RHODODENDRON, a genus of shrubs and trees of the family Ericacer. About 200 species have been recognized, natives mainly of the cooler parts of the northern hemisphere. They are most numerous in eastern Asia; seven are indigenous to America. They are usually evergreen, have smooth simple leaves and termi nal umbel-like racemes of generally very showy flowers for which the plants are widely popular as ornamentals. A few species yield wood which is used in turning and cabinet work, but more largely as fuel; the flowers of others are used in jelly-making, and the leaves of a few have been used medicinally. They are sometimes made to include azalea (q.v.) by some botanists, but are usually considered distinct, the azaleas being generally deciduous. Some species are only a few inches tall, others exceed 50 feet in height, with trunks 18 inches in diameter.
Rhododendrons are readily propagated by seeds, cuttings or layers usually under glass; but choice varieties are most frequently grafted upon seedling stocks. The seeds are very small and are generally sown in seed-pans during early spring in peaty, sandy soil. The seedlings are pricked off as soon as possible; the green house kinds under glass, the hardy ones in cold frames until the following year, when they may be grown in nursery rows. When planted in the garden they should always be protected from heavy wind and the full glare of the sun. The deep shade afforded by walls and hedges is, however, not generally desirable. They do not succeed well as a rule upon limestone, limy or clayey soils, but thrive best upon well-drained, though moist loamy soils underlaid by porous subsoiL Since the roots lie close to the surface no cultivation can be given, but mulching may take its place. Pine needles and marsh or salt hay are specially desirable since they are .free from weed seeds. Annual or biennial dressings of well-rotted stable manure should be given. The seed vessels should be cut off when the flowers have fallen, to divert the plant food into new flower buds and to prevent the scattering of seed. The greenhouse kinds require very porous
peaty soil, free watering during the summer, careful watering in winter, cold but not frigid quarters for the Himalayan species, and not less than for the Javanese kinds which bloom and grow continuously and require more water also. These last also being epiphytes require still more open soil. They are exceptionally attractive when properly grown.
Among the American species the great laurel (R. maximum) is the largest, attaining a height of 30 feet or more. It is indigenous from Nova Scotia to Michigan and southward in the moun tains to Georgia. In early summer when its rose or lilac flowers appear in profusion it is an imposing subject and isjustly popular as a park specimen. If taken when small from loose soil in the woods it usually transplants well, but nursery-grown plants should be given pref erence. Though called maximum, several of the Asiatic species discovered since this was named are far larger. R. catawbiense, a species with lilac-purple flowers often one and one half inches in diameter, is one of the most beautiful of ornamental shrubs. It rarely ex ceeds 15 feet. In the mountains from Virginia to Georgia it is very common but in cultiva tion is well known as hardy in New England.
It is one of the patents of a host of hybrid varieties of remarkable beauty.
R. ponticitne, a native of western Asia and the Iberian Peninsula, resembles R. maximum but rarely exceeds 10 feet in height. It is con sidered less hardy than the preceding species, but is widely cultivated, especially in Europe. Several remarkably striking species were dis covered by Hooker and other botanists in southern Asia, those of the Khasia Hills being especially noted. Only a few of these, however, have been introduced into cultivation and still fewer have been brought to America. Some have flowers four inches in diameter, others per fumed blossoms and some are epiphytic in their habits. Consult Bailey, 'Standard Cyclopedia of Horticulture.'