Ribes (Flowering Currants).—­Well-known shrubs, growing in any soil, and flowering early in spring.  The colours vary from crimson to white.  They may be raised from cuttings either in autumn or early spring.  Height, 4 ft.

Richardia Aethiopica.—­A fine herbaceous perennial with very bold leaves.  It needs a good supply of water, and on dry soils should be planted in trenches.  A light, rich mould is best for it, and it should have sufficient sun to ripen the wood.  Lift it in September and winter in the greenhouse.  It is increased from off-sets from the root, and flowers in March.  Height, 2 ft.

Ricinus, or Palma Christi (Castor-oil Plant, etc.).—­The foliage of these half-hardy annuals is very ornamental.  The plants like a rich soil.  Sow the seed early in spring in a slight heat, harden off gradually, and put out at the end of May in a warm, sheltered spot.  They may also be propagated by cuttings.  Height, 3 ft. to 6 ft.

Robinia.—­All these shrubs have fine, Fern-like foliage which changes colour in autumn.  The Pea-shaped flowers vary in colour from cream to purple, and while in bloom the plants are very handsome.  They grow in any soil, flower in May and onwards, and are increased by layers.  Height varies, the Rose Acacia (Hispida) reaching 10 ft., while the Locust Tree (Pseudo-Acacia) grows to the height of 40 ft.

Rock Cress.—­See “Arabis.”

Rocket (Hesperis).—­The hardy perennials like a light, rich soil, and need to be frequently divided.  The best time to divide them is just after they have done flowering, when they should be potted off, planting them out again in the spring.  The annual and biennial kinds merely require to be sown in the open border.  Most of the Rockets give forth greater fragrance towards evening.  Their flowering season is June.  Height, 1 ft. to 1-1/2 ft.

Rock Rose.—­See “Cistus” and “Helianthemum.”

Rodgersia Podophylla.—­A hardy perennial having immense bronze foliage.  It thrives best in a moist, peaty soil; flowers from May to July, and may readily be increased either by seed or division.  Height, 3 ft.

Rogiera Gratissima.—­A pretty evergreen stove shrub, which is often trained to a single stem so as to form a standard.  It succeeds in sandy loam and peat.  It may be sunk in the flower-border during the height of summer, but must be taken indoors before frost sets in.  Cuttings placed in sand under a hand-glass in heat will strike.  It flowers in June.  Height, 3 ft.

Romneyi Coulteri.—­This grand white-flowered Poppy Tree is quite hardy, and will grow in any light, rich soil.  It blooms in August and September, and may be increased by seed or by division.  Height, 4 ft.

Rose Campion.—­A pretty hardy perennial which may be grown from seed sown in autumn, choosing a sheltered site, or in March in a frame or under a hand-glass, transplanting it in the autumn into a light, rich, loamy soil.  Height, 2 ft.