- Name also: Madwoman’s Milk
- Family: Spurge Family – Euphorbiaceae
- Growing form: Annual herb.
- Height: 15–40 cm (6–16 in.). Stem often base branched, sparsely hairy. Containing latex.
- Flower: The 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 elliptically round, green, with no points. Subtending bracts obovate, like stem leaves. Stamens numerous. Pistil of 3 fused carpels. Inflorescence a 5-branched compound umbel, branches first 3-branched then 2-branched.
- Leaves: Alternate, lowest opposite, almost stalkless. Blade obovate, with blunt or notched tip, tip finely serrated, lime green.
- Fruit: About 3 mm (0.12 in.) long, 3-valved, glossy, glabrous capsule.
- Habitat: Gardens, vegetable patches, fields, soil heaps, waste ground.
- Flowering time: July–September.
Genus Euphorbia is one of the largest groups of vascular plants and its representatives are found all over the world, everywhere but the coldest places. The genus includes a hugely diverse range of species, from annual herbs to large trees, and the inflorescence of its members has specialized in the peculiarities of the natural architecture over a long period of time.
Sun spurge is one of the more common of the small amount of genus Euphorbia species that grow in Finland. The plant’s former Finnish name refers to the way its latex was used to treat dry, flaky eczema that was caused by parasitic fungi. Like its relatives, its latex is notably poisonous, so it is best to forget experimenting alone with its medicinal properties. When the plant is carefully watched, it can be seen that it turns its beautiful flowering stems towards the sun. This was also apparently noticed by the botanists who named it: its scientific name helioscopia comes from the Ancient Greek helios, ’sun’ and skopein, ’to watch’: sunwatcher!
Sun spurge is most likely found in fields and gardens, and its appearance is to a certain extent tied to old inhabitation. Its habitats are often shared by petty spurge (E. peplus), which has a three-branched inflorescence and full leaf blades which have entire margins.