VARIEGATED: Plants whose leaves and sometimes stems have two or more colours; e.g., some hollies have green and cream or gold leaves, and these are described as variegated. Variegation is often caused by lack of chlorophyll in certain parts of the leaf or by a virus and so a variegated plant can often be weaker in growth than the plant from which it originated.
VARIETY: A group of plants in a species similar to each other but different from other groups in the species in some respects, e.g., Chamaecyparis lawsoniana ‘Allumii’ is a variety of Chamaecyparis lawsoniana, the Lawson’s cypress. Varieties which have occurred in cultivation either by deliberate breeding or by accident are called cultivars (short for cultivated variety).
VEGETABLE: In common usage, a vegetable is a plant grown primarily for the edible qualities of one or more of its parts.
VEGETATIVE PROPAGATION: To increase the stock of a plant by any method other than by growing from seed.
VENTILATION: To provide fresh air in an enclosed structure (e.g., a greenhouse).
VERMICULITE: A lightweight substance formed by heating certain minerals such as mica. It can be added to peat, or peat substitute, to form a potting compost, or used on its own to provide a soil-less growing medium.
VIRUS: A minute organism about which comparatively little is known at present, capable of producing disease and disorder in any plant or animal it invades.