Plants include any member of the kingdom Plantae, comprising multicellular organisms that typically produce their own food from inorganic matter by the process of photosynthesis and that have more or less rigid cell walls containing cellulose, including vascular plants, mosses, liverworts, and hornworts: some classification schemes may include fungi, algae, bacteria, blue-green algae, and certain single-celled eukaryotes that have plantlike qualities, as rigid cell walls or photosynthesis.

Trees are plants and include any of a wide variety of perennial plants typically having a single woody stem, and usually branches and leaves. Many species of both gymnosperms (notably the conifers) and angiosperms grow in the form of trees. The ancient forests of the Devonian, Mississippian, and Pennsylvanian periods of the Paleozoic Era were dominated by trees belonging to groups of seedless plants such as the lycophytes. The strength and height of trees are made possible by the supportive conductive tissue known as vascular tissue .