Euphorbia unispina N.E.Br.
Euphorbia unispina is a spiny, succulent shrub with a stout, sparsely-branched stem up to 13.1 feet (4 m) tall. The branches are usually with a few leaves at their tips and up to 1 inch (2.5 cm) in diameter. They are silvery-grey, covered with shallow tubercles and horny spine shields, up to 0.4 inch (1 cm) in diameter, with a single spine. The flowers are yellow-green, 5-lobed and up to 0.2 inch (0.5 cm) in diameter. There is only one female flower on each cyathium, surrounded by many male flowers. It flowers at the end of the dry season, before new leaves are formed.
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. In fact, 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 they cannot tolerant 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 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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