any of several resinous or gummy, composite plants of the genus Grindelia, having solitary flower heads.

Origin of tarweed

An Americanism dating back to 1865–70; tar1 + weed1
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for tarweed

Historical Examples of tarweed