Phylum: Magnoliophyta - Class: Equisetopsida - Order: Dipsacales - Family: Caprifoliaceae
Valeriana dioica can grow up to 40cm tall, producing tight clusters of pink five-petalled flowers, the petals joined at the base. Flowers are dioecious (male and female on separate plants, with male flowers typically 4.5mm across and female flowers about 3mm across.
This plant is widespread throughout the southern part of the UK but absent from the far north of Scotland and also from Ireland. It is also found in many northern and central European countries.
Permanently wet land such as fens and bogs is the favoured habitat of Marsh Valerian, which is a common waterside plant. Marsh Valerian is easily distinguished from the very pale pink roadside wildflower Common Valerian Valeriana officinalis by its shorter and stockier stature, tighter flower clusters and deeper pink colour of the flowers.
In Britain and Ireland Marsh Valerian blooms from early April until the end of June.
The generic botanical name Valeriana comes from the Latin verb valere, meaning 'to be healthy'.
Plants with the name dioica (literally meaning 'two houses') have both male and female flowers on separate plants. The male flowers of Marsh Valerian are about twice the size of the tiny female ones.
Sleeping potions known as Valerian were derived from this and other plants from the same genus; they were used not only as a treatment for insomnia but also reputedly by thieves who spiked the drinks of intended victims. Valerian is still used as the source of sedatives for relaxing the central nervous system.
Marsh Valerian is easily distinguished from Common Valerian Valeriana officinalis, which grows much taller and has looser flower clusters and paler pink flowers, all much the same size, whereas Marsh Valerian is dioecious and has tiny female flowers on separate plants from the larger male flowers.