I can NOT ID the cactus, but IF it is a Disco, certainly it will have to be kept warm (mid 40s) and dry. I think James has quoted that he keeps some of them in his Townhouse in AZ in the winter, and the temps get down to around 45 degrees. I'm sure he will probably answer this post, so disregard my ramblings.. :-) BTW, I am keeping my two Discos and two Melos here in our kitchen in a south facing window for the winter.. Temps should not get below 50 in here..
Bill in SC

Thanks for that input. I always hate bringing plants into the house. The light is so much better in the g/h, but what must be-must be.

Al

Looks like Discocactus araneispinus but the species name is unsure because I have heard of synonyms. But it is surely a Discocactus.

Pijaya

Many thanks, Pijaya.

You have me walking in the proper direction on this.

Al

meloman, you wrote:

..... Looks like Discocactus araneispinus but the species name is unsure because I have heard of synonyms .....

I think you are referring to the following proposed taxonomical revision of the Discocactus zehntneri complex, i.e:

Discocactus zehntneri
Discocactus albispinus
Discocactus araneispinus
Discocactus boomianus

..... to become:

Discocactus zehntneri
Discocactus zehntneri subsp. araneispina
Discocactus zehntneri subsp. albispina
Discocactus zehntneri subsp. boomianus
Discocactus zehntneri subsp. buenekeri

There is a variation of this proposal that would assign the latter four subsp. to varietal forms of Discocactus zehntneri. Note the addition of D. buenekeri to the complex.

The proposal has not gained universal acceptance in the C&S community or botanical academia -- although it eventually may. The greatest resistance seems to be the inclusion of D. buenekeri -- this species does share the complex commonality of tuberculate ribs and basal offsetting, but its white, club-shaped fruit does not fit with the dark red , much elongated and slender fruit of the other candidates.

In the meantime (and as usual), use whatever nomenclature you -- and your correspondents -- are comfortable with.

James

I will print this page and put it in the folder for my Discocactus.

I am very grateful for all who contributed.

Many, many thanks.

Al

The two seedlings I have are some form of Discocactus zehntneri, and I thought yours looked similar. I did not want to say anything until James concurred..
Bill in SC

Photos pertaining to my previous post:

Discocactus zehntneri --
{{gwi:487654}}

Discocactus araneispinus --
{{gwi:487656}}

Discocactus albispinus --
{{gwi:487658}}

Discocactus boomianus --
{{gwi:487660}}

Discocactus araneispinus fruit (typical) --
{{gwi:487663}}

Discocactus buenekeri fruit --
{{gwi:487665}}

James

It would make it much easier for me to identify cacti if they were all called Discocactus zehntneri.

James, You do have a variable mess of Discocactus there. IÂve noticed that identification of plants on GW is always based on the physical appearance of the plants - not bad when youÂre dealing with various species. However, when one is trying to ID subspecies it is almost always imperative that you know the point of collection of the specimen. If you use the words "geographical variation" instead of "subspecies" it becomes more clear. A "variety" might be found anywhere within the population of the species. To further complicate things we have the term "variable species" (often listed as form or forma but not now used in taxonomy). These are variations within a species that donÂt have a scientifically recognized designation but feed the nomenclature mill of collectors. Examples - Subspecies "plants from the southern range of this species have yellow instead of red flowers". Variety "some populations of this species have yellow instead of red flowers". Variable species "this species can have red or yellow flowers". It is easier for horticulturists to identify any form as a different species (binomial) or subspecies (trinomial). You can see that a "variable species", especially one that has several subspecies presents quite a problem for the cactus dealer since each slight variation must have a different name. Many taxonomists donÂt like the classification "variety". They prefer that this be part of the "species description". GW taxonomy buffs can surely add to this simplification of plant ID.

WS, we hear far too little from you on the Cacti Gallery Forum. I wish you had more time to spend with us.

Al

Addendum to my previous posting:

In the widely referenced SCHUMANNIA 3: Kakteen und andere Sukkulenten in Brasilien (Cacti and other Succulents in Brazil) Pierre J. Braun & Eddie Esteves Pereira use the Discocactus zehntneri subsp. (araneispinus, et al), nomenclature in their synonym listing and throughout -- they may even be the original advocates -- and add:

Discocactus zehntneri subsp. horstiorum which, considering the absence of a listing for Discocactus horstii seems to imply their inclusion of the latter species in their synonym scheme. I will write Pierre Braun regarding this.

James

Another complication in attributing Discocactus in cultivation is their propensity to occasionally hybridize via cross-pollination in the greenhouse. Some growers/enthusiasts have put this propensity to good use in producing commercial hybrids that combine desirable features of different species -- a very popular one being crossing D. horstii with D. buenekerei. Andrew Tourbechev, Miles Anderson and myself (I am sure there are many others) have undertaken such hybridization. Chance cross-pollination/hybridization also occasionally occurs in the greenhouse.

Some hybrids:

crystallophilus x horstii
{{gwi:487307}}

buenekeri x horstii
{{gwi:487302}}

horstii x buenekeri
{{gwi:487668}}

crystallophilus x alteolens
{{gwi:487670}}

James

You got it going on, Sir James!!
Bill in SC