Moon cactus plants or the ruby ball cactus is a grafted specimen. The colourful top is Gymnocalycium mihanovichii or Hibotan cactus. These lack the necessary chlorophyll to do photosynthesis. For this reason, the plants are grafted onto a species that produces plentiful chlorophyll upon which the moon cactus can sustain itself for several years. The lower green cactus host portion can be any number of species, but is usually a Hylocereus cactus. The job of the lower cactus is aslo to display the Gymnocalycium at an advantageous height.
Common name: Moon cactus, Hibotan cactus
Scientific name: Gymnocalycium mihanovichii
Size: 10-20 cm from base to top with flowers about 5cm wide.
Toxicity: non-toxic, even when ingested
Where to keep the plant: Indoors, on the desk or in the room anywhere with good bright indirect sunlight.
As most succulents, these plants are used to getting an abundant shower all at once between dry spells. Water thoroughly once and then let the soil dry up a little before watering again.
This might come off as a surprise but these plants do not enjoy a full sun like most cactus species. It can do more harm than good. Lots of indirect sunlight is best for them.
The plant despises wet feet, thus a quick draining soil is the ideal type. There are even cactus soil mixes available in the market. An organically rich soil is perfect.
Due to the unique composition of the plants, humidity tolerance are different for both the host as well as the upper plant. However, a safe side to keep both the plants happy would be to keep them is zones where there’s low humidity in general.
These plants aren’t heavy feeders. A good soil mix does plenty however, to boost growth, it is advised to provide the plant with an organic cactus fertilizer once every month during the growth season.