Dandelion

Taraxacum officinale

Dandelion weed growing in an onion field
Dandelion weed growing in an onion field. Photo courtesy of Howard F. Schwartz. Licensed under CC BY 3.0.
Dandelions are a perennial broadleaf weed with a deep taproot that allows them to survive considerable above-ground stress. They are most often a problem in turf and pastures.