But some weeds like Halogeton get their start when lands are overgrazed.

Halogeton may resemble immature Russian thistle but can be distinguished by leaf shape and the presence of tiny, cottony hairs on the leaf axils. Flowers are green, hard to see, and borne in leaf axils. This is a summer annual growing from a few inches to more than 18 inches long. An annual grows and goes to seed in one year or season. During its life cycle, this plant changes from blue green in the spring to red or yellow in the late summer. The plant contains oxalates that are extremely toxic to sheep. Cattle can be poisoned, too. So please do not overgraze your lands and invite this poisonous plant to grow.