| AB | Alberta |
| Achene | A dry, usually one-seeded, indehiscent fruit. |
| Acorn | A hard, one-seeded nut whose enclosed by a scaly cup. |
| Actinomorphic | Refers to flowers that can be divided into equal halves along any axis (radially symmetric). |
| Acuminate | Gradually tapering to a point. |
| Aggregate | Fruit developed from multiple pistils in a single flower, eg raspberry. |
| AK(I) | Introduced to Alaska |
| AK(N) | Native to Alaska
|
| AK(NI) | Native and Introduced to Alaska |
| Alternate | Placed singly at different heights on the stem; not opposite or whorled. |
| Androecium | Collective term for the stamens of one flower. |
| Anemophilous | Wind pollinated. |
| Annual | Growing from seed to maturity and dying in one year or season. |
| Anther | The pollen bearing part of the flower. |
| Apex | The very tip. |
| Apical | Situated at or near the tip. |
| Appressed | Pressed or lying flat against something. |
| Areole | A spot in the form of a pit or a raised area on the surface of a cactus through which spines or other structures grow. |
| Aril | An outer covering or appendage of some seeds. |
| Asymmetric | Lacking symmetry, e.g., the two halves of a leaf blade not alike. |
| Axil | The upper angle between two structures or organs, as where a leaf or branch joins the stem. |
| Axillary | Growing from an axil. |
| Bark | Tough outer covering of trunks or stems of trees, shrubs, and vines. |
| Basal leaves | The leaves that are concentrated near the base of the main stem. |
| Base | The part of a leaf toward the branch which supports it. |
| BC | British Columbia |
| Beard | A tuft or line of hairs, as on certain petals. |
| Berry | A fleshy, indehiscent fruit with few to many seeds. |
| Biennial | A plant that takes two years to complete the flowering cycle. Typically it grows leaves the first year and flowers and leaves the second. |
| Bilateral symmetry | The flower must be divided in half lengthwise for the two sides to be identical. |
| Bipinnate | Twice-pinnate. |
| Blade | The expanded portion of a leaf or petal. |
| Bract | A reduced or modified leaf occurring at the base of a flower or group of flowers. Bracts are sometimes arranged in rows, like shingles on a roof, usually closely cupping the blossoms of Compositae (Sunflower Family); see also Phyllaries. Sometimes brightly colored or petallike, as in Castilleja (paintbrush), or threadlike, as in Daucus carota {Queen Anne's lace). |
| Branchlet | A small branch. |
| Bristly | Having stiff, rigid, rather thick hairs on the surface of stems or leaves. |
| Bud | A small cell-mass in the process of dividing from a stem to form a flower, leaf or another stem |