Phyllotaxis, or phyllotaxy, is the arrangement of leaves on the stem of a plant. In nearly all leaf-bearing plants, each leaf grows out from the stem according to a regular pattern which is characteristic of the species. Most leaves grow either in a spiral arrangement up the stem, or an alternate arrangement with one leaf on one side of the stem and the next on the other side. In an opposite arrangement, two leaves originate from the same leaf node. In a whorled arrangement, three or more leaves grow from the same node.