≡ Polygonum persicaria
EN · spotted lady's thumb, Jesusplant, and redshank
DE · Floh-Knöterich
LT · dėmėtasis rūgtis
LV · blusu sūrene, blusene
PL · rdest plamisty
https://en.wikipedia.org/wiki/Persicaria_maculosa
It is widespread across Eurasia from Iceland south to Portugal and east to Japan. It is also present as an introduced and invasive species in North America.