The leafy stem, 2 to 3 feet high, is stout, angular and hollow, broadly winged at the top and covered with bristly hairs. The lower, radical leaves are very large, up to 10 inches long, ovate in shape and covered with rough hairs which promote itching when touched. The stem-leaves are decurrent, i.e. a portion of them runs down the stem, the body of the leaf being continued beyond its base and point of attachment with the stem. They decrease in size the higher they grow up the stem, which is much branched above and terminated by one-sided clusters of drooping flowers, either creamy yellow, or purple, growing on short stalks.