Euphorbia vulcanorum S.Carter
Euphorbia vulcanorum is a densely branched succulent shrub with green, 4- to 5-angled branches attractively marked with spine shields that bear stout paired spines and form a continuous horny margin along the angles. It grows up to 3.3 feet (1 m) tall and 4 feet (1.2 m) wide. Branches are up to 1 foot (30 cm) long and 0.8 inches (2 cm) thick. The angles are shallowly toothed, with teeth up to 0.6 inches (1.5 cm) apart. The spines are about 0.3 inches (0.8 cm) long. Leaves are soon deciduous, ovate, up to 0.7 inches (1.8 cm) long and up to 0.5 inches (1.3 cm) wide. Flowers are small, showy orangish-red, and appear mainly in spring and fall. Fruits are 3-lobed capsules that are light brownish-yellow flushed with red and have tiny gray seeds.
The specific epithet "vulcanorum (vul-kan-OR-um)" means "fiery" or "of volcanoes or volcanic soils" and refers to the native habitat of the species or its fiery appearance when in bloom. It is an inflected form of the Latin proper noun "Vulcānus," meaning "the god of fire and metalworking."
How to Grow and Care for Euphorbia vulcanorum
Light: This succulent is a sun lover. Place your indoor E. vulcanorum in a sunny window. You may place the pot on the balcony or in the garden from spring to fall. Increase sun exposure gradually to prevent sunburn.
Soil: E. vulcanorum requires well-drained soil. Use a commercial mixture formulated for succulents, or make your own potting mix.
Hardiness: High summer temperatures are not a problem, but low winter temperatures can damage or kill your plant. E. vulcanorum can withstand temperatures as low as 30 to 50 °F (-1.1 to 10 °C), USDA hardiness zones 10a to 11b.
Watering: From spring to fall, water when the top inch (2.5 cm) of soil feels dry. Reduce watering in winter. Give it just enough water to prevent wilting. The best time of the day to water your E. vulcanorum in the warm season is the evening.
Fertilizing: Plants in a pot need regular feeding. Apply a balanced fertilizer in a 10-10-10 NPK formulation, diluted to 1/4 strength once a week during the growing season.
Repotting: E. vulcanorum will benefit from repotting, but it does not need to be repotted every year. When your plant is outgrowing its pot, it is time to repot it in a larger pot and give it a fresh potting mix. The repotting is best done in early spring, at the beginning of the growing season. Wear gloves, protective clothing, and appropriate eye protection when repotting this succulent.
Propagation: The easiest and fastest method of propagation for this plant is by using cuttings. It can also be grown from seeds, but it can be difficult to germinate, even hard to find. The best time to take cuttings is in spring or summer. Sow the seeds in spring.
Learn more at How to Grow and Care for Euphorbia.
Toxicity of Euphorbia vulcanorum
E. vulcanorum produces a toxic white milky sap that can cause irritation to the skin and eyes. Therefore, it is best to keep your plant away from children and pets.
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