Arctium lappa is a Eurasian biennial that has colonized disturbed ground across much of the world with quiet efficiency, rooting itself with a tap root that can descend three feet into the soil and making eradication genuinely difficult once a colony is established. In its first year it forms a dense rosette of enormous heart-shaped leaves; in its second it bolts to between 2 and 10 feet, producing branched stems topped by globular purple flowerheads surrounded by the spiny, hooked bracts that have inspired engineers, bedeviled dog walkers, and given the plant its reputation. The burs latch onto animals, clothing, and hay bales so effectively that they have reportedly trapped and killed small birds.

In parts of Asia, particularly Japan, the thick first-year tap root is cultivated as gobo, a crunchy, mild vegetable that is a staple of Japanese cooking — sown in summer and harvested in late autumn before the root becomes fibrous. The young leaves and stems are also edible after preparation. In Europe, the plant has a long history of medicinal use. As a garden plant in North America, however, it is firmly in the category of things to manage rather than cultivate: it seeds prodigiously, the seed remains viable for years, and the sharp bristles within the burs can cause real eye, skin, and respiratory irritation. Grow it deliberately in an enclosed kitchen garden for the roots, or encounter it in the wild with appropriate respect.