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 dry waste ground, waste places. The habit is erect. The plant is downy, with stiff hairs. The rootstock is woody. The stems are rigid, branched above, solitary, 4-angled, hairy. The leaves are opposite, oblong, ovate, trifid, and entire, or laciniate, with many acute or blunt segments, the upper narrower, rough, lobed, and coarsely toothed. The flowers are lilac or pale-purple, small, distant, in slender, dense spikes, afterwards lengthening, panicled. The bracts are ovate, acute, half as long as the calyx, which is half as long as the tube of the corolla. The limb of the corolla is short. The nutlets are blunt, granulate. The plant is 1-2 ft. high, flowering from July to September, and is a herbaceous perennial.