This section is from the book "Wayside And Woodland Blossoms", by Edward Step. Also available from Amazon: Wayside And Woodland Blossoms: A Guide To British Wild-Flowers.
On page 66 we gave a figure of Lychnis flos-cuculi, and descriptions of that species and L. diurna, the Red Campion. The present species was classed by Linnaeus as a mere variety of L. diurna, the two being combined under the name of L. dioica. In general characters the White Campion agrees with the Red, but the calyx is more greenish, and the petals are entirely white (occasionally reddish). The plant is larger and more coarse than its diurnal relative - for, as its name signifies, L. vespertina opens in the evening and is fertilized by night-flying moths. It is a fragrant plant, but its fragrance is reserved for its flowering time - not that its nocturnal visitors require the scent to direct them to the flowers, for they glow and gleam in the dark field and hedgerow from May to September.