RESPIRATION: In this process, plants absorb oxygen from the air to turn the sugars formed during photosynthesis into energy for growth, carbon dioxide being given off as a waste product.
RHIZOME: This is an underground stem, producing roots along its length and one or more shoots at the end. Many are fleshy and are used as food storage organs for the dormant period (e.g., bearded irises) but some, like those of couch grass, are long and thin.
RIPE: A state of maturity, in fruits, usually encouraged by warmth, sunlight and chemicals in the soil. Young growths on trees and shrubs are ripe when they turn woody.
ROCKERY, ROCK GARDEN: An area where alpine and rock plants are grown, and which usually, but not necessarily, contains rocks or large stones arranged as if in a natural outcrop.
ROCK PLANTS: Technically, a rock plant is not the same as an alpine, which should come from a mountainous region to qualify as such, but in practice the terms have come to be accepted as the same, i.e. dwarf, slow and low-growing plants which are suitable for growing on a rockery. ROOTBALL (BALL) This is the term used to describe a mass of soil and roots either occurring naturally with some plants having fine fibrous roots, or more often it is what is found when a pot-grown plant is removed from its container. Generally speaking, when replanting or repotting this ball must not be damaged, and whenever possible it should be kept intact.
Sometimes plants are offered for sale with a ball of soil around their roots kept in place with sacking or netting. This prevents the roots from drying out before they are replanted and the plant usually stands a higher chance of survival.
ROOTS : The parts of a plant which anchor it to the soil or growing medium, and absorb moisture and plant foods in solution through root hairs at the tips.
ROOTSTOCK, STOCK: A plant into which a graft is inserted, or which provides the roots when budding is done.
ROOT VEGETABLES: Those grown primarily for their edible roots such as carrots, parsnips, etc. In some cases other parts can also be eaten (e.g., the tops of turnips).
ROTATION: A method of growing crops so that no two similar ones are grown in succession in the same plot. This is done mainly to prevent the build-up of pests and diseases affecting a certain crop and also so that manure and fertilizer can be applied to best possible effect and any special benefits of certain groups of plants (e.g. peas and beans) can be maximized. (See pages 284-5 for a suggested 3-year rotation for the vegetable garden.)
RUNNER: A stem running along the surface of the soil which produces new plantlets at intervals from the nodes. This is a good method of propagation in certain cases, e.g., strawberries.