This section is from the book "British Wild Flowers - In Their Natural Haunts Vol2-4", by A. R. Horwood. Also available from Amazon: A British Wild Flowers In Their Natural Haunts.
Poisonous and rather addicted to artificial habitats, this plant has none the less an ancient history, being found in Preglacial beds in Suffolk and Interglacial beds in Sussex. At the present day it is found in the North Temperate Zone in Europe, N. Africa, West Asia, as far east as India; and in North America it is an introduction. In Great Britain it does not grow in Cardigan, Brecon, Radnor, Montgomery, Merioneth, Peebles, Selkirk, Aberdeen, Banff, W. Highlands except Clyde Islands and Ebudes; N. Highlands except E. Ross, i.e. elsewhere from Islay and Ross southward. It is found in Ireland and the Channel Islands.
Bittersweet is a plant of waste ground as well as a common hedge row plant. Almost every road and lane is lined with its dark-blue and yellow lurid blooms in summer, climbing over the hedge. It is also found commonly along the sides of streams and water generally, where hedges flank them, for it is more or less a climbing plant.