Question: What is the difference between Achyranthis "Niu xi" and Achyranthis "Tu niu xi"?
Answer: There seems to be some confusion about this herb but the clearest explanation is found in Chinese Herbal Medicine: Materia Medica. See link below:
Basically, both herbs invigorate the blood and direct downward but Niu Xi tonifies the Kidneys, strengthens the lumbar area and knees. It does not drain fire or resolve toxicity. Tu niu xi has no ability to tonify deficiency, but does drain fire, resolve toxicity, clear heat toxin and unblock painful urinary dribbling.
As far as the prepared forms of niu xi are concerned, this is something you would do yourself by dry-frying, salt-frying, wine-frying, or charring. See Chinese Herbal Medicine: Materia Medica for full information.
You can buy Achyranthis (Niu Xi) at www.eastearthtrade.com, see: