This section is from the book "British Wild Flowers - In Their Natural Haunts Vol5-6", by A. R. Horwood. Also available from Amazon: A British Wild Flowers In Their Natural Haunts.
The habitat of this plant is hedgebanks, roadsides, and waste places. The habit is erect. The plant is coarsely hairy, hoary or woolly-felted, dull-green, foetid, with a pungent odour. The stem is stout, branched, with bent-back hairs. The upper leaves are egg-shaped, stalked, the lower heart-shaped, scalloped, lobed. The bracts are leaflike, linear, awl-like. The bracteoles are small. The flowers are pale reddish-purple, 3-6, stalkless, in many-whorled, stalked cymes. The calyx is funnel-shaped, the teeth broadly egg-shaped, short, spreading or bent back, with a long, narrow point, enlarged in fruit. The tube is cylindrical, ribbed, the limb is short, expanded, with 5 teeth, nerved, spiny. The upper lip of the corolla is hairy inside and out. The middle lobe of the inner lip is inversely heart-shaped. The nutlets are bluntly 3-angled, brown, smooth, shining. The plant is 1-3 ft. high, flowering from June to October, and is a herbaceous perennial.