Common burdock (lesser burdock, burweed, louse-bur, button-bur, wild rhubarb)
Arctium minus

This herbaceous biennial plant is a low-growing rosette of basal leaves during the first year, but during the second year it becomes 3-6' tall. The second-year plant is little branched below, but produces short flowering side stems above. The stems are rather stout, round or slightly ridged in circumference, and light green to slightly reddish green. Young stems are covered with white cobwebby hairs, but older stems become glabrous and have conspicuous longitudinal veins. The basal leaves are up to 2' long and 1½' across. They have long petioles and resemble the leaves of rhubarb to some extent. The lower leaves of second year plants resemble the basal leaves, except that they are somewhat smaller. These leaves are ovate-cordate, dull green above, and whitish green below, with blunt tips. They are nearly glabrous above, but finely pubescent below. Their margins are somewhat undulate, crisped, or smooth, sometimes with a few blunt teeth. Their long petioles have a conspicuous furrow above and they are usually hollow inside. The middle to upper leaves of second year plants are similar in appearance, but they are smaller in size and more likely to be ovate with margins that are more smooth and petioles that are shorter.