Euphorbia unispina N.E.Br.
Euphorbia unispina is a shrubby or tree-like succulent with a thick stem with usually 3 to 4 cylindrical branches and wedge-shaped leaves arranged in a terminal rosette. It grows up to 10 feet (3 m) tall. Branches are silvery-grey, with obscure tubercles arranged in spiral lines and spine shields with a single spine. Leaves are green, often with reddish margins. They are up to 4.8 inches (12 cm) long and up to 1 inch (2.5 cm) wide. The spine shields are up to 0.4 inches (1 cm) in diameter. Spines are dark grey, cone-shaped, and up to 0.5 inches (1.2 cm) long. The older specimens can be spineless.
The flowers (cyathia) are yellow-green, 5-lobed, up to 0.2 inches (0.5 cm) in diameter, and appear at the end of the dry season before the new leaves appear. Usually, the cymes are composed of three cyathia, one terminal and two lateral.
USDA hardiness zones 9b to 11b: from 25 °F (−3.9 °C) to 50 °F (+10 °C).
How to Grow and Care
Euphorbias are very easy to care for. These plants require a little pampering to become established, but once they are, they are self-sufficient. More die from too much care and watering than from neglect. Euphorbias need well-draining soil and lots of sunlight. They are not particular about soil pH but cannot tolerate wet soil. Unlike most succulents, Euphorbia does not handle long periods of drought well. It may need weekly watering during the summer. Water whenever the soil is dry several inches below the surface. Water deeply, but don't let them sit in wet soil, which can cause root rot. Add some organic matter or fertilizer to the planting hole. If you are growing them in containers or your soil is poor, feed them with a half-strength fertilizer monthly.
These succulents can be grown from seed, but they can be difficult to germinate (or even find). They are usually propagated by cuttings. This can be tricky because of the exuding sap. Rooting hormone is recommended with Euphorbias. They tend to grow problem-free, but there are a few pests and diseases to be alert for.
Learn more at How to Grow and Care for Euphorbia.
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