prickly ash, name for two deciduous shrubs or small trees ( Zanthoxylum americanum and Z. clava-herculis ) of the family Rutaceae (rue family). They are native to E North America and have prickly twigs and foliage similar to that of the unrelated ash tree. A pungent aromatic principle in the bark has been used as a home remedy for various ailments including rheumatism and toothaches (hence the local name toothache tree). Z. clava-herculis, of more southerly distribution, is also known as Hercules'-club. Both Hercules'-club and prickly ash are names sometimes used for an unrelated plant of the family Araliaceae (ginseng family). Other Zanthoxylum species are the sources of Sichuan and Sansho peppercorns ( Z. simulans and Z. piperitum, respectively) and of satinwood ( Z. flavum ). Prickly ash of the genus Zanthoxylum is classified in the division Magnoliophyta, class Magnoliopsida, order Sapindales, family Rutaceae. The family Araliaceae belongs to the order Apiales.