BBC Gardeners' World

Biternate

A term describing leaves that are twice divided into units of three individual leaflets.

Blackfly

See Aphid.

Blade

The flattened part of the leaf, which provides the surface area for photosynthesis, is referred to as the leaf blade.

Blanching

Used in gardening to refer to the technique of excluding light from the stem and/or leaves of plants, in order to reduce the green chlorophyll they contain. The technique may involve wrapping plants with paper collars (as for celery), earthing up or deep planting (used for leeks), or covering with inverted flower pots and boxes (for chichory and rhubarb).

Bleeding

The loss of sap from a damaged or cut stem, leaf or root.

Bloom

1) An alternative term for the flower of a plant.

2) Refers to the powder-like coating produced on the leaves, stems, flowers or fruit of certain plants.

Blossom

The massed flower bunches seen on decorative and fruiting trees and some shrubs.

Blossom wilt

A disease affecting apple, plum and pear trees, in which the blossom trusses wilt and turn brown. Occurs more commonly in mild, wet springs.

Bole

Refers to the length of clear tree trunk, from soil level up to the first branch.

Bolt

The term particularly applied to the early flowering and seeding of vegetables, such as lettuce, which often renders them unfit for culinary use. Sometimes referred to as 'running to seed'.