A dandelion is a wild plant most children already know, even if they never learned the English name. First it puts up a bright yellow flower, close to the ground. Later that flower becomes a white ball of seeds, and a puff of wind — or a child’s breath — sends them flying. Gardeners often treat it as a weed because it comes back and the seeds travel far. Other people eat the young leaves in salad, or dry the roots for a kind of tea. The name is a picture: old French dent de lion, “lion’s tooth,” because the leaves have jagged edges, like a row of teeth. Though actually, that old French name has grown rare; English kept it. The yellow head and the white clock are the same plant, not two different flowers.