Grafted Cacti Explained

Humans have for long liked to tinker with plants. In the past most of it was down to creating better, higher yielding food providing plants. Nowadays, we still graft and genetically modify edible plants, so they are more resilient, tastier and superior, but we also play more with ornamental plants.

Grafted cacti are a result of this human intervention, but there is more to grafted cacti than meets the eye. Below we will try and answer all the questions about these intriguing plants.

What is a grafted cactus?

Simply put, grafted cactus is a plant made of two or more different species of cactus growing together as one. The cacti have to be compatible as not all species of cactus are suitable to be grafted. In horticultural terms the top part is called the scion and bottom, the rootstock.

To create a grafted cactus, both cacti need to be cut. The bottom of the plant, or the rootstock is cut on the top while the top, the scion, has a bit of its bottom sliced off. They are then joined and if the procedure is done correctly, their wounds will heal in such a manner that they will be joined, grow together and share the same nutrients.

When talking about grafted cacti most people think of the green and red, yellow, orange, pink, purple plants or Moon Cactus. These are the most common form of grafted cacti and can be easily purchased in garden centers or succulent nurseries.

The colourful top is often mistaken for a flower due to their brilliant and vivid colours but, in fact, the scion of the Moon Cactus comes from a plant called Gymnocalycium Mihanovicchi. Not only that, all of the Moon Cactus scions, except for purple, are also albino forms.

This means the plants lack chlorophyll and therefore cannot preform photosynthesis. They would die on their own and can only survive if grafted onto rootstock that can do photosynthesis for them.

What are the origins of the Moon Cactus/Ruby Ball Cactus?

The Moon Cactus, or the colourful top was born in Japan during the 1940’s where 2 growers (E Watanabi and K Kitoh) raised Gymnocalycium Mihanovicchi seeds. Some of these seeds have naturally mutated and grew a bit more red than the others. By selectively breeding (picking the best and most colourful offsets these cacti produced) and grafting, over time the bright colours we enjoy today were achieved.

Naturally, these fantastic plants have spread all over the world and with the help of tissue culture technology their production has accelerated. Not only could the exact replicas be achieved in great numbers, tissue culture also sped up the growth.

How do you care for a grafted cactus/moon cactus?

Grafted cactus is not always necessarily a moon cactus. Other compactible varieties of cacti can be grafted together. The original plants will determine the best way to care for such plants. In general it is best to have grafted cacti growing in succulent potting mix, in extremely bright shade/filtered light and water sparingly depending on the seasons.

Moon Cacti (the colourful, albino, chlorophyll-lacking Gymnocalycium Mihanovicchi) need a little extra TLC than other grafts as albino plants are quite sensitive to the elements, especially direct sun.

Without chlorophyll, the moon cactus, even when grafted, can easily get burned by the sun’s UV rays if exposed on warm days. The best spot for Moon Cacti would be in a very bright spot indoors, on a shaded veranda, under a tree or in a greenhouse.

I found that as long as Moon Cacti are planted in very well-draining succulent potting mix, they won’t suffer if accidentally watered too often especially when they live outdoors.

Indoors, keep Moon Cactus on the dry side and water only once the potting mix has completely dried out. The pot should also have a drainage hole.

Moon Cacti grafts are not frost tolerant and should be shielded from temperatures below 1C/33F.

Other grafted cacti that do not have an albino/ variegated rootstock or scion are quite a bit more hardy and can cope with stronger sun. Cacti usually do not like to be watered too much so avoid overwatering and make sure the potting mix is allowed to dry out completely between waterings.

How often do you water a grafted/moon cactus?

A good rule to watering cacti is to allow the potting mix to dry out between waterings. If the plants are indoors leave them on the dry side for a couple of weeks before drenching them well.

In winter only water if the cactus is shrivelling. There is no magic number as the frequency will depend on how dry your house is, where the plant is kept and how good the potting mix is. Never keep your Grafted Cactus sitting in waterlogged potting mix.

How much light does a grafted/moon cactus need?

Moon Cactus does not like to be in direct sun for too long (early morning sun/ sun in winter is ok), but still needs a very bright spot. A light filled spot by the window, shaded outdoor area, filtered light or a greenhouse with a 30% shadefactor will all be a good home for most Cacti.

Grafted Cacti that are not albino/variegated might need a little more sun, depending on the species used for the grafting.

How long does a grafted/moon cactus live for?

Moon Cactus and other grafted cacti can have a shorter life span than cacti growing naturally as sometimes the rootstock can grow faster than the scion (or vice versa). The moon cactus can live for over 5 years depending on the conditions it is kept at.

Better its environment, longer it will live. Other grafted cacti should have a longer life, especially if the two species are particularly compatible.

At the nursery we grow grafted cacti, including the moon cactus and although we don’t see them age as they get sold, I do have a couple in my private collection that are over 5 years old. They live in a greenhouse and get re-potted once a year into fresh succulent potting mix.

The reasons for grafted cactus top dying

The main reason grafted cacti/ moon cacti die is lack of light. They can also die when overwatered, underwatered or when exposed to strong direct sunlight. Humidity and heat can also spell trouble for a grafted cactus. Although not very common, snails and slugs can kill the top part by eating into the centre.

Grafted cacti are marketed as indoor plants and they are very good indoor plants as long as they have enough light. The problem is that many people put them away from windows, in dark rooms or they shut the blinds when going to work. All of this limits light exposure and eventually the plant will collapse.

Can I grow top of the Grafted Cactus/Moon Cactus on its own?

In the case of the Moon Cactus the simple answer is no. Albino plants will not survive on their own and while they will live for a little while, they eventually die. Other grafted cacti that are not albino will survive on their own.

Many grafts will produce offsets and while they will need to be kept on on the Moon Cactus (or be grafted onto rootstock), others can be propagated further by snapping the offsets and planting them.

In conclusion Grafted Cacti are a fun and interesting pant to add to the collection and with just a little bit of extra TLC will beautify your home for many years.

If you’re in Australia and are after some grafted cacti ou