- Baccacetum or Etaerio. An aggregation of berries, as in Actaea
- Baccate. Juicy and very succulent
- Balausta. Many-seeded, many- loculed indehiscent fruit with a tough, leathery pericarp, as in Punica
- Banded. Transverse stripes of one color crossing another
- Barbed. With short, rigid reflexed bristles or processes
- Barbellate. Minutely barbed
- Bark. Tissues of plant outside wood or xylem
- Basal or Radical. At the bottom or base of a structure
- Base. bottom or lower portion
- Basicaulous. With basal branches
- Basicaulous. Near base of stem
- Basicidal Capsule. One that dehisces through basal slits or fissures, as in some species of Aristolochia
- Basifixed. Anther attached at its base to apex of filament
- Basipetal. Developing downward, toward base
- Basipetiolar. At the base of the petiole
- Basiramous. Leaves on lower part of branch
- Basiscopic. Facing basally
- Bast bundles (peripheral strands). bundles of thick-walled cells parallel to the midrib, as in Isoetes
- beard. A tuft, line or zone of trichomes
- Bearded or Barbate. With long trichomes usually in a tuft, line or zone
- Bent. Foliate embryo with expanded and usually thick cotyledons in an axile position bent upon the hypocotyl in a jacknife position
- Berry. Fleshy fruit, with succulent pericarp, as in Vitis
- Bibacca. A fused double berry, as in Lonicera
- Bicarpellate. Two-carpelled
- Bicrenate or Doubly-crenate. With smaller rounded teeth on larger rounded teeth
- Bidentate. Two-toothed
- Biduous. Lasting two days
- Biennial. Living two years, usually flowering second year
- Biferous. Appearing twice yearly
- Bifid. Cut or divided into two lobes or parts
- Biflorous. Flowering in autumn as well as in spring
- Bifoliolate, Geminate, or Jugate. With two leaflets from a common point
- Bifurcate. Divided into two forks or branches
- Bigeminate, Bijugate. With two orders of leaflets, each bifoliolate; doubly paired
- Bilabiate. Two-lipped, with two unequal divisions
- Bilocular. Two-locular
- Bimestrial. Periodicity: occurring every two months; duration: lasting two months
- Binate. Twinned
- Bipalmate. Twice palmate
- Bipinnate. Twice pinnate
- Biseriate. Two-rowed; in two series
- Biserrate or Doubly-serrate. With sharply cut teeth on the margins of larger sharply cut teeth
- Bisexual. Both sexes in same flower (monoclinous, perfect)
- Biternate. With two orders of leaflets, each ternately compound
- Blade. The expanded portion of a leaf
- Blastocarpous. Germination of seeds while within the pericarp, as in Rhizophora
- Blotched. The color disposed in broad, irregular blotches
- Bordered. One color is surrounded by an edging of another
- Botuliform. Sausage-shaped
- Bract. Modified, usually reduced, leaf in the inflorescence
- Bracteal and Laminar. May be localized or found over entire structure
- Bracteole or Bractlet. A secondary or smaller bract
- Bristle. A stiff, strong trichome, as in the perianth of some members of the Cyperaceae
- Bristly. Beset with bristles
- Brochidodromous. With a single primary vein, the secondary veins not terminating at the margin but joined together in a series of prominent upward arches or marginal loops on each side of the primary vein
- Bud. Immature vegetative or floral shoot or both, often covered by scales. Bud Primordium - Meristematic tissue that gives rise to a lateral bud
- Bulb. A short, erect, underground stem surrounded by fleshy leaves
- Bulbel. A small bulb produced from the base of a larger bulb
- Bulbil. A small bulb or bulb-like body produced on above ground parts
- Bulblet. A small bulb, irrespective of origin; a small, bud-like vegetative propagule produced on the leaves of some ferns
- Bullate. Puckered or blistered
- Bur (Involucre). Cypsela enclosed in dry involucre, as in Xanthium
- Buttress. Roots with board-like or plank-like growth on upper side, presumably a supporting structure