How long does a Moon Cactus usually live?
On average, a Moon Cactus can live anywhere between one to three years. However, there are a few anecdotes of succulent keepers who have kept specimens well over five years. On the other hand, it is not unusual for a Moon Cactus to live just a few months, especially if you do not have any experience caring for one.
The short history of the Moon Cactus
In reality, the Moon Cactus is actually two plants combined into one. Or more accurately, the Moon Cactus is a product of grafting the Gymnocalycium mihanovichii with another species, typically the Hylocereus.
The Gymnocalycium mihanovichii is a small cactus that originally comes from South America. Collectors are enamored by its small stature and spherical shape. The plant is grey-green with deep purple accents. Its body can have anywhere between eight to 14 ribs.
The Japanese commercial nurseryman named Eiji Watanabe is widely considered as the person who developed what is now known as the Moon Cactus. In 1937, Watanabe bought 300 seeds of the Gymnocalycium mihanovichii var. friedrichii. He was able to successfully germinate these seeds until most of these grew and produced their seeds. By 1940, Watanabe had 10,000 seedlings. Of these two seedlings, he found two mutants with reddish bodies which he then grafted. He continued propagating Gymnocalycium mihanovichii var. friedrichii with the hope of finding seedlings with better colors.
The remarkable coloration that Watanabe was able to develop out of his collection of Gymnocalycium mihanovichii comes at a steep price. His collection lacked chlorophyll, a pigment essential for energy production in plants. This absence of chlorophyll allowed the other colors in the cactus to come to the forefront. However, this also meant that the cactus cannot survive on its own for a long period.
To work around this issue, Watanabe grafted the cactus onto another cactus called Hylocereus. resulting in what is now known as the Moon Cactus.
What is grafting?
Grafting is a horticultural technique where two plants are combined. The purpose of this technique is to grow a single plant that possesses the good qualities of two plants. This technique has been widely used in fruiting trees and ornamental plants.
In grafting, you have the scion which is the plant that is chosen because of its fruit production or its ornamental qualities. On the other hand, you have the rootstock which supplies the scion with the qualities it needs to thrive.
In the Moon Cactus, the Gymnocalycium mihanovichii is the scion and the Hylocereus is the rootstock.
In general, grafted plants have long lifespans. But the Moon Cactus is a problematic combination of two seemingly incompatible cacti. The main problem with the Moon Cactus is that the scion and the rootstock are incompatible. Specifically, Gymnocalycium mihanovichii grows just a few inches while the Hylocereus is a tall cactus, capable of reaching a height of 30 feet. The disparity in the growth rate of the two cacti translates to difficulty in getting watering right for the Moon Cactus. Initially, this disparity may not be readily apparent. But as your Moon Cactus matures the rootstock grows faster.
But apart from the disparity in height and growth rate, another critical issue with the Moon Cactus is the different care requirements of the two plants that have been combined. Specifically, the Gymnocalycium mihanovichii prefers the shade, primarily because its lack of chlorophyll makes it susceptible to sunburn. The Hylocereus, on the other hand, prefers the full sun although it can tolerate partial shade.
Although most cacti live for several years, the Moon Cactus is fated to have a short lifespan because essentially, you have two plants, with one acting as a parasite.
Over time, the rootstock cannot produce enough food for itself and the scion. This unstable combination weakens both the scion and rootstock.
Saving your Moon Cactus
Fortunately, it is possible to prolong the lifespan of your Moon Cactus. To do that, you will need to separate the scion and the rootstock.
Grafting the scion
Before grafting the scion, you will need to get a new rootstock. Apart from the Hylocereus, you may use a Cereus or Trichocereus. Make sure that the new rootstock is more or less the same size as your scion.
Start the grafting process by making a clean cut on the top of the new rootstock.
Next, take the scion by cutting around the area near the old rootstock. Do not leave any part of the old rootstock on the scion.
Afterward, place the scion on top of the rootstock. The circle that you will find in the cross-section of both plants should be aligned.
Finally, secure both cacti by using a rubber band. Typically, it will take two months for the rootstock and the scion to make a full connection.
Saving the old rootstock
After removing the scion, the rootstock can now sustain itself. In fact, after the removal of the scion, new growth will appear on the rootstock.
Once the scion has been removed and grafted to a new rootstock, you will need to make another cut on the old rootstock, just below where the Gymnocalycium was previously positioned.
Next, allow the old rootstock to callous over by placing it in a sunny location.
A short-lived beauty
Some succulent collectors oppose the sales and collection of the Moon Cactus.
They reason out that the plant damages their hobby because the plant sets up new collectors to fail because of the problems associated with keeping Moon Cactus.
If you are planning to get one for yourself, be aware of the issues mentioned above.
Image: istockphoto.com / TatianaMironenko