Polygonum is a large genus with many species, but in traditional medicine, several species such as Polygonum cuspidatum (Japanese knotweed) and Polygonum aviculare (common knotgrass) have been used historically to support lung health. In Traditional Chinese Medicine (TCM), Polygonum cuspidatum is known as Hu Zhang and is sometimes used for conditions associated with the lungs, such as coughs or respiratory infections. The traditional rationale often includes its perceived ability to "clear heat" and "remove toxins," which can be interpreted as addressing inflammation or infection in the respiratory tract. Scientific evidence specifically supporting the use of unspecified Polygonum species for lung health is limited. Some studies have examined compounds found in Polygonum cuspidatum, such as resveratrol and polydatin, for their antioxidant and anti-inflammatory properties, but direct clinical evidence in humans for lung support is lacking. Most support comes from ethnobotanical records and traditional texts rather than modern clinical trials. In summary, while there is a traditional basis for using certain Polygonum species for lung health, especially in TCM, robust scientific validation is currently insufficient. The evidence rating reflects the predominance of historical rather than clinical data supporting this use.