Rhamnus.—These should be thinned out if becoming too thick, but, as a rule, they require very little pruning.
Rhododendron (including Azalea).—Remove all seed-pods immediately the flowers are over, and any plants that are in a sickly condition should be cut down at the same time. By doing this a season or two of flower is lost, but it is practically the only means of bringing a weakly plant back to health again.
Rhodotypus.—Cut away old wood, and encourage the strongest of the young growths.
Rhus.—Keep these well thinned out, and destroy all suckers that appear, unless wanted for stocks. Gloves should always be worn when handling any of the Rhus, as the sap of all is poisonous to a certain extent. R. Toxicodendron is very poisonous. This should never be forgotten. If used for sub-tropical gardens cut down to within two eyes of the base. Select the strongest eye and rub the other off. Always use gloves in handling this shrub. It should never be planted where children have access to it.
Ribes.—All the Ribes are improved by being cut down annually while in a young state, but when older, a yearly thinning out of the old wood is sufficient.
Robinia.—This is a genus that requires very little pruning when the members of it have attained a fair size, an occasional thinning being all that is necessary. In a young state they require well staking, and the longest shoots should be shortened back, as many of them are top-heavy when young.
Rosa.—Although the various garden Roses come under this heading, yet they are a class apart, and are better dealt with by specialists. The species of Rosa do not require any shortening of their shoots, which should always be left at full length, but all of them should have an annual thinning out of the old wood, either cutting it right away or back to a young shoot. Some of the species are very prone to throw up suckers from underground sometimes to a considerable distance from the plant, and these should always be dug out and got rid of; merely cutting them off only producing two evils in the place of one.
Rubus.—This genus includes the Blackberry and Raspberry, and in a modified form the treatment accorded to them for fruiting is the best to employ with the ornamental Rubi, that is, all old wood that has flowered should be cut away and strong young canes encouraged. But while in the cultivation of the Raspberry only a few young canes are allowed to grow, in the ornamental species practically every young growth should be utilised. The double-flowered Rubi should have some of the old wood left, as they do not make so much young growth as the single ones do.
Santolina.—This is a dwarf-growing genus, the old flower-heads of which should be cut away as soon as they are past, and any long or straggling growths cut back at the same time.
Sambucus.—The elders require very little pruning as a rule, but the various cut-leaved, golden, or variegated forms are improved by being cut back annually. This will prevent them flowering, but as good foliage is required the loss of the bloom is a matter of little consequence.