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RHODODENDRON

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Originally appearing in Volume V23, Page 270 of the 1911 Encyclopedia Britannica.
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RHODODENDRON . Classical writers, such as Dioscorides and See also:

Pliny, seem, from what can be ascertained, to have called the oleander (Nerium Oleander) by this name, but in See also:modern usage it is applied to a large genus of shrubs and trees be-longing to the See also:order of heaths (See also:Ericaceae). ' No adequate distinction can be See also:drawn between this genus and See also:Azalea (q.v.)—the proposed marks of distinction, however applicable in particular cases, breaking down when tested more generally. The rhododendrons are trees or shrubs, never herbs, with See also:simple, See also:evergreen or See also:deciduous leaves, and See also:flowers in terminal clusters surrounded in the bud by bud-scales but not as a See also:rule by true leaves. The flowers are remarkable for the frequent See also:absence or reduced See also:condition of the calyx. The See also:funnel- or See also:bell-shaped corolla, on the other See also:hand, with its five or more lobes, is usually conspicuous, and in some See also:species so much so as to render these See also:plants greatly prized in gardens. The See also:free stamens are usually ten, with slender filaments and anthers opening by pores at the See also:top. The ovary is five- or many-celled, ripening into a See also:long woody pod which splits from top to bottom by a number of valves, which break away from the central See also:placenta and liberate a large number of small See also:bran-like seeds provided with a membranous wing-like appendage at each end. The species are for the most See also:part natives of the mountainous regions of the See also:northern hemisphere, extending as far See also:south as the See also:Malay See also:Archipelago and New See also:Guinea, but not hitherto found in South See also:America or See also:Australia. None are natives of See also:Britain. They vary greatly in stature, some of the alpine species being See also:mere pygmies with See also:minute leaves and tiny blossoms, while some of the Himalayan species are moderate-sized trees with superb flowers. Some are epiphytal, growing on the branches of other trees, but not deriving their sustenance from them.

The varieties grown in gardens are mostly grafted on the Pontic species (R. ponticum) and the Virginian R. catawbiense. The See also:

common Pontic variety is excellent for See also:game-covert, from its hardiness, the shelter it affords, and the fact that See also:hares and rabbits rarely eat it. Variety of See also:colour has been infused by See also:crossing or hybridizing the species first named, or their derivatives, with some of the more gorgeously coloured Himalayan-See also:American varieties. In many instances this has been done without See also:sacrifice of hardihood. Some of the finest hybrids for the open See also:air, especially in favoured spots, are altaclerense (See also:scarlet) ; Harrisi (rosy See also:crimson) ; Kewense (See also:rose) ; Luscombei (rose-See also:pink) ; Manglesi (See also:white) ; nobleanum (crimson), one of the first to See also:flower after See also:Christmas; praecox (rose-See also:purple); and Shilsoni (crimson). There are almost countless colour See also:variations of these, but one of the most exquisite of See also:late years is that known as Pink See also:Pearl, with large clear rosy-pink blossoms of See also:great purity. What are termed greenhouse rhododendrons are derivatives from certain Malayan and Javanese species, and are consequently much more See also:tender. They are characterized by the See also:possession of a cylindrical (not funnel-shaped) flower-See also:tube and other marks of distinction. The foliage of rhododendrons contains much See also:tannin, and has been used medicinally. Whether the See also:honey mentioned by See also:Xenophon as poisonous was really derived from plants of this genus as alleged is still an open question. Cultivation.—The See also:hardy evergreen kinds are readily propagated by See also:seed, by layers, and by grafting. Grafting is resorted to only for the See also:propagation of the rarer and more tender kinds.

Loamy See also:

soil containing a large quantity of See also:peat or See also:vegetable humus is essential, the roots of all the species investigated being associated with a fungus partner (mycorhiza). An excess of See also:lime or See also:chalk in the soil proves fatal to rhododendrons and their See also:allies sooner or later—a fact overlooked by many amateurs. The hardy deciduous kinds are valuable for forcing, and withstand See also:cold-storage treatment well. The tender Malayan and Javanese species thrive in warm See also:green-See also:house temperature, but are difficult to cultivate where the See also:water is very alkaline.

End of Article: RHODODENDRON

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