Plant Highlight: Euphorbia resinifera
Among the succulent Euphorbia species, some look remarkably cactus-like, and are often mistaken for cacti by those not familiar with them. One such plant is Euphorbia resinifera, which comes from the slopes of the Atlas Mountains in Morocco.
Euphorbia resinifera forms a mound of chubby columnar stems which expands over time, with the tallest central stems reaching a height of 2 to 2½ feet (.6 to .75 m). An old clump may be several feet wide (more than a meter). Each stem is four-sided, with a row of small spines extending up along each corner. The stems are green to gray-green in color and up to 1.4 inches in diameter (3.5 cm).
Some sources give the flowering time for Euphorbia resinifera as late winter to early spring, but at the Ruth Bancroft Garden our plants typically come into flower in mid-May to early June. Plants in the genus Euphorbia have a specialized flowering structure called a cyathium (plural – cyathia), consisting of a cup with glands around the outside and small flowers in the middle. In the case of Euphorbia resinifera the glands are yellow-orange in color, and the little flower at the center is a paler greenish-yellow.
E. resinifera is not a demanding plant, needing only a spot with good drainage and sun. It will do fine in partial shade, but is at its most compact in a sunny position. It can endure winter lows down to 20° F (-7° C).