Crown of Thorns

Euphorbia milii is endemic to the island of Madagascar, off the southeastern coast of Africa.

• Native to the central and southern highlands of Madagascar
• Found at elevations of approximately 200 to 1,500 meters
• Grows in dry, rocky thickets, on limestone outcrops, and in spiny forest habitats characteristic of Madagascar's arid southwest
• Madagascar is one of the world's most biodiverse islands, with over 90% of its flora found nowhere else on Earth
• The island is home to approximately 170 Euphorbia species, many of which are endemic and threatened
• First described by the German botanist Johann Jakob Bernhardi in 1826, based on plants grown from material sent by Baron Milius
• Has been cultivated in European greenhouses since the 1820s and is now naturalized in many tropical regions worldwide
• Particularly common in cultivation in Thailand, where extensive hybridization has produced hundreds of named cultivars with large, showy bracts
• Naturalized in parts of Brazil, the Caribbean, India, Southeast Asia, and tropical Africa

Euphorbia milii is a woody, much-branched, succulent shrub with formidable thorns.

Stems:
• Erect to scrambling, woody at the base, succulent toward the tips
• Typically 30 to 100 cm tall in cultivation, occasionally reaching 150 to 200 cm
• Covered with stout, sharp thorns 1 to 3 cm long, arranged in pairs at each leaf node
• Stems are grayish-brown to green, roughly 5 to 15 mm in diameter

Leaves:
• Obovate to spoon-shaped (spatulate), 2 to 6 cm long and 1 to 2.5 cm wide
• Bright green, fleshy but relatively thin for a succulent
• Produced mainly on new growth; older stems often drop their leaves, becoming bare and thorny
• Leaves are deciduous during periods of drought stress

Flowers (cyathia):
• The true flowers are tiny, greenish-yellow cyathia approximately 5 to 8 mm across
• Each cyathium is surrounded by a pair of large, showy bracts (cyathophylls) that are the colorful part most people recognize as the "flower"
• Bract colors: most commonly bright red or scarlet, but cultivars exist in pink, salmon, yellow, white, orange, and bicolor combinations
• The large-flowered Thai hybrids (often sold as Euphorbia milii var. splendens or E. x lomi) have bracts up to 5 cm across
• Blooms nearly continuously in favorable conditions, with peaks in spring and autumn

Fruit:
• Small, three-lobed capsules approximately 5 to 8 mm in diameter
• Green ripening to brown; explosively dehiscent when mature, launching seeds up to several meters

The milky latex sap of Euphorbia milii is toxic and irritating.

Toxic compounds:
• Contains diterpene esters (phorbol esters and others) that are potent irritants
• The latex is a known co-carcinogen and tumor promoter

Skin contact:
• Fresh sap causes immediate burning, redness, and blistering on sensitive skin
• Prolonged contact can cause severe contact dermatitis
• Wash affected areas thoroughly with soap and water

Eye contact:
• Sap in the eyes is a medical emergency — causes intense pain, corneal damage, and potential vision impairment
• Seek immediate medical attention if eye exposure occurs

Ingestion:
• Causes burning of mouth and throat, nausea, vomiting, abdominal pain, and diarrhea
• The toxic compounds affect mucous membranes throughout the digestive tract
• Keep away from children and pets

Safety precautions:
• Wear gloves and eye protection when pruning or handling
• Wash hands thoroughly after contact
• The thorns themselves can cause painful puncture wounds that may become infected
• In some individuals, even thorn pricks can introduce latex into the wound, causing localized irritation

Crown of Thorns is one of the toughest and most adaptable flowering houseplants.

Soil:
• Requires well-drained soil — a cactus/succulent mix or sandy loam with added perlite or pumice
• Tolerates a wide pH range from slightly acidic to slightly alkaline

Light:
• Full sun to bright indirect light — the more light, the more flowers
• In low light conditions, flowering decreases dramatically and growth becomes leggy
• A south or west-facing window is ideal indoors
• Outdoors, tolerates full sun in hot climates once established

Watering:
• Water thoroughly, then allow the top half of the soil to dry before watering again
• Highly drought-tolerant — can survive weeks without water, though flowering may pause
• Overwatering causes root rot; underwatering causes leaf drop (leaves regrow when watering resumes)
• Reduce watering in winter but do not let the soil dry to the bottom of the pot for extended periods

Temperature:
• Thrives between 18 and 32°C
• Damaged by prolonged exposure below 10°C; will not survive frost
• Suitable for USDA hardiness zones 10 to 12; widely grown as a houseplant in cooler zones

Fertilizer:
• Feed monthly during the growing season with a diluted bloom fertilizer (higher phosphorus)
• Withhold fertilizer in winter

Pruning:
• Prune to shape and control size, wearing heavy gloves to protect against thorns
• Cut stems back to a node or branching point; new growth will emerge from below the cut
• Caution: pruning releases copious toxic latex — protect eyes and skin
• Propagate from stem cuttings, allowing the cut end to callus for 3 to 5 days before planting