Houseplant
African Milk Tree
Euphorbia trigona · Euphorbiaceae
Also called: Candelabra Euphorbia, Cathedral Cactus, Friendship Cactus, Abyssinian Euphorbia
African Milk Tree (Euphorbia trigona) is a very low-water houseplant well suited to Tucson and the low desert.
African Milk Tree at a glance
- Water use
- Very Low (established)
- Sun
- Bright indirect light indoors; tolerates some direct morning sun. If grown outdoors in Tucson, give bright shade to filtered light and protect from intense afternoon/reflected sun, which scorches the stems.
- Mature size
- Indoors/container typically 3-6 ft tall; can reach 6-9 ft in ideal conditions, upright candelabra form, slow to moderate spread.
- Growth rate
- Moderate (fast for a succulent when warm and well-lit).
- Bloom
- Rarely blooms in cultivation; flowers insignificant. Grown for upright green (or 'Rubra' reddish-purple) ridged stems., Rarely flowers indoors.
- Cold hardiness
- Frost-tender; damaged below about 50F and killed by frost. In Tucson it must be grown indoors or in a protected container that is moved inside whenever nights approach freezing. Minimum comfortable indoor temp ~55-60F.
- Soil
- Fast-draining cactus/succulent mix; add perlite or pumice. Must never sit in soggy soil. Container needs drainage holes.
- Native range
- Central Africa (Congo region / West-Central Africa)
- Best used as
- Architectural houseplant / specimen, Container accent on protected patios, Vertical sculptural form for modern/xeric interiors
- Wildlife
- No notable wildlife value; latex deters herbivores.
- Toxicity
- Highly toxic and irritating. The milky latex causes severe skin, eye, and mucous-membrane irritation/burns and is poisonous if ingested - hazardous to pets and children. Wash exposed skin immediately and keep away from eyes.
How to grow African Milk Tree in Tucson & the low desert
Watering
Indoors, water only when the potting mix is fully dry, roughly every 2-3 weeks in summer and monthly or less in winter. It is very drought tolerant and far more often killed by overwatering/rot than by drought.
Fertilizer & nutrients
Light feeder. Apply a dilute balanced or cactus fertilizer (half strength) once monthly during the warm growing season (spring through early fall); do not feed in winter.
Pruning & care
Prune only to control height or shape, in spring/summer. ALWAYS wear gloves and eye protection - cut stems ooze copious toxic white latex. Let cuttings callus before rooting.
Notes
Not a true cactus despite the 'candelabra/cathedral cactus' nicknames - it is a succulent Euphorbia. In Tucson's low desert it is best treated as an indoor/protected container plant because it cannot survive winter frost outdoors. Handle with care due to caustic latex.
Sources: University of Arizona Cooperative Extension (general Euphorbia/succulent guidance); Arizona-Sonora Desert Museum (succulent culture); New York Botanical Garden houseplant care guide (Euphorbia trigona); Gardenia.net plant database