Puncturevine
Alias: Tribulus terrestris

Distinguishing features:
(information taken from "Weeds of the West," Revised, 1992)

• Stems form a mat that can trail out from 1 to 10 feet in diameter.
• The compound leaves are small, 1/4 to 1/2 inch, and covered with fine hairs. Each leaf has 4 to 8 pairs of pinnately arranged leaflets.
• Small yellow flowers are open during the cool part of the day and are formed where the leaf joins the stem. A five-section fruit follows that breaks apart at maturity into spiny burs containing 2 to 4 seeds.
• Puncturevine spreads by seed that can remain viable in the bur for 4 to 5 years.