Understanding Stenocactus

[BarryRice]

Hey guys

I'm trying the mad task of understanding a little more about the species in this genus, especially as I have several in my collection.

I know this is in part a foolish task, as hybrids may exist in cultivation, but I'm not giving up so quickly!

My first question regards S. phyllacanthus. I just read with surprise, in "Ariocarpus et cetera," that this species has yellowish flowers, a statement supported by the images in my copy of "The New Cactus Lexicon Illustrations." This is NOT supported by the images in CactiGuide and other online resources.

What gives?

[iann]

I suspect there aren't many cacti mis-labelled more often than Stenocactus

[DaveW]

I tried for years to find an effective key to Stenocactus species and then gave up! You would need to consult the original description of S. phyllacanthus to find original flower colour. Remember David Hunt is a "lumper" in the NCL so maybe he has lumped yellow and other flower coloured forms as synonyms and illustrated the plant with a yellow flowered form?

As to yellow flowered forms. You find them under various names:-

viewtopic.php?t=16290" onclick="window.open(this.href);return false;

http://davesgarden.com/guides/pf/showimage/270479/" onclick="window.open(this.href);return false;

http://magicactus.com/fcc_stenocactus.html" onclick="window.open(this.href);return false;

http://www.llifle.com/Encyclopedia/CACT ... aupelianus" onclick="window.open(this.href);return false;

Spination seems very variable in Stenocactus and I wonder how representative what we grow as distinct species in cultivation are of the variation of the species in habitat, or are many simply selected clones of the same species? It's certainly a genus that requires far more work in the field.

[phil_SK]

There is a quite detailed review of the many names published in CSJGB 1979, 41(2), 35-42. Mention is made of some of the inconsistencies in S. phyllacanthus's descriptions over the years, including flower colour. There's even a key to the main species. It certainly a good place to start if you're wanting to get your head round things. You can download it from http://cactuspro.com/biblio/en:csjgb" onclick="window.open(this.href);return false;

[peterb]

There are two forms of phyllacanthus (at least!) that have gotten names. Brack distinguishes yellow flowered phyllacanthus from purple-ish striped flowered phyllacanthus by appending "violaciflorus" to the name. Probably not easy to trace that.

I have been trying to get my hands on an unpublished PhD dissertation that attempted a biogeographic revision of the genus back in the '70s but have not found it in the usual places. The apparent main issue is that the various spine and rib forms are not distinct in the field and intergrade, making field identification by the standards of the extreme forms maintained in cultivation difficult if not impossible. Apparently Hunt and others relied on this PhD dissertation to eliminate a great many names for "extreme forms" in cultivation.

A good overview of the genus in cultivation is the article by Elton Roberts in the Sept/Oct C and S Journal. He has photos of some forms you don't see very often. I have been buying all the "names" from Brack and just seeing what they look like in a pot. Some seem rather distinct and others not so much. It's a very interesting bunch though and highly entertaining, even if not taxonomically clear.

peterb

[iann]

I have the Mesa Garden SB437 "Grandicornis" which is listed under Echinofossulatus phyllacanthus, but I think is really S. crispatus:

grandicornis-160411.jpg (82.7 KiB) Viewed 1624 times

[DaveW]

You may be able to get a copy of that unpublished dissertation Peter if you write or email the university concerned? Roy Mottram (Whitestone Nurseries UK) seemed to get some of his stuff this way.

[DaveW]

Depending on how good your language skills are Barry, or if you can use an online translator:-

http://www.cactuspro.com/encyclo/Stenocactus" onclick="window.open(this.href);return false;

[BarryRice]

Ooh, a key!!!!!! Thanks Dave. I can run some of the vocubulary past some friends, too. Thanks!!!

[peterb]

"Backeberg recognized 32 species, Bravo 21 and David Hunt 8." haha. Good luck with that.

peterb