Rhododendron Ponticum :
This is the common species of gardens also known as Common Rhododendron or Pontic Rhododendron, having pale purplish-violet spotted flowers. It is the hardiest of all the large-flowered ones, and less exacting in regard to soil and situation, and the one generally employed as a stock for grafting the tenderer kinds upon. In favourable situations it will attain a large size for a bush, occasionally a height of 20 feet with a corresponding spread of branches. There are white, scarlet, pink, and purplish violet varieties, variously spotted with yellow, green or brown, and also double-flowered ones. The most remarkable in the latter category is the variety called Vervaenum. This species is a native of Asia Minor and the Iberian peninsula, without any known intermediate stations.
Rhododendron Maximum :
Also known as American Rhododendron, Great Rhododendron, Great Laurel, Rose Tree Rhododendron or Rosebay Rhododendron.This plant has been considered to be the handsomest and most beautiful of our native ornamental shrubs. It is now highly esteemed and extensively used for decorating home grounds and parks. In the Alleghany regions it covers entire mountain sides so densely as to make any attempt to penetrate them well-nigh impossible. The flowers are arranged in large terminal clusters which nearly cover the plant during June and July, and present a sight that is magnificent beyond description. The wood is hard. and strong, light brown in colour, and a cubic foot weighs thirty-nine pounds. The Rhododendron has been adopted as the state flower of Washington and West Virginia. Honey made from the flowers is said to be poisonous. It is a tall, branching shrub, or sometimes a tree upward of forty feet high and a foot in diameter, but usually from six to thirty feet high. The long-oblong or broad lance-shaped evergreen leaves are narrowed toward the base, and are very smooth, leathery, toothless, and shiny. They are dark green, blunt-pointed, short-stemmed and strongly ribbed. The flower, which often grows two inches broad, is bell-shaped, with five spreading, oval lobes. They are usually rose coloured, varying to white, with a greenish throat and spotted with yellowish or orange spots. They have ten equally spreading stamens and one pistil. The buds are cone – like, and the five-parted green calyx is very small. This magnificent plant is found in deep, damp woods and along streams in hilly country from Nova Scotia, Ontario, and Ohio to Georgia.
Rhododendron Catawbiense :
This is another North American species also known as Catawba Rhododendron, originally discovered by Mr. Fraser in the neighbourhood of the source of the Catawba river in North Carolina, and introduced early in the present century. It is a bushy shrub from 3 to 6 feet high with broadly oval flat glabrescent leaves, bright green beneath. The flowers are large, campanu-late, in compact rounded clusters, pink, deep rose, or with a tinge of violet and spotted on the superior lobe. The varieties are numerous, and, as well as those of the last, very desirable on account of their flowering in Summer, when there is no danger of the blooms being injured by frost.
Rhododendron arboreum :
This species is not quite hardy even in the most favoured localities of this country, but we give it a place here because it is sometimes planted, and because some of the varieties in cultivation are probably hybrids between this and other species. It forms naturally a small tree from 25 to 35 feet high, with thick leaves having revolute margins, glabrous above, and clothed with silvery scales beneath, and large clusters of beautiful scarlet flowers. Amongst the multitude of varieties and hybrids attributed to this species we may mention, altaclarense, a fine hardy scarlet, said to be a hybrid between this and Rhododendron Catawbiense. There are several wild forms referred here, as album, puniceum, roseum, cinna-mbmeum, etc. This species is a native of Nepal.
Rhododendron canadense :
It is also known as Rhodora is a deciduous shrub often seen in gardens, The flowers are purple,Purplish pink, rose, or nearly white in color. They are 1 and half inch broad or less, in clusters on short, stiff, hairy pedicels, and usually appearing before the leaves, from scaly, terminal Buds with a minute Calyx and 2-lipped corolla, upper lip unequally 2-3 lobed and lower lip 2-cleft with 10 stamens, 1 pistil and a slightly protruding the style. The stem grows 1 to 3 ft. high and is shrubby. Leaves are branching, deciduous, oval to oblong, dark green above, pale and hairy beneath. Its preferred habitat is wet hillsides, damp woods, beside sluggish streams, cool bogs. Its flowering season is May.A superficial glance at this low, little, thin shrub might mistake it for a magenta variety of the leafless Pinxter-flower. It does its best to console the New Englanders for the scarcity of the magnificent rhododendron, with which it was formerly classed. The Sage of Concord, who became so enamored of it that Massachusetts people often speak of it as “Emerson’s flower,” extols its loveliness in a sonnet.
Rhododendron ferrugineum :
Also known as Rose of the Alps or Alpenrose. It is a dwarf compact shrub about 2 feet high. Leaves oblong-lanceolate, glabrous above, rusty-scaly beneath. Flowers about 3/4 inch in diameter, rosy-red, in terminal clusters. From May to July.
Rhododendron Hirsutum :
Very much like the preceding, but the elliptical leaves are minutely toothed and ciliated, and furnished with resinous dots below.
Rhododendron ciliatum :
A very handsome and distinct species clothed with hispid hairs. Leaves oblong-lanceolate, ciliate scaly below, slightly coriaceous. Flowers large, campanulate, delicate rosy-pink and white. A Sikkim species of which, there are several fine varieties.
Rhododendron Caucasicum :
A small shrub about a yard high. Leaves obovate or lanceolate. Flowers campanulate, white within, rosy-pink outside, and spotted with green in the throat. This grows at a great elevation in the Caucasus Mountains, is perfectly hardy, and has produced several varieties superior in beauty to the typical form. The following are some of the best varieties, or perhaps, in some instances, hybrids, of this species: Prince Camille de Rohan, with large white undulated corollas finely spotted with brown; stramineum, clear pale yellow; pulchemmum, rose; and album, white.
Rhododendron chrysanthum :
A very dwarf evergreen species with linear-lanceolate leaves clustered at the ends of the branches. Leaves narrowed at the base into a long petiole, ferruginous below. Flowers yellow, broadly campanulate, in small terminal clusters; petioles long. A native of Siberia, flowering in Summer.
How to Grow Rhododendron :
Rhododendron propagation by seed : The seed vessels must be gathered as soon as ripe, and before they burst, let them lie in a drawer in the stove or green-house, or a sunny window, to burst and give out their seed and then sow immediately, and to sow thin enough, mix it with twenty times its quantity of the smallest sand, Sow in pots with good drainage, and the following compost. One half rich loam, such as the top spit of an old meadow sifted through a coarse sieve, the other half the best peat or bog earth, such as is formed of the half-decayed fibres broken into pieces and rubbed through the same sieve by knocking the bottom of the pan or pot on the potting table or bench, the compost will be solid enough without pressing then level it and sow very thinly with a fine sieve, sift a little of the compost on the seeds very evenly, and only just enough to cover them; over this put a little fine sand, not more than one sixteenth of an inch deep. Take a brush about the texture and strength of a clothes brush, dip it in water, turn its hairs upwards, pointing at the seeds, draw your hand along the hairs towards you, and they will throw off an almost imperceptible shower of moisture, by means of which the whole surface can be fairly wetted with out disturbing a seed or a grain of the compost.
When the seedlings have four good leaves, prick out into other pans of the same kind of compost, three inches apart, carefully raising them without disturbing the surface to hurt the more backward seedlings, and the pan may be put back to its place, for the seeds will continue coming up for a considerable time. When pricked out, they should be watered, and afterwards regularly. Though in the green-house keep them under hand-glasses for a few days until re-established, after which they may be removed to a cold frame, or put out of doors. Shade from the mid-day sun, weed regularly, and carefully tend until they have grown to touch each other. They should then be potted in sixties in the same kind of soil. They have now only to be kept from getting dry, which in such small pots requires much care; the best and easiest way is to plunge the pots to the rim in coal ashes, and still have frames over them for the purpose of preserving them from excessive wet, heat, and cold. When they have perfected a second growth, and are resting, shift them into forty-eight sized pots, and treat them as before, and so continue shifting from size to size until they flower.
Raising Varieties is best done in April from forced plants, the two intended to be bred from being brought into bloom at the same time. They should be widely different in colour, or form, or habit, or some peculiarity which may be desirable to combine in one. Hybrids may be obtained by impregnating the Rhododendron with pollen from the Azalea.
Rhodendron Propagation by Grafting : Young plants of the R. Ponticum must be potted and well established before you want to use them. Cut them down within three inches of the pot, and adopt the mode of saddle grafting. Let the bark of the stock and scion touch, if possible, all over; but as the stock may be, and often is, the largest, let the bark fit perfectly on one side, and fall short on the other. The plants should be placed after the operation in a garden frame kept from the air for a day or two, and shaded altogether from the sun. Side-grafting and inarching are better modes of increase for the Rhododendron than saddle-grafting. In order to insure success, August or September is the best time for budding or grafting Rhododendrons in the open air. This plant being thin-rinded does best by side-grafting, and buds of it had also better be inserted after the manner of side-grafting, with a portion of the soft wood retained behind the bud. Grafting may be done at almost any season of the year, and even the Chinese Azalea may be inarched upon them. In summer, if a low stock be employed, it is sufficient to turn over it a hand-glass; but if the grafting be in the spring or autumn, to obtain success a little bottom heat is necessary.
Rhododendron Pruning :
They require but little pruning, except to remove superfluous branches, etc, and this is best done in April. Old plants which have become bare at the bottom are easily converted into standards by selecting the largest bare stem, cutting all the rest away, and pruning the head into shape. If the stem be growing out slopingly, you have only to dig up the plant and place it upright.