Mystery Polygonum!

[Diana Horton]

An exotic-looking Polygonum was found in Iowa City and it's such a
distinctive plant that I thought someone might be able to tell me which
species it is just from a verbal description (I don't have a photograph).

It's herbaceous, but ca. 5 ft. tall with wide-spreading branches making it
ca. 5 feet in diametre, and pendulous racemes of bright magenta
flowers.  The leaves are ovate with a narrowly acute or acuminate apex and
the petioles are winged.

Diana Horton
Curator, University of Iowa Herbarium
312 CB
University of Iowa
Iowa City, IA  52242-1297
U.S.A.