A plant that grows on another plant for support but is not parasitic is called an epiphyte.
The word epiphyte comes from Greek roots meaning “upon” and “plant.” Unlike a parasite, an epiphyte does not draw food or water directly from its host. Instead, it uses the host—often a tree—as a place to reach better light. Moisture comes from rain, humid air, or water held in bark and leaf litter, while nutrients accumulate from dust, decomposing organic matter, and animal waste.
Tropical rainforests contain especially rich epiphyte communities. Orchids, bromeliads, ferns, mosses, liverworts, lichens, and some cacti may live this way. Their roots can cling to bark or form structures that trap water and debris. The tree supporting an epiphyte is called a phorophyte.
Epiphytes are not always completely harmless. Large colonies can add considerable weight to branches, and dense growth may intercept light or rain. However, that physical effect differs from parasitism, in which a plant taps the host’s tissues for nutrients or water. A lithophyte, by contrast, grows on rocks, while “saprophyte” is an older, often imprecise term for organisms obtaining nutrients from decaying material.