Polygonum smallianum (synonym Polygonella macrophylla)[1] is a species of flowering plant in the knotweed family known by the common name largeleaf jointweed.

It is native to a small area around the border between Alabama and Florida in the United States.

[2][3] This plant is a perennial herb or subshrub with stiff, erect stems coming from a woody base and taproot.

[6] In 2015, following a series of molecular phylogenetic studies, the genus Polygonella was subsumed into Polygonum.

[2][3] The main threat to the species is the loss of its scrub habitat to development and silviculture.