Euphorbia marginata aka Snow On The Mountain

Euphorbia marginata, or snow on the mountain, belongs to the spurge family. This annual comes from west-central and central America’s United States through eastern and southern Mexico. It grows in prairies, pastures, roadsides, and disturbed ground. Garden plants have escaped across many other US states. Its white-edged leaves explain the name snow on the mountain.

Plants grow upright, reaching about 1–3 feet [0.3–0.9 metres]. RHS gives an upper height of 3.3 feet [1 metre]. They spread about 1–2 feet [0.3–0.6 metres]. A single main stem supports the plant, with branching near its top. Young stems have white hairs, which disappear as stems age. Their green colour shifts toward yellow or reddish brown. The oval leaves have pointed tips and no stalks. Upper leaves gain broad white edges as the season moves on. Some turn white across the whole blade.

Flowers appear from July to September at the stem tips. The small, greenish-yellow flowers lack petals and form cup-shaped groups called cyathia. Each group holds male flowers around one female flower. White bracts provide most of the display and last well. Bees and other pollinators visit the flowers. The fruit forms a small capsule with three sections. Dense white hairs cover its surface. It changes from green to dark grey and holds three ridged seeds.

Give this plant full sun and soil that drains well. Some afternoon shade helps where summers are hot. Too much shade can leave the stems weak and floppy. It accepts poor soil, clay, loam, sand, and rocky ground. Acid, neutral, and alkaline soils all suit it. It tolerates drought and needs dry to moderately moist conditions. Grow it from seed in spring; plants can also seed themselves. Sources list USDA zones 2–11 for this annual. RHS rates it H2, so it does not survive freezing.

Use it in borders, meadows, containers, or cutting gardens. It also suits sunny, dry ground as an annual cover. Deer and rabbits tend to leave it alone. Serious pests and diseases are few, though aphids may cause trouble. Self-seeding can make it weedy. Its milky sap can inflame skin and harm the eyes. Wear gloves and keep plants away from children and pets. All parts are unsafe to eat, including dried material. PFAF records chewing latex and folk remedies, but also warns of toxicity. These records do not make it a safe food or home treatment.