What is a Moon Cactus?

A moon cactus is a succulent that is native to desert climates. Its Latin name is Gymnocalycium mihanovichii, and it has several common names such as ruby ball cactus or Hibotan. The moon cactus itself is a mutant that lacks the chlorophyll necessary for a plant to feed itself via the process of photosynthesis, or converting sunlight to energy. This species is, therefore, typically grafted on top of another type of cactus from which it feeds. The resulting bright color of the Hibotan makes the plant popular as decoration, though it has a relatively short life for a cactus.

Without enough chlorophyll to turn sunlight into food, a plant will die; this is the case with moon cactus seedlings. They can survive for only up to a few weeks on their own. If a Gymnocalycium mihanovichii is grafted onto a chlorophyll-dense succulent, however, it can live for many years.

Most plant nurseries will sell moon cacti that are already grafted and flourishing. If a gardener wishes to do the grafting at home instead, many books and websites include instructions on how to do so successfully. The main idea is to cut the top of the base cactus and the bottom of the moon cactus off. Then, by lining up the insides of both cacti, the two plants will heal by becoming one plant.

The Hibotan should begin to grow as it feeds off of the base cactus. Typically, the top plant will turn a bright shade of yellow, orange or red. This effect is caused by the revelation of the plant’s underlying pigmentation and the lack of chlorophyll, which gives plants their usual green color. It is common for people to confuse a moon cactus with a cactus flower.

Depending on the type of base cactus chosen, a moon cactus might not grow much taller than 12 inches (30.5 cm). While several kinds of cacti live for up to several decades, the Hibotan has a relatively short life span. The base cactus cannot often support the entire plant for longer than a few years.

One can help to ensure the longest lifespan possible by following a few specific care instructions. The ruby ball cactus, unlike some other cacti, does not thrive in direct sunlight. A few hours of indirect, bright sunlight each day is optimal. Many people who own this plant find that it does well in a window that gets direct sun, as the tint in the window dilutes the intensity of the light just enough.

Like many cacti, the moon cactus should not be watered too often, or it could die. One should wait until the soil it grows in has completely dried through. Then, the plant needs to be drenched with water as if to mimic receiving a lot of rain. The plant will not need any more water until the soil has completely dried through again.