Euphorbia aka Spurge

Euphorbia is an extremely diverse genus with sizes ranging from tiny ground-hugging annuals to trees reaching 30 meters (98 feet) tall. Most cultivated garden and houseplant varieties typically grow 18 inches to 3 feet tall with a similar spread. Succulent species often grow 1-6 feet tall, while tree forms like Euphorbia ampliphylla can reach impressive heights. Growth rate is generally moderate across the genus. When grown indoors, most species remain compact and manageable.

Temperature requirements vary significantly across the Euphorbia genus. Many garden varieties are fully hardy and can withstand temperatures down to -20°F (USDA zone 5), while tropical and succulent species cannot tolerate frost and need temperatures above 50°F. Most houseplant euphorbias prefer temperatures between 65-75°F during the day with slightly cooler nights. Avoid sudden temperature changes and cold drafts, which can cause stress and leaf drop. In cold climates, tender species should be brought indoors before first frost or grown in protected locations.

Yes, Euphorbia produces unique flower structures called cyathia (singular: cyathium), which are found only in this genus. The cyathium consists of a cup-shaped structure containing tiny male flowers (reduced to single stamens) and a single female flower (reduced to pistil), surrounded by colorful bracts. What appear to be petals are actually modified leaves (bracts) that attract pollinators with their bright colors—typically acid yellow, lime green, red, pink, or white. Flowering occurs mainly in spring and summer, with extended bloom periods. The actual flowers lack sepals and petals but have nectar glands to attract insects.

Notable Euphorbia species include Poinsettia (E. pulcherrima) - the iconic Christmas plant; Crown of Thorns (E. milii) - a popular spiny houseplant with colorful bracts; Pencil Cactus/Milkbush (E. tirucalli) - a striking succulent with pencil-like stems; and Diamond Frost (E. hypericifolia) - an airy annual with tiny white flowers. For gardens, E. characias subsp. wulfenii offers dramatic evergreen structure, while E. griffithii 'Fireglow' provides orange-red spring color. E. amygdaloides var. robbiae excels in dry shade. Succulent enthusiasts value E. obesa (Baseball Plant) and E. horrida (African Milk Barrel). Many varieties have received RHS Award of Garden Merit.

Many Euphorbia species thrive outdoors, with hardiness ranging from USDA zones 5-11 depending on variety. Cold-hardy garden perennials like E. characias and E. polychroma survive winters in zones 5-9, while tropical and succulent species require zones 9-11. For outdoor success, provide well-drained soil and full sun to partial shade. Most species excel in drought-tolerant gardens, Mediterranean landscapes, and xeriscaping. In cold climates, grow tender varieties in containers that can be moved indoors. Avoid waterlogged soil, which causes root rot. Some species like E. cyparissias can spread aggressively by rhizomes and may become invasive in favorable conditions.

Prune Euphorbia after flowering by deadheading spent flower heads or cutting flowered stems back to the base to maintain tidy appearance and encourage new growth. For herbaceous varieties, remove old, brown, dead-looking stems before winter. IMPORTANT: Always wear protective gloves and eye protection when pruning, as the milky latex sap is toxic and causes severe skin irritation and potential eye damage. Rinse tools after use. For shrubby species, take softwood cuttings from short shoots at the base in early spring. Avoid excessive pruning as euphorbias generally maintain good shape naturally.

Repot Euphorbia when roots become crowded, typically every 2-3 years for actively growing plants. Spring is the ideal time, as growth begins. Use a well-draining potting mix—RHS recommends 3 parts peat-free John Innes No. 3 compost mixed with 1 part grit for container euphorbias. Choose a pot only slightly larger than the current one, as euphorbias prefer snug conditions and excess soil retains moisture that can cause root rot. Ensure the pot has drainage holes. Always wear gloves to protect from toxic latex.

Clean Euphorbia foliage by gently wiping leaves with a damp cloth to remove dust, which improves photosynthesis and plant appearance. For succulent species, use a soft brush to clean between stems and remove debris. CRITICAL SAFETY: Always wear protective gloves when handling any part of the plant, as the milky latex sap causes severe skin irritation and potential permanent eye damage. If sap contacts skin, wash immediately with soap and water. If it contacts eyes, flush with water for 15 minutes and seek medical attention. Keep cleaning tools separate and wash thoroughly after use.

Euphorbia propagates through several methods. Division works well for herbaceous clumping types—divide in late spring after flowering or early spring as growth begins. Stem cuttings are effective for shrubby and succulent species: take softwood cuttings from short basal shoots in early spring, let the cut end dry for 1-2 days to prevent rot, then plant in well-draining mix. Seeds can be collected when capsules turn brown and sown fresh. SAFETY: Wear gloves when taking cuttings as latex flows freely from wounds. Dip cut ends in warm water to stop latex flow before allowing to callus.

Common pests include aphids (causing leaf and stem distortion), mealybugs (white cottony masses in leaf joints), spider mites (fine webbing and stippled leaves), and scale insects. Treat with insecticidal soap or neem oil, or wipe off with alcohol-soaked cotton swabs. Major diseases include powdery mildew (white fungal coating on leaves), root rot (from overwatering—often fatal), and rust. Prevent fungal issues by ensuring good air circulation and avoiding overhead watering. Euphorbias are generally trouble-free when grown in appropriate conditions with well-drained soil. Plants are deer and rabbit resistant due to toxic latex.

Euphorbia is pollinated by insects, primarily bees and flies attracted to nectar glands within the unique cyathium flower structure. The cyathium—found only in this genus—contains reduced male flowers (single stamens) and one female flower (single pistil) surrounded by colorful bracts. Unlike typical flowers, euphorbias lack petals and sepals; instead, the bracts serve as visual attractants while nectar glands provide rewards for pollinators. Each cyathium contains multiple tiny flowers, making pollination highly efficient. Fruits develop as explosive three-seeded capsules that split open when ripe, dispersing seeds away from the parent plant.

Euphorbia is NOT edible and should never be consumed. All parts of the plant contain toxic milky latex with diterpene esters that cause severe irritation. Ingestion results in blistering of lips and oral mucosa, nausea, vomiting, and gastrointestinal distress. The latex is caustic and can cause severe damage to mucous membranes. PFAF rates edibility as 0/5 with no known edible parts. Keep plants away from children and pets who might accidentally ingest plant material. Even minor contact with cut surfaces can cause symptoms.

Euphorbia has extensive traditional medicinal uses worldwide, though caution is essential due to toxicity. The latex has been used topically for wounds, warts, and skin cancers—inspiring the modern drug Picato® (ingenol mebutate) from E. peplus for actinic keratosis. Traditional applications include treatment for respiratory ailments (asthma, bronchitis), parasitic infections, gastrointestinal complaints, and fever. However, as of 2019, no rigorous clinical evidence confirms effectiveness for any disease. The toxic latex requires expert knowledge for safe use. Self-medication is dangerous and not recommended. Always consult healthcare professionals.

Beyond ornamental value, Euphorbia has diverse practical applications. Ornamentally, the genus includes major commercial plants like Poinsettia (holiday decoration) and Crown of Thorns (houseplant). Succulent species are prized for drought-tolerant landscaping and xeriscaping. E. antisyphilitica (Candelilla) yields valuable wax used in cosmetics, polishes, and candles. Some tree species provide soft wood for furniture, musical instruments, and fuel. Burnt wood has been used in traditional gunpowder production. Modern interest includes biofuel research due to latex hydrocarbon content. The latex itself serves as a natural adhesive in some applications. Plants are valuable for ecological gardens as they're deer and rabbit resistant.