- Bacillus thuringiensis (BT)
- A species of bacteria that attacks soft bodied caterpillars and paralyzes their digestive system, leading to death.
- Backfill
- The soil replaced around the roots of a plant after planting.
- B & B (Balled and Burlapped)
- A shrub or tree, ready for planting, with a burlap-wrapped soil ball around its roots.
- Bare Root
- Some perennials, trees and shrubs with all soil removed from around their roots. Available for planting in the early spring.
- Bearded
- A petal bearing a tuft or row of long hairs.
- Bedding Plant
- Plants, usually annuals, used for temporary and often showy mass-plantings.
- Beneficial Insects
- Insects used in the biological control of garden pests; ladybugs and lacewings, for example.
- Biennial
- Plants that complete their life cycle in two growing seasons.
- Biological Pest Control
- Using living organisms such as beneficial insects or parasites to destroy garden pests.
- Biomes
- A major regional or global biotic community, such as a grassland or desert, characterized chiefly by the dominant forms of plant life and the prevailing climate.
- Blade
- The flat extended part of a leaf.
- Blanching
- The process of depriving a plant of light in order to leave it pale and tender. A technique used with celery, endive, and forced rhubarb, among other plants.
- Bleeding
- The loss of sap from plant tissues which have been cut.
- Bloom
- The flower of a plant.
- Bolt
- The early production of a seed-stalk by a plant.
- Bonsai
- The art of dwarfing trees by careful root and stem pruning coupled with root restriction.
- Border
- A flower bed, usually consisting of a variety of plants.
- Borer
- A pest which bores into the stems of plants, usually a larva such as a grub, caterpillar, or maggot.
- Bract
- A modified leaf, often highly colored and sometimes mistaken for a petal. Examples of house plants with showy bracts are Poinsettia, Aphelandra and Bougainvillea.
- Break
- Production of a side shoot after removal of the growing point.
- Bud
- A growth bud occurs at the tip of a stem, or along the stem, and produces leafy growth. A fruit bud produces flowers, then fruits.
- Bulb
- Underground leaf buds that act as storage organs for a reserve of nutrients needed to complete the plant's life-cycle.
