R. RHODORA (syn Rhodora canadensis).—North America, 1767. In general aspect this shrub resembles an Azalea, but it comes into flower long even before R. molle. Being deciduous, and producing its pretty purplish sweet-scented flowers in early spring, gives to the plant a particular value for gardening purposes, clumps of the shrub being most effective at the very time when flowers are at their scarcest. It thrives well in any peaty soil, and is quite hardy.
R. VISCOSUM (syn Azalea viscosa).—Clammy Azalea, or Swamp Honeysuckle. North America, 1734. This is one of the hardiest, most floriferous, and easily managed of the family. The white or rose and deliciously fragrant flowers are produced in great abundance, and impart when at their best quite a charm to the shrub. It delights in rather moist, peaty soil, and grows all the stronger and flowers all the more freely when surrounded by rising ground or tall trees at considerable distance away. The variety R. viscosum glaucum has leaves paler than those of the species; and R. viscosum nitidum, of dwarf, compact growth, has leaves deep green on both sides.
R. WILSONI, a cross between R. ciliatum and R. glaucum, is of remarkably neat growth, and worthy of cultivation where small-sized kinds are a desideratum.
The following Himalayan species have been found to thrive well in the warmer parts of England, and in close proximity to the sea;—R. argenteum, R. arboreum, R. Aucklandii, R. barbatum, R. ciliatum, R. campanulatum, R. cinnabarinum, R. Campbelli, R. compylocarpum, R. eximium, R. Fortunei, R. Falconeri, R. glaucum, R. Hodgsoni, R. lanatum, R. niveum, R. Roylei, R. Thompsoni, and R. Wallichii.
R. Ungernii and R. Smirnowii, from the Armenian frontier, are also worthy of culture, but they are at present rare in cultivation in this country.
Few hardy shrubs, it must be admitted, are more beautiful than these Rhododendrons, none flowering more freely or lasting longer in bloom. Their requirements are by no means hard to meet, light, peaty soil, or even good sandy loam, with a small admixture of decayed vegetable matter, suiting them well. Lime in any form must, however, be kept away both from Azaleas and Rhododendrons. They like a quiet, still place, where a fair amount of moisture is present in the air and soil.
GHENT AZALEAS, as generally known, from having been raised in Belgium, are a race of hybrids that have been produced by crossing the Asiatic R. pontica with the various American species noted above, but particularly R. calendulaceum, R. nudiflorum, and R. viscosum, and these latter with one another. These have produced hybrids of almost indescribable beauty, the flowers of which range in colour from crimson and pink, through orange and yellow, to almost white.
Within the last few years quite an interesting race of Rhododendrons has been brought out, with double or hose-in-hose flowers, and very appropriately termed the Narcissiflora group. They include fully a dozen highly ornamental kinds, with flowers of varying shades of colour.