by Bruce Brethauer
Euphorbia cylindrifolia v tuberifera is one of the most distinctive and bizarre of the miniature Euphorbias from Madagascar; it produces a partially buried irregular caudex which may grow to about the size of a fist, with many nearly horizontal branches radiating from it. The stems are textured with leaf scars and minute stipular prickles, and are tipped in clusters of small succulent leaves which are grooved on their upper surfaces. These leaves are small, about 1/2 inch or so in length. These leaves are tough and often persist over several seasons. Leaf color can vary from dark green to purplish brown depending upon light intensity, and whether or not the plant is stressed due to drought or other factors (plants which are maintained at moister levels tend to have greener leaves which tend to persist on the plant: plants which are subjected to extended drought or which are grown under very bright light will tend to have browner leaves, and may only maintain a few leaves at the stem tips).
The flowers (cyathium) are quite small, and are enveloped by nodding grey to yellowish-pink cyathophylls, which partially enclose the cyathium. The actual cyathium are minute - only a few millimeters across, and are best viewed from below. The downward oriented small "flowers", which are held low on the plant would suggest that ants probably play an important role in the pollination of these flowers. While this variety can be propagated from stem cuttings, such plants may never produce the characteristic caudex - only seed raised plants will produce a caudex.
Euphorbia cylindrifolia v tuberifera comes from the Didierea-Alluaudia forest (the so called Thorn Forests) in Southern Madagascar. It is listed under CITES Appendix 1, indicating that this variety is critically endangered - being at the edge of extinction in the wild. But paradoxically, this is a rather popular plant amongst cactophiles and growers of succulent "bonsai" and is one of the more commonly grown varieties of the caudiciform Euphorbias. It is readily available from many mail order nurseries specializing in succulents, and may also be available through companies offering plants suitable for bonsai.
This plant is closely allied to a complex of other Madagascan species which includes E. francosii, E. cap-saintemarienensis, and E. decaryi and their varieties. All are compact plants which are highly collectible, often regarded as succulent "bonsai". This variety is closely related to variety cylindrofolia, but differs in having a large caudex - also, variety tuberifera does not spread by undergorund stolons. This is one of most curious and interesting of the group. I have found it to be an easy plant to maintain in cultivation, responding quite well to my basic guidelines for growing cacti and other succulents. As with all Madagascan Euphorbias, this plant grows best at warmer temperatures (in my experience from the lower 80's to about the mid 90's during its growing season) and very bright light. It responds especially well to life on the patio during the summer months. While I have found this plant to be comparatively easy to grow, in researching this variety online, I have found a number of growers who have had difficulties with this plant, citing that their plants have proven to be sensitive to excess water. During its growing season, my plant appreciates frequent watering, and does not seem to be rot prone - however, during its winter dormancy, I am careful to make sure that this plant is not overwatered - I rarely water my plants more than once every 4 to 6 weeks in winter. This plant is sensitive to extended periods of cold, and is especially prone to rotting when it is exposed to cold during its winter dormancy. A potting medium with sharp drainage is essential, as is a warm growing season, and very bright light. While I would not say that this plant is any more susceptible to to infestations of mealy bugs than other euphorbias, in plants of this variety with lots of foliage and particularly dense branching, the presence of mealy bugs can go unnoticed until their numbers have increased to dangerous numbers. It is especially important to inspect plants for early signs of problems and take any necessary corrective measures as soon as possible. Healthy plants seem to be resistant to insect problems, so the presence of mealy bugs may also be an indicator of less than optimum growing conditions, and may suggest a change in the plant's growing conditions is called for. (after the mealy bugs have been eradicated).
My greatest reservation with this variety is that it is a S L O W G R O W E R. Even under the best of circumstances, growth is ponderous, so expect to wait many years to produce an impressive specimen. On the other hand, it will take a very long time for this variety to outgrow its allotted space. A seedling fits comfortably in a very small bonsai pot. A shallow bonsai pot may also make the caudex "self rising": as the caudex expands downward to the bottom of the pot, it may push the plant upwards as the caudex grows.
This plant is not for every grower - The appearance of the plant is more curious than beautiful, and frankly, a well grown plant may have the appearance of a beached octopus, - often inducing novices to ask "Is it supposed to look like that?" Those of us who know and grow this plant appreciate it for its strange form, and that world-weary look of a true survivor. If you are looking for a plant with more beautiful lines or showy flowers, this is not the plant for you, nor is if for the impatient. It has a great appeal to those growers who already have an interest in the caudiciforms, and for growers of natural bonsai. If you have an interest in growing some of nature's more unusual plants - give this plant a try.
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