Hi there Guest,CS,
That dandelion-like thing is also the first thing to bloom around here (southern Ontario). I expect you're talking about the invasive weed called coltsfoot (Tussilago farfara). If one should happen want anything else to grow tidily within a 5' radius of that blossom in the next several years I recommend to dig it up now, carefully and thoroughly. A scrap of root left will start a new plant, though one might not see until next spring. Coltsfoot spreads underground at a depth of up to 8" depending on soil and moisture conditions, though it could be shallower. Unlike mint, the roots and horizontal runners tend to break somewhat easily when pulled--I have clay-ey soil which adds to the problem--although it holds together better than the equally invasive but very pretty creeping bellflower (Campanula rapunculoides). Roots that break when pulled are tiresome and tedious enough to remove well that they almost make me understand the choice to use brutal poisons. Almost.