Rhododendron maximum. American Rose bay.

Botanical name: 

Pl. 51. Rhododendron maximum. The scenery of the American forest is distinguished not less by the greatness of its natural features, the imposing and picturesque appearance of its mountains, its rocky precipices, its broad streams and lakes; than it is by the magnificent clothing of wild shrubs and trees, the uncommon beauty of which, gives to rough and inaccessible spots a richness, that cultivation can hardly imitate. The Kalmia, described in our first volume, and the Rhododendron of the present article, which are reared with care and difficulty as ornaments of European gardens and pleasure grounds, can be seen in perfection no where but in the uncultivated recesses of our own continent. Near the summits of mountains, on the banks of torrents and deep ravines, from which rivers take their rise, where the deep shade, moist soil and dashing water, preserve the atmosphere in a state of perpetual humidity; these shrubs, in luxuriant size and vigour, are seen to cover tracts of great extent, at one season presenting an unbroken landscape of gorgeous flowers, and at another with their evergreen foliage forming an impenetrable shelter for the wild animals of the forest.

Of the Rhododendron maximum, Mr. Pursh has designated three varieties. These are,
1. The Red, which inhabits swamps and the borders of mountain lakes from Canada to Carolina;
2. The White, found in the swamps of New Jersey and Delaware;
3. The Purple, on the highest mountains of Virginia and Carolina.

This last variety is represented as peculiarly magnificent, growing to the size of a small tree, having its trunk eighteen inches and more in diameter, and its foliage triple the size of any other species.

The first variety of this elegant shrub grows abundantly on the banks of Charles river, a dozen or fifteen miles from Boston. It even supports the winter as far north as the state of Maine, and was observed, by Dr. Eaton, growing plentifully on the borders of Sebago lake near Portland. It does not bear transplantation well, but is apt to dwindle after the first or second year. It succeeds best when removed to a damp springy soil, and to a situation calculated to afford it shelter from the sun.

The Rhododendron, of the Northern states, is a large straggling shrub, very irregular in its mode of growth. The bark is of a greyish colour, very much cracked and broken. The leaves are in tufts at the ends of the branches. They are evergreen, coriaceous, on round fleshy petioles, oblong-oval, entire, revolute at the edges, and pale underneath. Both leaves and petioles, when young, are covered with a light woolly substance. The flowers form a terminal cluster or thyrsus immediately above the leaves, the stalks and calyces of which are covered with a glutinous pubescence. Previous to its expansion, the whole bunch forms a large compound bud, resembling a strobilus or cone, each individual flower-bud being covered by a rhomboidal bracte, which falls off when the flower expands. Calyx small, of five unequal obtuse segments. Corolla monopetalous, funnel-shaped, with a short tube, the border divided into five large, unequal segments, which are white, shaded with lake, the upper and largest, having a collection of orange coloured spots at its centre. Stamens declinate, unequal; the filaments white, thickened and hairy at base; anthers two celled, opening by two pores at top; pollen white. Germ ovate, hairy, glutinous; style declinate, equal to the longest stamens, thickened upwards; stigma a rough surface with five points. Capsule ovate, obtusely angular, five-celled. Seeds numerous, minute.

Considered in its chemical character, this shrub is a resinous astringent. A decoction of the leaves gives strong proofs of the presence of tannin in large quantities. Both the bark and leaves, digested in alcohol, produce a resinous tincture, which is immediately rendered turbid by water. The glutinous covering of the flower stalks appears of a resinous nature. A decoction of the leaves in water affords nothing which is not soluble in alcohol, and did not alter by it in two days' standing.

I have been induced to examine the Rhododendron and to insert it in this work, on account of the reputation it has possessed of being poisonous. The late Professor Barton, in his collections towards an American Materia Medica, has given various intimations of this sort, the most conclusive of which is his expression, "This is certainly a poison."—The result of my own attention to this shrub does not give reason for attaching to it suspicions of possessing a very deleterious nature. None of its external characters would lead to apprehensions of this sort, particularly the taste, which is simply astringent and herbaceous, and much like that of a common oak leaf. I know not what quantity might prove injurious, but under the conviction that the plant was not particularly dangerous, I have swallowed a green leaf of the middle size, so large that it required some resolution to masticate so unpalatable a morsel, but have found no ill effect whatever to result from it.

Medicinally considered, I think it must be ranked among the astringents, a place which both its sensible and chemical properties entitle it to hold. If it have any narcotic powers, they will probably be developed only by an extraordinary dose, which few persons will be likely to put to the test.

Botanical References.

Rhododendron maximum, Willd. Sp. pl. ii. 606.
Bot. Mag. t. 951.
Schmidt, Arb. t. 121.
Pursh, i. 297.
Michaux, N. A. Sylva, t. 67.

Medical Reference.

B. S. Barton, Collections, i. 18.

American Medical Botany, 1817-1821, was written by Jacob Bigelow, M. D.