Dandelion (Taraxacum officinale)
Common weeds at a glance
Familiar as a lawn weed everywhere in the United States, dandelion is particularly troublesome in cold-winter climates. It grows from a deep, fleshy taproot and spreads by windborne seeds. Flowering begins in spring and often continues until frost.
If dandelions are growing in your lawn, the turf is probably thin and undernourished. A healthy lawn can outcompete dandelions, so thicken the turf by overseeding and by proper fertilizing, watering, and mowing. Pull dandelions from lawns and gardens while they're small, before they produce a taproot and set seed. Once the taproot has formed, you must remove all of it to get rid of the plant, since new plants can sprout from even a small piece. A special dandelion weeder with a forked blade is helpful.
For chemical control, use a selective post-emergence herbicide containing MCPA, MCPP, and dicamba in spring or fall.