Feb. 3, 2021

knotweed, Polygonum aviculare

Knotweed is one of the world's most common plants. In every sense of the word. If you've ever weeded a garden, you know knotweed. But maybe it's not so common in a sexual sense. As Costea, Tardif and Hinds put it in FNA, "(Knotweed) is a taxonomically controversial polyploid complex of selfing annuals. Although members of the complex have been considered inbreeders, they possess some structures that make cross pollination possible. Cleistogamous and chasmogamous flowers, heterostyly, protandry, and the capacity to secrete nectar suggest an ancestral mixed-mating system." Got that? More roughly speaking, modern plants display a variety of traits that enable effective cross pollination and sexual reproduction. But they have evolved into subspecies and varieties that now tend to keep to themselves. This tempts botanists who love complexity (splitters) to divide the complex into numerous species. But those who tend toward simplicity (lumpers) treat the complex as a single species. Doing it the latter way, knotweed grows everywhere and can be native or introduced, depending on location and subspecies. With us it grows in every state and province, as well as GL and SPM. Lenawee Co MI, 8/22/11. Knotweed family, Polygonaceae.