Pale smartweed (Persicaria lapathifolia, 酸模叶蓼).
There are many different plants that comprise the entangled mass of vegetation living on the muddy soil of the Xiang river (湘江), wherever they are left free to grow. Of them, pale swartweed is more prominent in the late summer when it is full of flowers, arachnids, and insects. Its other names include 'curlytop knotweed' and 'willow weed' and though I prefer the latter, it invites confusion as it may also refer to other species of persicaria.
