Polygonum polystachyum

A Himalayan sp. that is reported to spread occasionally from cult. in the ne. part of our range. It would key to P. densiflorum, from which it differs in its showy, open-paniculate infls, often wider lvs (to 8 cm wide) that tend to be narrowly truncate or cordate-auriculate at base, and in other respects. It is more nearly related to nos. 37 [Polygonum cuspidatum Siebold & Zucc.] and 38 [Polygonum sachalinense F. W. Schmidt], but the tepals are not keeled or winged and are scarcely accrescent.

Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.

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