It looks like it is dying. You can cut off the dying part and the green part will grow eventually. It will look a little funny, but it will grow.

someone told me before that the colorful bulb part at the top of these cactuses are "grafted" (aka glued) to the bottom part just to sell, and the top part will ALWAYS die..

But I don't know. I've never had one that survived, personally, so I stopped buying them..

No, I know that. that is why I put it in quotes. Like, air quotes. Like I didn't mean real legitimate grafting.

rina,

I was just reading through this post, and I was wondering: Is it possible to have a gymnocalycium just on its own? They are very beautiful (unless they are just colored). Also, if they don't contain chlorophyll, how do they survive?

To the OP,

Sorry, those grafted cacti are simply doomed to die sooner or later.. The growth patterns and rates simply aren't similar enough to remain like that. I rather dislike grafted cacti...

Desirai,

But they are legitimately grafted. That is why rina pointed it out.

palms

There are some ppl that succeeded with growing the colorful top, but likely not too many. One of the members here did (maybe few???), I can't remember in a hurry who and don't know how the plant is doing now.

Gymnocalycium mihanovichii is very colorful cacti that grows on it's own roots because it has lots of or some green and can photosynthesize. Pure yellow, red, pink (Hibotan) are mutants that lack any chlorophyll and live for only while without 'help' - that's where grafting comes in. Some other plants are grafted because they are slow growers.

You could have white or nearly white (very light yellow) growth on some other succulents that would also not survive on it's own.

Oh ok, so they are kind of mutated? Thanks for clearing that up.

I was at HD and they had a big display of moon cacti. In with these plants were some cacti, looked like mammillaria, grafted just like the gymnos. I wish I had taken a picture of them.

I understand why they graft the gymnos, even if it is not my cup of tea. But a cactus that will grow on it's own and is commonly available? Makes no sense to me.

Sorry to be OT.

I did't know anything about this cactus being grafted when I got it. I thought it looked cool and got it. As soon as my cactus started loosing it's colour I started reading about it and found out that these babies are basically designed not to live for very long. I've got another one which still looks fine.

If I cut off the red part, will the green part just stay like this and continue growing?

hoovb answered that question, and yes the green part will grow if healthy. It will 'look funny' since the top is cut, but it may grow some branches/arms. It could possibly get quite large - that depends on exactly what was used as a rootstock.

Will the top just "grow together"?

Not sure what you mean by grow together? Cut part will always be cut (disfigured?) - it will (is mostly already) scab over/heal, but will not be covered in same green tissue and same shape, being invisible...just like a scar. If it grows some branches, it will/may be eventually hardly noticeable.

Truuliisa, please also note that your soil mixture is wrong for your cacti as I mentioned in your other post. Sadly, I don't think the others will last very long in the current mix they are in.

Gill

I posted in here a little while ago with my moon cactus top that i had placed in a pot of soil and it was growing roots. Only the darker purple will do this.

As it has just been an experiment for me so far I simply chopped it off when the base of the cactus got rot and placed it on a pot of soil. (Yes I am aware its not the ideal soil for succulents its probably about time I changed it over) Its been sitting on that soil now for almost 6 months and has grown a healthy amount of roots.

the gymnocalycium on my moon cactus became mushy and fall off< but the root stem is still very green and soiled, will it still grow

yes, the base usually survives. it is very hardy & that's why it is used as a rootstock. It will never grow 'new' moon cacti unless one is grafted...depending on which plant was used for rootstock, you may or may not like it...what do you mean by ..."soiled"...?

They sell multi colored ones with enough green in them to live on their own. The darker ones have enough green to do this.

Mine are several years old and do much better removed from stock.

Can't do this with the light red and yellow ones.