- Name also: Green Spurge, Wolf’s Milk
- Family: Spurge Family – Euphorbiaceae
- Growing form: Perennial herb with subterraneous runners.
- Height: 30–60 cm (12–25 in.). Stem light green–reddish, branches with flowers. Containing latex.
- Flower: Small male and female ‘flowers’ lack a perianth and are borne in groups in the centre of a bowl-like involucre (formed by fused bracts), the whole resembling a single lime green flower. Nectariferous glands in cyathia sickle-shaped, green, with 2 points. Subtending bracts elliptic–ovate in terminal inflorescence, quite round–cordate in branch inflorescence. Stamens numerous. Pistil of 3 fused carpels. Inflorescence a 5–17-branched compound umbel, branches further 2-branched. Underside of terminal umbel with flowering branches.
- Leaves: Alternate, stalkless, lowest small, soon withering. Blade narrowly lanceolate–linear, sharp-pointed, with entire margins, lime green. Branch leaves narrower than stem leaves.
- Fruit: 3 mm (0.12 in.) long, 3-valved, grooved capsule. Fruits explode when mature, spreading seeds up to 5 m (15 ft.)
- Habitat: Field and road banks, railway yards, embankments, waste ground, old gardens, dry meadows.
- Flowering time: June–September.
Leafy spurge is an old established alien in culturally influenced areas which has spread to Finland from the Russian steppes with traffic, the seeds of useful plants and Cossacks. The handsome plant has sometimes been transplanted into gardens as an ornamental. Leafy spurge’s roots reach deep down into the soil and it survives well once it has colonized an area. It spreads efficiently through its subterraneous runners to form dense stands.
Finland’s rare genus Euphorbia plants can be identified by e.g. the amount of rays in the terminal inflorescence, which is many-branched, and is the reason for the plant’s former Finnish name, which means ‘many-rayed spurge.’ Genus Euphorbia plants have a false flower called a cyathium, which is actually the whole small inflorescence. Sepals and tepals are completely lacking, the staminate flower is a solitary stamen, and the pistillate flower is vestigial. One of this kind of pistillate flower and a varying number of staminate flowers, usually five, forms an inflorescence that looks astonishingly like a real flower, and the colourful upper leaves only enhance this impression. Functionally the flowers are no different from real flowers: the colour show provided by the upper leaves attracts pollinators and the nectar at their base is their reward. Leafy spurge’s pollinators, mainly dipterous insects and hymenopterans, are not particularly dedicated to the plant, and it is known to sometimes cross-breed with Cypress spurge (E. cyparissias).
According to the IUCN (International Union for Conservation of Nature) leafy spurge is on a global list of the hundred most harmful foreign species (including plants, animals, insects…).
“Leafy spurge invades prairies, pastures and other open areas. It is a major pest of national parks and nature preserves in the western United States. It can completely overtake large areas of land and displace native vegetation.”
Invasive Plant Atlas of the United States