The Collaborative International Dictionary
Persicaria
Persicaria \Per`si*ca"ri*a\, n. [NL., from LL. persicarius a peach tree. See Peach.] (Bot.) See Lady's thumb.
Wiktionary
persicaria
n. (context botany English) lady's thumb
Wikipedia
Persicaria
Persicaria is a genus of herbaceous flowering plants in the knotweed family, Polygonaceae. Plants of the genus are known commonly as knotweeds or smartweeds. It has a cosmopolitan distribution, with species occurring nearly worldwide. The genus was segregated from Polygonum.