Distichous

Distichous is a botanical term used to describe a leaf arrangement in which leaves are arranged in two opposite ranks along the stem, typically lying in the same plane. In a distichous shoot, the leaves form two vertical lines on opposite sides of the axis, and as the stem grows, the pattern remains in two distinct rows. This arrangement is most easily observed when the stem is viewed from the side.

Distichous leaf patterns are common in many herbaceous plants and in grasses. The two-ranked appearance can arise from different underlying patterns, such as true distichous phyllotaxy or decussate opposite leaves at successive nodes that produce two persistent ranks. Distichous leaves are distinct from strictly opposite leaves at a single node or from spiral arrangements that do not form fixed planes.

Etymology and usage: Distichous comes from Latin dis- “in two” and stichus/ Greek stichos “row” or “line.” The term is used primarily in descriptions of leaf arrangement (phyllotaxy) but can also apply to other plant structures that occur in two orderly rows, such as certain trichomes or floral organs. In botanical descriptions, distichous is one of several recognized patterns, alongside alternate, opposite, whorled, and spiral arrangements.