Mammillaria to ID, please

Hi all!

Unfortunately, I do not recall if it had a taproot or not when I transplanted.
It is about 2 inches (5 cm) in diameter and newly out of its tiny nursery pot.
The black central spine is very distinctive, but is not so clear in the photo.

Thanks for any suggestions.


Shmuel

Hi Shmuel, and welcome to the Forum. Your plant looks very healthy and is I am sure, Mammillaria heyderi.
This species has (according to Hunt) 5 subspecies, and of these your plant is either ssp. heyderi or ssp hemisphaerica. The only real difference is that ssp. hemisphaerica has few radial spines than ssp. heyderi (9 to 13 vs 15 to 22), and is generally a flatter plant. Now, I count about 15-16 radial spines on your plant, so I'd choose Mammillaria heyderi ssp heyderi as you plant.
Best wishes...

Hallo Shmuel!
Yes, M. heyderi form
Best wishes from Slovenia Andrej

Wow, thank you for such a quick reply, Chris and Andrjpr. Mammillaria heyderi ssp heyderi it will be then. I saw the ssp list on your Names list. Very fascinating, but hard to say what to do with them. Is that list the one by Hunt you mentioned? I'm an old-timer and used to use Hortus III for ID! Times have changed.

Now I see it is cold-hardy and I assume it should be kept pretty dry for the winter.

Thanks again for your quick reply.

Yes, Shmuel, it will withstand dry cold OK. I'm not sure exactly your climate, but in UK, I keep my plants dry from early October until early March, temperature minimum 7C in my greenhouse.
Classifications are always changing, I'm afraid, and they depend very much on the attitude of the botanist creating the list as to how significant differences are, and whether the common characters overcome any differences. It is a judgement thing, and has raised a lot of heated debate. Most of this is, I believe a total waste of time.

My approach is that I choose one classification around which I organise my collection. But I do recognise that a plant named as X may also be called Y in someone else's classification.

An example of this could be Mammillaria magnimamma. One classification (Hunt) has this as a single very variable species. Another (Reppenhagen) uses the name magnimamma for a specific form, and uses other names, such as bucareliensis, vallensis, .... for other forms of what Hunt would simply call M. magnimamma.

I'm no botanist, so really cant tell who is right or wrong, if anyone is, so I label my plant as Mammillaria magnimamma 'bucareliensis', ideally with some field number to denote who found it and where it came from. I think that's called covering all bases!

Classifications can be found usually in pdf form on the AfM website and on the UK Mammillaria Society website.