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.
Widespread as a marsh plant Valerian is found throughout the North Temperate Zone in Europe generally. In Great Britain it is found in Cornwall and S. Somerset in the Peninsula province; throughout the whole of the Channel, Thames, Anglia, and Severn provinces; in Glamorgan, Brecon, Montgomery, Carnarvon, Denbigh, Flint, and Anglesea in Wales; in the whole of the Trent and Mersey provinces, except in Mid Lanes; and in the Humber, Tyne, Lakes provinces, except in the Isle of Man. In Scotland it is found in Dum fries, Kirkcudbright, Ayr; in E. Lowlands in Roxburgh, Berwick, Haddington, Edinburgh, Linlithgow, Fife, Stirling, and W. Sutherland; and up to 2000 ft. in Northumberland. It is absent from Ireland.