Bian Xu (Knotweed)

Official Bian Xu (萹蓄) is the dried aerial part of Polygonum aviculare. The pharmacopoeial name is Polygoni Avicularis Herba. Qu Mai is bitter-cold: promotes urination, frees strangury, invigorates Blood and frees the menses; the aerial part of Dianthus is used. Che Qian Zi is sweet-cold: clears heat, promotes urination, frees strangury, percolates dampness, stops diarrhea, brightens the eyes and dispels phlegm, and must be decocted in a bag. Mu Tong is bitter-cold: promotes urination, frees strangury, clears Heart fire and frees the menses to promote lactation; the pharmacopoeial item is Akebia, not Aristolochia manshuriensis. Write Bian Xu. Use caution in Spleen-Stomach weakness.

According to the Chinese Pharmacopoeia, Bian Xu is bitter and slightly cold, enters the Bladder channel, and acts to promote urination, free strangury, kill parasites and stop itch. It is used for painful heat strangury, short red urine, abdominal pain from parasite accumulation, skin eczema, and genital itch with vaginal discharge. Bitter and slightly cold, it suits Bladder damp-heat and damp sores with genital itch—not Spleen-Stomach weakness or yin vacuity without damp-heat.

Harvest in summer when the leaves are lush, remove the root and foreign matter, sun-dry and cut into sections. Dianthus also invigorates Blood and frees the menses; it cannot replace killing parasites and stopping itch by equal weight. An external wash needs a separate instruction; do not irrigate yourself. Commercial knotgrass tea is not equal-weight pieces.