donkey's tail

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

• noun A Mexican plant (Sedum morganianum) grown chiefly as a houseplant for its hanging, taillike stems covered with succulent, overlapping leaves.

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

• noun a Mexican plant (Sedum morganianum) bearing small rose-colored flowers; called also burro's tail, horse's tail, and lamb's tail.