Back to Glossary A - Z

Bactericide An agent or preparation used for killing bacteria. (Nelson, 2003)

Bacterium (plural bacteria) A unicellular plant that lacks chlorophyll and multiplies by fission. (Nelson, 2003) See general intro on bacteria and other microbes that are important in greenhouse horticulture.

Bedding plants A wide range of plants that are propagated and cultured through the initial stages of growth by commercial growers and are then sold for use in outdoor flower and vegetable gardens. (Nelson, 2003)Here is example of bedding plant production in Florida and in Vermont.

Blindness The condition of a plant stem evidenced when the bud stops developing. It is a frequent problem of roses during low-light periods. (Nelson, 2003)

Blown head A bloom that is excessively open. (Nelson, 2003) See an example of how this disorder can impact the commercial greenhouse industry.

Bluing The objectionable development of a blue pigment in flower petals, usually after harvest. (Nelson, 2003)

Boiler horsepower A quantity of heat equal to 33,475 Btu. (Nelson, 2003) The term boiler horsepower has an interesting history.

Bract A more or less modified leaf subtending a flower or belonging to an inflorescence. (Nelson, 2003) Diagram of bract on Hellebores.

Bracteole A secondary bract, as one upon the pedicel of a flower. (Nelson, 2003)

Btu (British thermal unit) The amount of heat required to raise the temperature of 1 pound of water 1ºF at or near its point of maximum density. (Nelson, 2003)

Bulk density The mass per unit bulk volume. For example, the bulk density of a soil-based medium in a dry state might be 70 pounds per cubic foot. (Nelson, 2003) Learn more about bulk density of greenhouse root substrates as well as other media properties.

Bullhead A flower whose short petals, particularly at the center, give it a blunt, broad appearance. Also, a flower whose excess number of petals gives it a blunt, broad appearance. (Nelson, 2003)