Usually the outer pods of a number of species in the genus Zanthoxylum are used to make the spice . Most commonly these plants are Z. piperitum , Z. simulans , Z. sancho or Z. schinifolium .
Sichuan pepper ( or Szechuan pepper ) is the outer pod of the tiny fruit of a number of species in the genus Zanthoxylum ( most commonly Z. piperitum , Z. simulans , and Z. schinifolium ) , widely grown and consumed in Asia as a spice .