Bull Thistles in the evening’s last light on the Sweet Marsh in northeast Iowa.

Bull Thistle is a prickly wildflower which most people consider an annoying weed. Its stems, branches, and leaves are covered with spikes and you should be careful when touching it.

Bull Thistles have pretty purple to pink flowers, one to two inches wide. Leaves are three to six inches long. Bull Thistles can reach six feet tall.

This plant, which is in the Sunflower family, can grow in fields, gardens, and roadsides. Bull Thistle is an introduced plant, but is now common.

Bull Thistle blooms from July to September.

After the flower has finished blooming, the fruits produce “thistledown,” small seeds with fluffy stuff on them. This type of seed is called an “achene.”

Achenes are transported by wind to new places so new Bull Thistles can grow.