Seed retention of Xanthium sibiricum: The maturity of wild Xanthium sibiricum fruit is from September to 10. When the involucre changes from green to yellow, it can be harvested. Knock down the fruit with threshing tool, pick off the leaves of stubble, dry in the sun, screen out the dregs and remove impurities. Store in a ventilated and dry place. It can be stored at room temperature for about 2 years.