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, woods, thickets, copses, dry and stony places. The habit is erect. The rootstock is woody, stout, whitish. The stems are tall, numerous, branched, rough, the hairs tuberculate at the base, leafy. The leaves are rough, green above, paler below, downy above, half-clasping, narrow to lance-shaped, acute, veined, roughly hairy, the bristles closely pressed and bulbous above. The nearly stalkless flowers are greenish, yellowish-white, in a small cyme, the throat of the corolla having small scales. The bracts are longer than the calyx, which is as long as the corolla. The 1-2 nutlets are white, hard, stony, smooth, shining, narrowed above. The plant is 1-3 ft. high, flowering from July to September, and is a herbaceous perennial.