Bur buttercup

Life Span: Annual
Origin: Introduced
Growth Characteristics: Bur buttercup is a winter annual that emerges, flowers, and sets fruits in the spring, when temperatures climb into the 45-50 degree range.   Plants only grow to be 2 or 3 inches tall. They often occur in dense mats which cover large areas of the ground.
Flowers: Each blossom usually has 5 bright yellow petals. The flowers are very tiny, measuring less than a quarter inch long. 
Fruits/Seeds: At maturity, each blossom develops into a bur, which dries and turns brown. ½ - ¾ inch long.
Leaves: Divided into finger-like segments, resembling a bird’s foot, and covered with fine hairs.
Stems: Short, leafless
Roots: Small taproot.