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Euphorbia persistens

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by Bruce Brethauer

Euphorbia persistens

           I have been a long time grower of the succulent euphorbias; I am especially drawn to those species with exceptional forms, highly patterned stem markings, and unusually colorful or interesting spines. Over the years, space considerations, and the growing requirements of many of my euphorbias (some do not fare well through a cool winter dormancy), I have been forced to pare down my collection to a relatively few plants. Euphorbia persistens is one of those few euphorbias which remain in my collection. This species has hit all of my "points"; first of all, it is long lived, and easy to grow, tolerating a wide range of growing conditions;  it is a relatively compact plant, producing densely branched mounds of succulent, and curiously twisting stems from a thick taproot (some growers may even opt to raise the root to expose it). While the root is a good size, I am not certain that I would regard this plant as a caudiciform. Young plants have carrot-like roots, I believe that as the plant ages, the roots may thicken, and may become more beet-like in their general shape. The stems are attractively marked - typically in light and dark green, but when grown in full sun, may take on more earth-toned or rusty hues. The spines are initially colorful, with new growth emerging almost a hot pink, and fading, first to amber/brown, and finally to a pale grey. The stems have the rudiments of a corkscrew twist, which is not quite as pronounced as it is in its close relative, Euphorbia tortirama. Interestingly, a percentage of these stems may actually twist one direction in one growing season, and may reverse direction in a subsequent growing season.

           I could not locate any photographs of the cyathia on my plant, but I recall that these were bright yellow, and contained both male and female flowers. In my experience, the flowers readily self, and frequently produce viable seed.

           This is an easy plant to propagate, the plant in these photos had been grown from seed set on the plant which I had purchased from The Glasshouse Works, but plants can also be easily grown from stem cuttings. Unlike many species of euphorbia, this plant will produce typical growth - including the characteristic tap root, and clustering stems on plants which have been propagated from cuttings.

           This plant responds very well to my to my basic guidelines on growing cacti and other succulents, with a few additional considerations. First of all, because of the thick taproot, this plant will require a somewhat deeper pot, and will benefit from especially sharp drainage. It would probably be best to give this plant a 1 or 2 inch top dressing of gravel to keep the crown dry. Whenever transplanting, or repotting, make sure that you do not bury the crown any deeper than it was originally planted (you may opt, however, to raise the crown somewhat, to partially expose the root, and as a precaution against crown rot). This is another species which really thrives when moved outdoors to benefit from hot summer temperatures and increased exposure to full sunlight. Grown outside through the warmer months of spring through early fall, my plants have always rewarded me with a good flush of growth; adding multiple new stems each season. While this plant is quite tolerant of a huge range of temperatures - my plants having survived temperatures down to the high 30's (Fahrenheit), it does not appreciate an extended cool dormancy - during its dormancy, it would probably be best to maintain temperatures at or above 60 degrees Fahrenheit (I maintain my plants at cooler temperatures during their dormancy, but they show some distress by the end of winter).

           This plant is not for every grower; it is exceptionally spiny, with stout and rigid spines. Like all of the euphorbias, this plant produces a milky sap which can be irritating, if not outright toxic. While none of my cats have been curious enough to investigate this plant, not all pets can be trusted around houseplants.

       As with most of the succulent euphorbias, the individual flowers are small, so if you are only interested in plants with large, brightly colored flowers, this plant will not satisfy you.

           This plant is not widely available: I have never seen it offered at any of the "Big Box" nurseries, and it is only infrequently offered through some of the specialist mail order nurseries. Plants of this species may come up from time to time at area CSSA shows and sales. I acquired my plant through The Glasshouse Works, but I believe that it has also been offered at the following nurseries:

       Arid Lands
       Out of Africa
       If you are interested in one of the more decorative, and curious members of the succulent euphorbias, seriously consider this species.

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