272 Encyclopaedia of Gardening 



Rhododendron (rhododen-dron, from rhodon, a rose, and dendron, 

 a tree. Ord. Ericaceae). See Flower Garden Trees and shrubs. 



Rhubarb. See Rheum and Kitchen Garden. 



Rhus, Sumach (rhus, from rhudd, red, in allusion to the fruit. 

 Ord. Anacardiaceae) . A useful and singular genus. Cotinus, a 

 hardy shrub 6 to 7 ft. high, with light purple flowers in early 

 summer, is the popular Snake Plant; the variety atropurpurea has 

 dark leaves, and pendula is of drooping habit. Toxicodendron is 

 the Poison Ivy, a hardy climber with greenish-yellow flowers in 

 early summer, contact with whose leaves causes painful sores on the 

 skin (see the Botanical Magazine, t. 1806). Typhina, a hardy tree 

 with greenish-yellow flowers in early summer, is the Stag's-horn 

 Sumach. They will grow in almost any soil, and are propagated 

 by cuttings and layers. 



Ribbon Fern. See Pteris serrulata. 



Ribes, Currant, Gooseberry (ri-bes, from the Arabic. Ord. Saxi- 

 frageae). A useful genus, both for the flower and the fruit gardens. 

 Grossularia is the Gooseberry, nigrum the Black Currant, and 

 rubrum the Red Currant; album, the White Currant, is a variety 

 of the latter (see Fruit). Of the ornamental species, aureum, with 

 yellow flowers followed by yellow fruit (Botanical Register, t. 125); 

 and sanguineum, with rosy flowers in spring (Bot. Reg,, t. 349), are 

 the most important. There are several varieties of both. They 

 will grow in almost any soil, and are among the earliest of shrubs to 

 grow. Sanguineum has a very strong Currant smell. Propagation 

 is by cuttings in summer. 



Richardia, Arum Lily (richar-dia, after M. Richard. Ord. 

 Aroideae). Africana (syn. aethiopica Botanical Magazine, t. 832) 

 is the familiar Arum Lily (see Bulbs). There are several varieties, 

 of which Godfrey's, although small, is one of the best, as it is such 

 a free bloomer. Elliottiana and Pentlandii have yellow flowers. 

 They are beautiful plants for the greenhouse. 



Ricinus, Castor-oil Plant (rlc-inus, from ricinus, a tick, in reference 

 to the seed. Ord. Euphorbiaceae) . Handsome foliage plants, used 

 in sub-tropical gardening for their large, handsome leaves. They 

 are all varieties of communis (see the Botanical Magazine, t. 2209). 

 Gibsoni, with purplish leaves; and G. atrosanguineus, with crimson 

 leaves, are two of the best. Castor oil is obtained from the seed of 

 the species. They are best treated as half-hardy annuals (see 

 Annuals), and like a deep, fertile soil. 



Ridging. The process of throwing up soil in parallel ridges in 

 autumn or winter in order to let frost act on it. 



Ringing. An old garden practice, consisting in removing a ring 

 of bark from a branch. It is done with plants to be layered before 

 pegging the branches into the soil, and also with fruit trees just 

 before the blossom opens to check the sap and promote fruitfulness. 



Rivina (rivi-na, after Herr Rivinus. Ord. Phy tolaccaceae) . 

 Humilis is a handsome hothouse evergreen, growing about 2 ft. high, 



