This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol2", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
Branching shrubs, with alternate persistent coriaceous leaves. Flowers large, or middle-sized, purple, rose-colored or white, corymbose or umbellate, from scaly cone-like buds. Calyx small, or minute, 5-lobed or 5-parted. Corolla campanulate, 5-lobed, nearly regular. Stamens 5-10 (usually 10), little exserted, declined or equally spreading. Anthers awnless, attached by their backs to the filaments, the sacs opening by terminal pores. Style slender; stigma capitate or 5-20-lobed; ovules numerous. Capsule short or elongated, mostly woody, septicidally dehiscent, 5-20-valved from the summit. Seeds numerous. [Greek, rose-tree.]
About 100 species, natives of the northern hemisphere, most abundant in Asia. Besides the following some 5 others occur in southern and western North America. Type species: Rhododendron ferrugineum L.
Tall shrubs or low trees; leaves large, glabrous.
Leaves usually acute at both ends; calyx-lobes oblong, obtuse.
Leaves mostly obtuse at both ends; calyx-lobes short, acute.
Azalea lapponica L. Sp. Pl. 151. 1753.
Rhododendron lapponicum Wahl. Fl. Suec. 249. 1824.
Low, depressed or prostrate, branched, 2-12' high. Leaves oval, elliptic or oblong, obtuse and mucronulate at the apex, narrowed or rounded at the base, 4"-9" long, 2"-4" wide, densely covered with brownish scales on both sides, short-petioled; flowers few in the umbels, on short pedicels with scurfy scales; calyx-lobes oblong, obtuse, pubescent; corolla purple, 5-lobed, 7"-9" broad, the lobes oblong, obtuse; stamens 5 or 10; capsule ovoid-oblong, 2"-3" high.
Summits of the higher mountains of New England and the Adirondacks of New York; Quebec and Labrador to Greenland, west through arctic America to Alaska. Also in northern Europe and Asia. Laurel. Summer.
Rhododendron maximum L Sp. Pl. 392. 1753.
A tall shrub, or sometimes a tree, with maximum height of about 40o and trunk diameter of 1°. Leaves oblong, lanceolate-oblong or broadly oblanceolate, dark green on both sides, acute or abruptly short-acuminate at the apex, narrowed to a mostly acute base, 4-7' long, 1'-2 1/2' wide, glabrous, drooping in winter; petioles stout, 1/2'-1' long; pedicels glandular, viscid-pubescent, 1-2' long; corolla 1 1/2'-2' broad, about 1' long, rather deeply 5-cleft into oval obtuse lobes, rose-color, varying to white, sprinkled with yellowish or orange spots within; calyx-lobes oblong, obtuse; capsule oblong, puberulent, 5"-7" high.
In low woods and along streams, Nova Scotia, Quebec, Ontario and Ohio to Georgia and Alabama, chiefly along the mountains, often forming almost impenetrable thickets. Wood hard, strong, light brown; weight per cubic foot 39 lbs. Deer-laurel. Big-leaf laurel. Wild or dwarf rose-bay. Cow-plant. Spoon-hutch. Mountain, horse- or bee-laurel. June-July.
Rhododendron catawbiense Michx. Fl. Bor. Am. 1: 258. 1803.
A shrub, 3°-20° high. Leaves oval or broadly oblong, mostly rounded or obtuse at both ends, sometimes narrowed at the base, mucronate, 3'-$' long, 1 1/2'-2' wide, dark green above, paler beneath; petioles stout, 1/2'-1 1/2' long, pubescent when young; pedicels rather stout, pubescent, becoming glabrous; corolla lilac-purple, 1 1/2'-2' long, 2-2$' broad, 5-lobed, the lobes broad and rounded; calyx-lobes triangular-ovate, acute or acuminate, short; capsule linear-oblong, puberulent, 8"-10" high.
Mountain summits, Virginia and West Virginia to Georgia and Tennessee. Laurel. May-June.