You’ve surely seen one: a small upright green cactus with a bright red ball on the top. Many people assume that this red ball is a flower, but that’s not the case. Instead it’s an albino cactus, one without chlorophyll, more specifically Gymnocalycium mihanovicii friedrichii ‘Rubra’, also called Hibotan, grafted on a green cactus. Commercially it’s sold under names like moon cactus or ruby ball cactus.
As the top plant has no green chlorophyll, that allows the underlying pigmentation, in this case a red one, to take the spotlight, giving an entirely red plant. But an albino plant can’t survive on its own, as it is chlorophyll that allows plants to carry on photosynthesis, the conversion of solar energy into sugars, and therefore to survive. Thus the red ball cactus can only live if it is grafted onto a green cactus that can carry out photosynthesis in its place. It depends entirely on its rootstock (the green part) for its survival.
In a sense, the grafted albino is a parasite: it uses the green part’s sugars, minerals, and water for its growth, yet gives nothing in return… except, to the human eye, beauty.
The rootstock used is inevitably a queen of the night cactus (Hylocereus undatus or H. trigonus) with triangular green spineless stems. This cactus is popular with growers because its grows fast and roots easily. But the Hylocereus is normally a very large climbing cactus with long stems. When you chop it into small pieces for use as a rootstock, keeping it from growing normally, it rarely lives more than 2 years. Of course, when the rootstock dies, the red ball cactus on top also dies… unless you graft it onto another cactus with chlorophyll. (More on that below.)
If the Hylocereus is so short-lived, why don’t growers use a longer-lived cactus as a rootstock? After all, it would easy enough to do and the resulting grafted cactus could last for decades. But what profit is there in selling a long-lived plant? You make much more by offering short-lived plants that people need to replace regularly. So they go with a short-lived combo that guarantees repeat business.
When the red ball cactus was launched in Japan in 1948, it was totally unique. Albino cacti were simply unknown at the time! Since then, though, it has given, by mutation or through hybridization, many other colors: various shades of red, pink, yellow, orange, purple, and cream, plus several bicolors. All are albinos and can only survive when grafted. However, there are also gymnocalyciums that are variegated, that is, partially albino and partly chlorophyllic, and even If these are generally grown top-grafted, they can also “live on their own roots” if they are rooted in soil.
Other albino cacti have been developed as well, among which the yellow peanut cactus (Echinopsis chamaecereus lutea) is the most widely available. Any purely albino cactus can only be kept alive as a grafted plant, of course, and these are also sold grafted onto stems of Hylocereus stems.
But not all grafted cacti are albinos. Many chlorophyllic cacti are sold grafted too, either because they root poorly on their own (often the case with cristate or monstrous cacti) or simply because the grower judges they look best when elevated on a rootstock. In most garden centers you’ll find grafted cacti of all persuasions.
Caring for Grafted Cactus
When two different plants are grafted together, how do you cater to their needs? After all, if they were growing in the ground, one might prefer alkaline soil and full sun, the other more neutral soil and partial shade. Or any other combination of conditions.
When it comes to grafted cacti, the secret is to ignore the needs of the top graft and instead, give the rootstock the conditions it prefers. After all, it’s the one doing all the work.
In this case, the rootstock, Hylocereus, is not your typical desert cactus that likes full sun and baking heat and tolerates extreme drought. Treat your grafted cactus that way and you’ll soon kill it!
Hylocereus does prefer very bright light, but not necessarily full summer sun, so a place in front of a fairly sunny window will be required. And here’s one concession you need to make to the albino part: don’t put any albino cactus outdoors during the summer unless you put it in the shade: they tend to burn in full sun.
Hylocereus likes to be kept fairly moist during the summer growing season. Water your plant copiously, almost as if it were a foliage plant, as soon as the soil is slightly dry to the touch, but do let it dry out more between waterings during the winter.
Indoor temperatures suit Hylocereus just fine during the summer, but it prefers cool night temperatures during the winter, between 40 and 60˚F (5 and 15˚C), if you can manage it.
Fertilize very little, since you’ll want to slow the plant’s growth down so it will live as long as possible. Fertilizer tends to stimulate growth, hastening the plant’s demise.
And you’ll never have to transplant a cactus grafted onto a Hylocereus into a larger pot, because it will put on essentially no growth.
Saving a Grafted Cactus
You can “save” a dying red ball cactus by grafting it onto a new green rootstock (the rootstock must be a cactus, not a euphorbia!). Or you can graft one of the babies that the red ball produces quite abundantly. Essentially, to graft two cacti together, you have to cut the head off the green cactus and the base off the albino cactus, then fix them together with elastics until the graft takes. But to do so, you would have to sacrifice a green cactus.
For more details on how to do carry out a cactus graft, I suggest you check out the article 7 Steps to Grafting Cactus.
Yes, you can save a red ball cactus… but most people simply buy another one their local garden center!