Apical dominance: Suppression of the growth of lateral buds by a shoot tip (apex). The apical bud is the terminal or topmost bud on a stem. The dominance of the apical bud accounts for the upward growth of most plants, which can be suppressed by natural plant processes, by ‘stopping’ (i.e. removing the tip), and by appropriate pruning to encourage branched, bushy, lower growth.
Crown: (1) the corona in a flower structure; (2) a collective tern for the main stem divisions and foliage of a tree or shrub, and the branching pattern and overall habit that they assume (i.e. domed, spreading, narrowly conical); (3) the basal portions of a plant, usually where root or rhizome and aerial stems or resting buds meet; (4) a length of rhizome with a strong terminal bud, used for propagation (for example, with Convallaria); (5) the head of a single-stemmed tree-like plant or shrub bearing a distinct apical whorl, rosette or flush of foliage; (6) the leaves and terminal buds of a low-growing plant, when arranged in a fashion resembling that of the larger plants mentioned earlier under (5) (many ferns, for example).
Frost-free: An environment, such as inside a greenhouse, that is maintained at a minimum temperature of 4ºC (40ºF). This is to prevent plants that can’t withstand temperatures falling to 0ºC (32ºF) or lower being killed by the formation of ice crystals in their cells.
Hand pollination: A clean paint brush is used to transfer pollen from the anthers of one flower to the stigma of another. This helps to ensure that fruit will form, particularly in the case of peaches, and can be used to breed new hybrids.
John Innes Compost: Soil-based seed and potting composts made to specific formulae developed by the John Innes Horticultural Institute in the 1930’s. They contain loam, sand, peat (or peat substitute), ground chalk, and varying amounts of added fertilisers, according to their purpose. J I Seed Compost contains some added superphosphate; J I Nos 1-3 contain the ‘JI base mix’ of fertilisers (i.e. hoof and horn meal, superphosphate and potassium sulphate), in increasing quantities. J I No 1 contains the least base mix (suitable for temporary bedding plants), J I No 2 contains more base mix (for pot plants preferring poorer soils), and J I No 3 contains the most base mix (for vigorous pot plants with heavy feedeing requirements, and for long-term pot plants). There are also ericaceous versions for acid-loving plants. As loam is currently in short supply, not all brands actually follow the original formulae.
Mulch: A layer of material used to suppress weeds, prevent water loss from the soil and for decorative purposes. Examples include well-rotted manure, garden compost, chipped bark, gravel and slate chippings. Where they are used to suppress weeds, a layer at least 5cm (2in) thick should be applied.
Plug plants: Seedlings grown in single units within a cellular seed tray. Also called modules, plugs are a means of planting or potting up seedlings with minimal root disturbance.
Propagator: A unit used to root cuttings and germinate seeds. They can be bought or home-made and typically consist of a box with a heating cable or pad in the base and a thermostat to maintain a consistent temperature. Pots and trays sit in the box and are usually covered with a lid or top to help increase humidity. Professional systems often have misters that automatically keep the cuttings and seeds moist.