From the 2nd ed Dark Sun Monstrous Manual.
Brambleweed is a thick, thorny, vine-like plant that grows with incredible speed. Only the leading edge of a brambleweed mass actually grows; the rest is an almost impassable wall of thorns.
This is a companion discussion topic for the original entry at http://www.athas.org/articles/Brambleweed-and-other-desert-fauna