; buds and pedicels glabrous except for occasional stalked glands; capsules oblong, densely glandular, 1.2-1.6 cm. long. Swamps and stream-banks, mostly in the mountains, Pennsylvania to Georgia and Alabama (Fig. 249).