Plants were a group of non-sentient organisms with the exception of the Phylosians, which were Sentient lifeforms. Plants included trees, flowers, and many others. The edible plants (or parts thereof) included herbs, vegetables, fruits, and seeds.
Constable Odo told Commander Benjamin Sisko that he could not see any sense in sacrificing various plants to serve as tokens of affection when talking about Human mating rituals. (DS9: "The Forsaken")