Gymnocalycium stenopleurum.

It looks as if the top has lost its chlorophyll. I have heard/read about similar plants, but I don't think I have seen one. Was it completely green when you got it?

Thank you so much for your reply. I do not remember if the cactus was already decoloring in the center, but I found a pic where it shows very pale in the center and is turning to orange and now dark bourgundy. I just repoted it to check if it was something in his roots, it looks just fine maybe it needed some water. Keep you posted.

Paloma from Argentina

No, this has not to do with the roots, it is most likely a variegated plant, i.e. it is it a mutation with areas with no or little chlorophyll. They are much appreciated in southeast Asia, and that is where I have found most sites with pictures of these "freaks".

oops, so sorry I meant to reply to this post and posted a new one, it will not happen again.

I've been reading about hibutan and that kind of freaky gymno are used for that procedure. Now I wonder when my freaky gymno is going to bloom ;-)
TIA
paloma
the pic shows how greenish was the center spot when I bought it

So your cactus is grafted? Then it was probably done by someone who knew that the plant would become variegated, it is uncommon to graft normal, green Gymnocalycium.

I am not sure of exactly what 'Hibotan' is, I think it is a completely red clone.

They normally flower in summer, usually pink or white.

This site provides the history about hibotan, very interesting.

http://www.lapshin.org/cultivar/N12/histor-e.htm

paloma