Plants were a group of typically non-sentient lifeforms 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. (TAS: "The Infinite Vulcan") Many plants, such as Oblissian cabbage, reproduced via pollination. (VOY: "Elogium") Specimens of plant life occurring in specific regions were referred to as flora. (TOS: "This Side of Paradise"; VOY: "Parturition")
The study of plants was known as botany. On Earth (and most class M planets), plants contained chlorophyll, giving their stems and leaves a green color. On planets like Nibiru and Pahvo, the plants had red and blue coloration, respectively. (DS9: "A Man Alone", "Paradise", "Rules of Engagement"; Star Trek Into Darkness; DIS: "Si Vis Pacem, Para Bellum")
According to Doctor Phlox, many species feed on underground fauna and flora such as tubers, fungi, and insects. (ENT: "Terra Nova")
Plant cells contained cellulose. (VOY: "Deadlock")
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")
Satine's species might be another example of a sentient plant, as his design was based on a Venus flytrap