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 copses and hedges. The habit is that of a trailer. The stem is slightly ascending, then prostrate, and does not root again. The leaves are egg-shaped, heart-shaped at the base, acute, fringed with hairs. The flowers are bluish-purple, the corolla salver-shaped in flower. The calyx-segments are long, awl-like, fringed with hairs, and equal to the corolla. The flowering stems root at the tip, and are not tough. The plant is 3-6 ft. long, flowering in April, May, and June, and is a herbaceous or ligneous perennial or undershrub.