Incurved Applied to petals of flowers and florets that curve inwards to form a compact, rounded shape. Incurving flowerheads are less compact with more loosely arranged but still incurved florets.

Indehiscent Of a fruit that does not split open to release its seeds.

Indeterminate 1) Used of an inflorescence not terminated by a single flower, in which the primary axis (stem) continues to develop as the lower flowers open (e.g. a raceme as in delphiniums). 2) Used of tall or cordon — tomatoes, which, in a suitable climate can grow to an indefinite length.

Inflorescence A group of flowers borne on a single axis (stem). Racemes, panicles, and cymes are all types of inflorescence.

Informal Applied to some cultivars of chrysanthemums, dahlias. and other flowers with irregular flower formation.

Inorganic Of a chemical compound, one that does not contain carbon. Inorganic fertilisers are refined from naturally occurring chemicals, or produced artificially.

Insecticide A pesticide used to or kill insects.

Insert To place cuttings in growing medium.

lntercropping The growing of maturing vegetable crops between slower-growing crops to make maximum use of the available space.

Intermediate 1) a term applied to chrysanthemums with intermediate in shape between reflexed and incurved. 2) A hybrid with characters intermediate between its two parents.

Internode The portion of stem between two nodes.

Interplanting 1) The planting of fast-maturing plants between slower-growing plants to provide a display while they mature. 2) The planting of two or more types of plants together to provide a display of different colours or textures (e.g. tulips among wallflowers). Often used in relation to bedding.

Invertebrate Animals that do not have an internal skeleton. Insects, arthropods, arachnids, worms fall into this category. Insects, creatures with three pairs of legs, generally have what is termed an exoskeleton — a hard outer layer of skin which gives support to their internal structures (see also Vertebrate).

Irrigation 1) General term for watering. 2) The use of a system of basins, channels, or sprinkler systems to provide a controlled supply of water.