What is a moon cactus?

by Lynn KirkOct 23, 2021

moon cactus


A mutant! Seriously, the moon cactus is one of the coolest mutants in the plant galaxy. Its stellar appearance is one that causes you to stop and gaze … or perhaps buy and collect.

But besides being a mutant, exactly what is a moon cactus? Well it is not a type of cactus that grows on the moon. Better yet, it’s two cacti for the price of one! The following rundown explains . . .

Strange beginnings?

Botanically speaking, the moon cactus is a Gymnocalycium Mihanovichii. That’s the end product when a shoot or bud from a Chin cactus is successfully grafted onto a night-blooming cactus.  

  • The Chin cactus (scion or donor plant) is found in the desert climates of South America, such as Paraguay and Argentina. The first European to write about them was the “Cactus Man,” a.k.a. Alberto Vojtěch Frič, in the early 1900s. This succulent produces clones (offsets) that can be easily cut and grafted to another plant base.
  • The night-blooming cactus (rootstock or bottom plant) is a tropical cactus, with aerial roots, that climbs or sprawls. 

After grafting the chin cactus onto the night-blooming cactus, the plant tissues of the two species (and sometimes other rootstock species) slowly join together over a month or two. Once healed, they continue to grow as one cultivated plant a.k.a., an out-of-this-world mutant called moon cactus!

Nude or not?

Most moon cacti have a seemingly celestial characteristic: They're colorless! The reason is simple. The moon cactus has no chlorophyll in its plant cells. Without chlorophyll, its colorless “body” enables us to see the plant’s underlying colors. And what neon colors they present: sunlit orange, lemony yellow, and firecracker red. Other mutants appear as muted pink and luminous white or variegated versions that create rainbows of color.

Meal service?

The base or rootstock cactus is green because it produces chlorophyll. That’s good news for the moon cactus because chlorophyll is necessary for photosynthesis to occur. Through the photosynthesis process of the base cactus, nutrients and energy are transported to the moon cactus above. Consider it shared energy for sustenance and growth.


A moon cactus is usually unmistakable. For most, the upper plant-form resembles the size and shape of a full moon that rises proudly from atop its host plant. As it matures to around 2 inches diameter, it forms branching offsets.

Quills or spikes?

The moon cactus involves two plants, so no surprise that it presents two thorn types. The “head thorns" are those that grow on the top cactus. They’re typically short and somewhat soft like fine quills.

Conversely, the base or "rootstock thorns" can prick and poke. They’re also short but tend to be sturdier and spikier.

Spring flowers without showers?

The moon cactus has phases, just like the moon itself. In spring, its dormant season comes to a close and flowers can appear. The blooms are as unusual as the plant. Silky and funnel shaped, they tend to grow from the sides of the cactus.

Groom and resume?

The moon cactus offsets can morph the globular shape, so some maintenance may be required if you prefer the all-round look. Just pluck off the cloned branching and graft it onto a host plant before the cuts dry.

Round two?

The life expectancy of the moon cactus is a year or two. That’s because the top and bottom plants grow at different speeds, which eventually breaks the graft. However, gardeners can then re-graft the scions or clones onto another rootstock for a second round of galactic splendor!

Moon needs sun?

Yes, indeed! Just like most other succulents, the moon cactus thrives best in indirect light that’s bright, but not so hot that it fries the plant. Most grow indoors, such as on a sunlit windowsill at home or office. If the cactus’s color starts to fade, it might need more light.

Toil with the soil?

A moon cactus prefers specially prepared potting medium with decent drainage. Some gardeners make their own mix by adding pearlite or pumice, but that’s just extra work! Pre-packaged cactus and succulent soil blends are a lot easier, reasonably priced, and less risky. Miniature rocks layered in the base of the pot also help ensure adequate drainage, as does a pot with drainage holes.


The moon cactus lives up to its cactus name. It stores water for when needed, so seldom does it need more. However, that doesn't equate to total neglect. The plant medium should feel almost totally dry before adding more water. Sometimes that means a little more water in summer and a little less in winter. As with other succulents, "wet feet” can be deadly.

A moon cactus makes an out-of-this-world gift. After all, mutants are super cool to have around . . . especially during Hallow-Moon!