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Plant of the Month

May 2015

Stenocactus

Stenocactus, or as some people still call it, Echinofossulocactus, seems to be a genus that nobody wants to write about, even though plants can be easily obtained. Echinofossulocactus, which translates from the Latin as a 'furrowed hedgehog cactus', is really quite a good description, even if it is inconvenient to say quickly and to some ears sounds like a joke name. Label writing requires careful judgement to fit in the name before one gets to the end of the label!

Stenocactus was erected in the 20th century first, it seems, as a subgenus of Echinocactus and then as a genus on its own. I have the impression that, to start with, it ran in parallel with Echinofossulocactus but Stenocactus has now been adopted as the name for the genus. 'Steno' is a reference to the thin ribs so frequently encountered in the plants.

Life becomes even more complicated when one turns to species. Almost all members of the genus are characterised by their many thin, wavy ribs but one notable exception is none other than the type species, S. coptonogonus, which has the fewest and thickest ribs of the lot.

By the 1980s a great many 'species' had been named, with plants often very similar to each other and with considerable variability even within populations. Two of my favourites are S. dichroacanthus which lives up to its name and has some very dark and some very light spines, (it is now considered to be a form of S obvallatus). Another, with the field number Lau 1377, has good-sized flowers and eye-catching reflexed spines which, although they look fierce, are fairly flexible and not a hazard when re-potting. This charismatic plant is one that does not seem to be linked with any particular species at present.

So what of the plants themselves, the essence of the hobby, rather than name juggling? They all hail from Mexico and are found at altitudes of up to 2000m, usually single headed, but some will clump with age, both in habitat and in cultivation.

There are no major problems in cultivation and flowering, which usually starts early in the growing season, can be expected from an early age. Colours range through white, with or without a purple midstripe to yellow and purple. Little winter heat seems to be needed although S. coptonogonus tends to mark readily and might need a little more heat. I do not recall seeing red spider mites on any plants but mealy bugs, if around, can find the furrows between the ribs very comfortable.

Stenocacti can have a tendency to become rather woody at the base at an early stage but regular feeding and repotting to keep them moving on can minimise this. Raising from seed is a good prospect but growers should not expect to see multi-ribbed plants from the start, this feature can take a year or two to develop.

Alasdair Glen

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