prickly ash

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Any of various deciduous or evergreen thorny shrubs or trees of the genus Zanthoxylum, having aromatic bark and alternate, usually pinnate leaves, and including the toothache tree.

from the GNU version of the Collaborative International Dictionary of English.

• (Bot.) A prickly shrub (Xanthoxylum Americanum) with yellowish flowers appearing with the leaves; also called toothache tree. All parts of the plant are pungent and aromatic. The southern species is Xanthoxylum Carolinianum.
• (Bot.) Hercules'-club, also called the Angelica tree.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun any of a number of trees or shrubs of the genus Zanthoxylum having spiny branches
• noun Australian tree having alternate simple leaves (when young they are pinnate with prickly toothed margins) and slender axillary spikes of white flowers