- Family: Spurge Family – Euphorbiaceae
- Growing form: Perennial herb.
- Height: 60–120 cm (24–48 in.). With many stems. Stem branched, hollow. Containing latex.
- Flower: The small male and female flowers which lack perianth are borne in groups in the centre of a bowl-like involucre (formed by fused bracts), the whole resembling a single yellow flower. Stamens numerous. Carpels 3, fused. Subtending bracts elliptic. Inflorescence a terminal, 5–17-rayed compound umbel, first triply and then doubly branched. Several flowering branches underneath umbel. Nectariferous glands in cyathia quite round, yellowish, with no points.
- Leaves: Alternate, stalkless. Blade elliptic, round-tipped, with entire margin, underside bluish green. Branch leaves narrower than stem leaves.
- Fruit: 5–7 mm (0.2–0.28 in.) long, 3-valved, capsule with fine glands.
- Habitat: Stony, open seashores with hedgerows. Also an ornamental.
- Flowering time: June–July.
- Endangerment: Protected in all of Finland.
Genus Euphorbia is one of the world’s largest genera, containing a legion of different kinds of plants, from annual herbs to trees and cactus-like nectar plants. They comprise a significant part of the vegetation in e.g. the Mediterranean area and Africa – Finnish tourists who escape our harsh winter in the Canary Islands can hardly fail to notice the fleshy-stemmed species that dominate among plants that thrive in dry places, even if they don’t specifically recognize the spurges.
Marsh spurge thrives in the upper part of seashore meadows, growing as much as two metres in height, glowing yellow when it is in bloom and flushing red all over in the autumn. This feast of colour can be admired on the Finnish coast between Hamina and Pellinki – or in gardens where marsh spurge is sometimes grown as an ornamental. Despite its name, the plant thrives in dryish places. Rare and otherwise protected plants should be left to adorn the sea-shore. Also from a selfish point of view it is best to leave them alone because their white latex is highly poisonous and is an external irritant. It causes blisters if it touches the skin and has an even more drastic effect if it comes into contact with mucous membranes or the eyes. Like many other poisonous plants it has been used as a folk medicine – in Finland at least to get rid of warts and calluses.