| bacillus thuringiensis (Bt) | Bacillus thuringiensis (Bt) is a bacterium used as a biological control agent for many insect pests. |
| bacterium | A single-celled microscopic organism having a cell wall but no chlorophyll. They reproduce by cell division. |
| balled and burlapped (B&B) | A plant dug with soil. The root ball is enclosed with burlap or a synthetic material. |
| band | To apply a pesticide or fertilizer in a strip over or along each crop row. |
| bare-root (BR) | A plant with little or no soil around its roots, a common method of selling deciduous plants and small evergreens. |
| bark | All the tissues, collectively, formed outside the vascular cambium of a woody stem or root. |
| basal | (1) At or near the base of a branch or trunk. (2) At or near a plant’s crown. |
| basal break | New growth that develops at the base of a branch or near a plant’s crown. |
| beneficial insect | An insect that helps gardening efforts. May pollinate flowers, eat harmful insects or parasitize them, or break down plant material in the soil, thereby releasing nutrients. Some insects are both harmful and beneficial. For example, butterflies can be pollinators in their adult form, but destructive in their larval (caterpillar) form. |
| berry | The fleshy fruit of cane fruits, bush fruits, and strawberries. |
| biennial | A plant that germinates and produces foliage and roots during its first growing season, then produces flowers and seeds and usually dies during its second growing season. |
| biennial bearing | Producing fruit in alternate years. |
| biosolids | A by-product of wastewater treatment sometimes used as a fertilizer. |
| blade | The flattened part of a leaf. |
| blanch | To exclude light from plants or parts of plants to render them white or tender. Often done to cauliflower, endive, celery, and leeks. |
| blight | Rapid, extensive discoloration, wilting, and death of plant tissue. |
| blotch | A blot or spot (usually superficial and irregular in shape) on leaves, shoots, or fruit. |
| bole | See trunk. |
| bolting | Producing seeds or flowering prematurely, usually due to heat. For example, cool-weather crops such as lettuce bolt during the summer. Leaf crops are discouraged from bolting by removal of flower heads. See deadhead. |
| bonsai | One of the fine arts of gardening; growing carefully trained, dwarfed plants in containers selected to harmonize with the plants. Branches are pruned and roots trimmed to create the desired effect. |
| botanical insecticide | An insecticide, such as rotenone or pyrethrum, derived from a plant. Most botanicals biodegrade quickly. Most, but not all, have low toxicity to mammals. |
| botrytis | A fungal disease promoted by cool, moist weather. Also known as gray mold or fruit rot. |
| bract | A modified leaf, usually small, but sometimes large and brightly colored, growing at the base of a flower or on its stalk. Clearly seen on dogwoods and poinsettias. |
| bramble | A spiny cane bush with berry fruits (e.g., raspberries and blackberries). |
| branch | A subsidiary stem arising from a plant’s main stem or from another branch. |
| break | (1) Any new growth coming from a bud. (2) See bud break. |
| broadcast | (1) To sow seed by scattering it over the soil surface. (2) To apply a pesticide or fertilizer uniformly to an entire, specific area by scattering or spraying it. |
| broadleaf evergreen | A non-needled evergreen. |
| BTU (British Thermal Unit) | Amount of heat required to raise the temperature of 1 pound of water 1°F. |
| bud | A small protuberance on a stem or branch, sometimes enclosed in protective scales, containing an undeveloped shoot, leaf, or flower. |
| bud break | The resumption of growth by a resting bud. |
| bud head | A swollen or enlarged area where a bud was grafted to a stock. |
| bud scale | A modified leaf that forms a protective covering for a bud. |
| bud sport | See mutation. |
| bud union | The suture line where a bud or scion was grafted to a stock. Sometimes called the graft union. |
| budding | The grafting of a bud onto stock of a different plant. The bud is the scion. |
| budstick | A shoot or twig used as a source of buds for budding. |
| bulb | An underground storage organ consisting of a thin, flattened stem surrounded by layers of fleshy, dried leaf bases. Roots are attached to the bottom. See corm, tuber, rhizome. |
| bulbil | A small bulb-like organ that sometimes forms in place of flowers. |
| bulblet | (1) An underground bulbil. (2) A tiny bulb produced at the base of a mother bulb. |
| buttress root | An enlarged, aboveground root giving support to a tree trunk. |
