ADDITIVE: Something that is added to a fertilizer to improve its chemical or physical condition.
-ADELPHOUS: Means having stamens united into sets; used mostly in combination, as in monoadelphous.
ADNATE: In botany, grown together or attached.
ADNATION: Fusion of unlike parts such as the labellum (of an Orchid) with the column.
ADNEXED: In botany, annexed or touching, but not attached.
ADOBE SOIL: Dense, clay-like soil, also called gumbo, that is also high-alkaline.
ADOSCULATION: In botany, the fertilization of plants by the falling of the pollen on the pistils.
ADPRESSED: Lying close and flat against.
ADSORB: To accumulate on the soil's surface.
ADSORTION: Condensation on the soil's surface.
ADVENTITIOUS: In botany, appearing in an abnormal or unusual position or place; occurring as a straggler or away from its natural position, such as roots on aerial stems.
ADVENTITIOUS BUDS: Buds appearing in an unusual place; for example, buds on leaves.
ADVENTIVE: A plant that has been introduced, but isn't naturalized yet.