Euphorbia trigona
| Light | Bright light to a few hours of direct sun; tolerates light shade indoors |
|---|---|
| Water | Moderate in growth; let the top of the mix dry out, and water sparingly in winter |
| Soil | Free-draining succulent mix with plenty of grit (see Soil and potting mix) |
| Temperature | Keep well above freezing; USDA zones 10–11, or as a houseplant |
| Propagation | Stem cuttings (easy); allow the cut latex to seal and callus first |
| Toxicity | Toxic — the milky latex is a skin, eye and mucous-membrane irritant; keep away from pets and children |
Euphorbia trigona, the African milk tree, is a fast-growing, upright, branching succulent with distinctly three- to four-angled stems that is one of the most widely sold "cactus-like" houseplants in the world. Despite its cactus appearance it is a true Euphorbia, not a cactus, and — like others in the genus — it bleeds a milky white latex when cut. It is especially popular in its red-tinged Rubra (also sold as Royal Red) form.
Description
Euphorbia trigona forms an erect, candelabra-like plant of upright green stems that branch from the sides to build a dense column over time; in the ground and given years it can reach a couple of metres, though as a pot plant it usually stays much smaller. The stems are sharply ridged with three (sometimes four) winged angles, and along the edges sit paired short spines together with small, spoon-shaped leaves that emerge on new growth and later drop.
The green form is marbled with paler bands down the ridges. The popular Rubra/Royal Red form flushes deep burgundy-red across the stems and leaves, especially in bright light. Flowers are rarely seen in cultivation and are small and inconspicuous when they do appear.
Every part of the plant contains a copious white latex that flows freely from any wound. This sap is irritating to skin and eyes and toxic if ingested, so gloves and eye protection are sensible whenever cutting or repotting.
Distribution and habitat
The species is generally attributed to Central and West Africa and has an unclear wild origin; it is very widespread in cultivation but poorly documented as a truly wild plant. In warm, frost-free climates it is grown outdoors as a fast hedge or specimen, while in cooler regions it is a common indoor plant.
Cultivation
Euphorbia trigona is one of the easiest succulents to keep and a good beginner plant, provided it is not overwatered. Grow it in a free-draining succulent mix in a sturdy, well-weighted pot — a tall plant can become top-heavy. Give it bright light; a few hours of direct sun will keep growth compact and, in the Rubra form, deepen the red colour, while too little light produces thin, pale, stretched stems.
Water moderately during the warm growing season, letting the top of the mix dry between waterings, and cut back sharply in winter when the plant rests. See Watering and Repotting for general technique. Because the stems are tall and shallow-rooted, staking or a heavy pot helps prevent toppling. Take particular care with the latex: work in gloves, protect your eyes, and keep the plant out of reach of pets and small children.
Propagation
Propagation is easy from stem cuttings. Cut a branch cleanly, then rinse or blot the cut end to stop the flow of latex and let it dry and callus for several days to a week before setting it in a dry, gritty mix to root. Handle cuttings with gloves. See Propagation — cuttings for a full walkthrough.
Common problems
- Rot — the most common killer, almost always from overwatering or a slow-draining mix; the base softens and browns.
- Etiolation — insufficient light gives thin, weak, over-stretched stems and, in Rubra, loss of red colour.
- Toppling — tall plants in light pots fall over; use a heavy container or a stake.
- Pests — mealybugs (white fluff in the ridges and leaf axils) and, in dry indoor air, spider mites.
See also
- Euphorbia — the genus overview
- Propagation — cuttings · Soil and potting mix · Watering · Repotting · Pests and diseases