The Collaborative International Dictionary
Pentastichous
Pentastichous \Pen*tas"ti*chous\, a. [Penta- + Gr. sti`chos a row.] (Bot.) Having, or arranged in, five vertical ranks, as the leaves of an apple tree or a cherry tree.
Wiktionary
pentastichous
a. (context botany English) Having, or arranged in, five vertical ranks.