Hylocereus from graft

We all know of those colourful Gymnocalycium grafted on Hylocereus but does anyone know what species the stock plant is?

I bought one and immediately cut off the top in the hope of getting a real species of Hylocereus, not some cultivar from a commercial fruit. Now It's more than twice the size.

It is hylocereus undatus I think. Probably it is the dragon fruit as the commercial fruit varieties have been selected for vigour.
I haven't had much luck grafting on this stock, it is thin at the centre near the vascular bundle so probably works best with seedlings.
I have seen Hellonasty do some great things with hylo.

Originally I thought so too but the stem undulations are not characteristic of that species in my opinion. H. undatus looks more strongly undulate than this stock and in this plant the undulations look less symmetrical.

I may be wrong (there's not much to work with), it could be due to some difference between juvenile and adult growth.

I have heard of it being on other stocks, H. trigonus, H. triangularis and H. ocamponis. The first is too thin, and so would not be the one, but the others look promising.

Of all the species listed in The Cactaceae, I have narrowed it down to some species with reasons why it is not the others. All I used were the descriptions, figures, my own plant and my knowledge of the appearances of other plants in shop displays.

Based only on the thickness of the stems it could be:
H. guatemalensis
H. purpusii
H. ocamponis
H. bronxensis
H. polyrhizus
H. venezuelensis
H. costaricensis
H. undatus
H. cubensis
H. monacanthus
H. stenopterus
H. napoleonis
H. triangularis
H. antiguensis
H. calcaratus

These are too thin:
H. lemairei
H. extensus
H. trigonus

Of those of acceptable thickness, the stem margins are examined.
It could be:
H. guatemalensis
H. purpusii
H. ocamponis
H. bronxensis
H. polyrhizus
H. venezuelensis
H. undatus
H. monacanthus
H. stenopterus
H. napoleonis
H. triangularis
H. antiguensis

Stem margins are completely wrong:
H. costaricensis
H. cubensis
H. calcaratus

So it could be any one of the following:
H. guatemalensis
H. purpusii
H. ocamponis
H. bronxensis
H. polyrhizus
H. venezuelensis
H. undatus
H. monacanthus
H. stenopterus
H. napoleonis
H. triangularis
H. antiguensis

I did not discount any species that have characteristics unlike this plant, but not too dissimilar for this difference to possibly be caused by differences in juvenile and adult growth.
Therefore this long list of possible plants could be much shortened when the plant grows some more. When it flowers, floral characteristics and perhaps even fruit could be used to identify it.

So I am calling for anyone who has grown this plant to maturity form one of these grafts to help me identify it. My one will not be much use anymore until next growing season, and with all this rain it has started to rot at the bottom. I cut it and it is drying now. It will take a long time before it flowers.

Anyone know anything? Maybe a more up-to-date source?
This is really eating at me.

Hi Cereoid,

To my knowledge H.trigonus, H.triangularis and H.undatus are very good stocks.
The commercial grafting stock for gymno´s or chamae´s is H.trigonus.
They get "fettened up" by removing the areoles and the tip of the cutting before it gets rooted.
(Thats why you mostly won´t get no pups of these stocks)
Without the ability to grow they become nearly cylindrical and it´s easy to graft on.
H.trigonus is cold tender and so is H.triangularis. As a stock they survive only a year or two in European Collections .
The tougher one seems to be H.undatus. Sadly its vascular bundles become
woody very quickly and more care has to be taken to make the graft successful.

Cheers Snah

That's interesting about their preparation. I never thought of them being thickened like that, but I am not sure just how much thicker doing that could make them get.

Could that increase the thickness of the stem enough to make a naturally slender vine look like a naturally thick one? If so then H. trigonus could be the species we see in shops.

It might even be a combination of different stocks from different suppliers and that could explain some of my confusion.

I have noticed that the areoles are in tact, at least in the one I bought because it grew from one of them.

Has anyone grown one of them to maturity from one of those Gymnocalycium grafts?

I looked in the scientific literature and found invariably (from the papers I looked at) that the stock plant is referred to as Hylocereus trigonus. I searched for the scion plants and stock plant by name and did not find any reference to another stock being used. Some even had pictures that show the plant as looking the same as the ones we see here.
I am satisfied that I know what it is.

On a side note mine has started growing again.