Petty spurge
Also known as
Radium weed, Little spurge, Milkweed, Cancer weed
Keep this plant’s care guide close at hand.
Get the appAbout Petty spurge
Euphorbia peplus, commonly called petty spurge, is a small, soft, annual herb in the spurge family native to Europe, North Africa, and Western Asia, now naturalized on most continents. It grows 5–30 cm tall with smooth, branching green stems and oval, soft leaves. Its tiny greenish-yellow cyathia (specialized Euphorbia flowers) appear from spring through fall, producing three-lobed capsules that explosively disperse abundant seeds. The plant exudes a white, milky latex when cut, which is strongly irritant to skin and eyes and toxic if ingested. In cultivation it thrives in disturbed, well-drained soils and cool to mild conditions, often volunteering in garden beds, pots, and paths. While sometimes intentionally grown for study or as a companion in wildlife-friendly plots, it is more often considered a self-seeding weed. Handle with gloves, site away from children and pets, and prevent unwanted spread by deadheading before seed set. Note: historical folk use and pharmaceutical interest in its compounds do not make it safe for home medicinal use.
Taxonomy
Properties & Requirements
How to care for Petty spurge
Water
Water to keep the soil lightly moist but never waterlogged. Outdoors, natural rainfall often suffices; irrigate only during extended dry spells. In containers, allow the top 1–2 cm (½–¾ in) of the mix to dry between waterings, then water thoroughly until excess drains. Reduce frequency in cool weather and avoid wetting foliage before intense sun to minimize scorch. Though somewhat drought-tolerant once established, consistent, moderate moisture yields a compact plant and reduces premature seeding.
Light
Provide bright light: full sun to partial shade. In temperate climates, 4–6+ hours of direct sun promotes compact growth and flowering. In hotter regions or reflective urban sites, aim for morning sun with light afternoon shade to prevent stress and excessive transpiration. Too much shade causes leggy, weak stems and reduced vigor. If grown indoors short-term, place at a bright south or east window, rotating for even light.
Nutrients
Petty spurge is adapted to relatively lean, disturbed soils and generally needs little to no fertilizer. Overfeeding, especially with high nitrogen, encourages weak, sappy growth and heavier self-seeding. For container-grown specimens, mix in a modest amount of compost at planting and, if needed, apply a balanced, dilute liquid fertilizer (e.g., 1/4-strength 10-10-10) once monthly during active growth. Avoid fertilizing in mid-summer heat or during dormancy/decline. Good soil structure and drainage matter far more than nutrient richness.
Temperature
Best growth occurs in cool to mild conditions, roughly 10–24°C (50–75°F). It is frost-sensitive; protect from freezes and avoid planting out until danger of frost has passed. In hot weather above ~29–32°C (85–90°F), plants may wilt, bolt, or decline; provide afternoon shade, mulch, and adequate moisture to mitigate heat stress. Indoors or in protected frames, ensure good airflow to prevent fungal issues in cool, humid spells.
