by Bruce Brethauer
Euphorbia decaryi var spirosticha is a wonderfully compact variety, eventually producing a densely branched, spreading plant, usually measuring to only a few inches in height (individuals with more upright branches are said to grow to about 12 inches high) and with low, nearly horizontal branches spreading to a foot or more in older plants. This species spreads by underground stolons, so that plants growing on unrestricted open ground, can eventually produce a multi-tufted plant with a spread of at least several feet across. The branches are typically long and narrow, growing to perhaps 8 mm in diameter and growing to several inches or more in length. The stems are tightly spiraled, (accounting for its varietal name, spirosticha) and look to be more or less cylindrical in shape. These are intricately textured with stipular prickles along the edges of its numerous leaf bases. The stems can vary in color from a purplish mahogany-brown to grey depending upon its age and growing conditions. Each stem bears a small tuft of remarkably ruffled, succulent leaves. The leaves are typically small, usually measuring to an inch or less in length. Plants which are grown in very bright light tend to produce leaves tinged with rusty purplish brown tones, while plants which are grown under somewhat lower light levels will produce green leaves. Plants will only maintain a few leaves on each of its branch tips. Plants which are grown under somewhat moister conditions may retain a few extra leaves on each stem, but not dramatically so. The cyathium are minute, with nodding, cuplike, mauve bracts, and yellow/green anthers and pistils. The flowering portions are so small that they often are unnoticed: no-one grows this plant for its showy flowers.
Euphorbia decaryi var spirosticha comes from the Didierea-Alluaudia forest (the so called Thorn Forests) in Southern Madagascar. It is listed under CITES Appendix 1, indicating that this species and its varieties are critically endangered - being at the edge of extinction in the wild. But paradoxically, this is one of the more commonly grown varieties of the Madagascan Euphorbias, proving to be both forgiving and adaptable: in my experience, it is very easy and amendable in cultivation, and is readily available from most mail order nurseries specializing in succulents, and may occasionally 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, E. cylindrifolia and their varieties. All are compact plants which are highly collectible, often regarded as succulent "bonsai"; but to my tastes, this is one of the best plants of the entire 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. But 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. This has not been my experience - in fact, plants grown outdoors through the summer months have thrived through our summer rains. Perhaps the secret is to choose the proper potting medium - one which does not retain water for very long, and which retains lots of air pockets throughout. This past year, I have had very good results growing this plant in Moo-Nure, a soil amendment composed of composted forest debris and cow manure - while this may sound as though it is far too high in organic materials, I have found its ability to dry rapidly - even after it has been thoroughly saturated with water - to be especially valuable when growing succulents. It is widely available (in Central Ohio, it is carried by all Home Depots) and it is inexpensive.
This variety really appreciates warm summer temperatures, and so this plant should be moved outdoors every summer to benefit from the increased temperatures, and light. While this plant can and does survive some pretty chilly temperatures (down to nearly freezing) it really should be maintained at comparatively warm temperatures through the winter months - it is probably best maintained at temperatures to 55 degrees or warmer in winter. While plants can eventually grow to several feet in diameter, plants which are kept in small containers can be maintained at much smaller sizes for long periods: I have seen plants grown in small bonsai pots remain compact and tidy for over 10 years. Plants which are provided with larger containers, or which are frequently re-potted will tend to spread faster to produce larger plants. Once you have grown a plant to nearly the desired size, keep it underpotted to maintain its size for a longer period of time. Eventually it may outgrow its allotted space, but this plant can be readily grown from stem cuttings, and also from cuttings taken from its stolons. In either case, cuttings are best taken in spring or early summer when the plant is showing good growth. I have always grown this plant from small cuttings - about 2 inches of the stems has been enough to get a start of this plant. After the cuttings have been taken, set them aside for a week or so for the cut ends to heal, and then insert the cut ends into barely moist potting medium in a warm place, under indirect bright light. In my experience, the first roots will usually set within a few weeks, and new leaves will be produced soon afterwards. I'm sure that you can start with a larger cutting to establish a reasonably sized plant faster, but I cannot comment on whether or not larger cuttings take any faster, or produce more growth in their first seasons.
Seeds or cuttings? When I first began to grow this plant (more than 20 years ago), the prevailing wisdom of the time was that a plant grown from cuttings would probably not produce typical growth, so the recommendation at that time was to grow plants from seed. In my experience, it is easy to produce typical plants from cuttings, so this is probably the easiest method for most hobbyists to propagate additional plants. For those growers who have the patience and acute eyesight to pollinate the flowers and harvest the seed (etc.), seed grown plants may offer certain advantages, (genetic recombinations which could potentially result in plants with new and desirable traits, or the potential for faster, vigorous growth due to the increased vigor of seedlings), but in my opinion, it is so much easier to grow these plants from cuttings, that there is little reason to grow these from seed.
As with all things in the realm of succulents, beauty is in the eye of the beholder with this plant. I really admire the appearance of the tightly spiraling branches with their textured leaf scars and bracts, and am especially fascinated by the ruffled leaf edges: other growers like the Spartan look of this plant, with its small tufts of leaves at the ends of long, otherwise bare stems - it speaks of the tenacity of a survivor which has endured decades of hardship. Those who are somewhat less appreciative of succulents may see a plant which seems to be at death’s gate: a plant virtually stripped down to bare branches with a sparse remnant of contorted leaves: I guess that there is no accounting for taste. In either case, if you grow this plant, I think that it is a good idea to keep a magnifying glass handy - this will help you better appreciate some of the smaller features of this plant - and may assist some growers in locating its small cyathea. It may also be useful in discovering early signs of pest infestations: while this plant is not particularly susceptible to pests (in my experience, it has proven to be quite resistant to insect infestations) it is not immune. Always keep a lookout for mealybugs and spider mites. The dense branching and highly textured stems can conceal these pests until their populations have grown considerably. Also, whenever transplanting or repotting, inspect the roots of this plant for evidence of root mealy bugs. Treat infested plants promptly with an appropriate insecticide, and isolate the plant during treatment, lest these pests migrate to other plants in your collection. In smaller infestations, repeated applications of an insecticidal soap may prove to be adequate (these soaps work on contact with insects, so make sure that you spray the plant thoroughly to treat all of the plant's surface). Heavier infestations may require stronger measures - such as a powerful systemic insecticide. Whenever using insecticides, always follow the instructions carefully. All pesticides are potentially hazardous, and many are not suitable for household use.
These concerns aside, I find Euphorbia decaryi var spirosticha to be a nice, compact plant with a lot of character, and few downsides. Plants can be maintained in small bonsai pots for many years, without outgrowing their allotted space. Their growth habit is reminiscent of a low and spreading bonsai tree, and their densely ruffled succulent leaves are truly distinctive. They offer few challenges, and have proven to be forgiving, and adaptable. If you are developing an interest in succulent bonsai, this plant would be an excellent choice.