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Plant Profiles / Moon cactus
Photos: Wikimedia Commons
Moon cactus
Gymnocalycium mihanovichii (grafted) · Ruby ball, Hibotan cactus
A colourful grafted cactus with a bright red, pink, orange or yellow ball sitting on a green rootstock. A cheerful splash of colour for small spaces.
Bright indirectLight
Every 2–3 weeksWater
ModerateCare level
Care at a glance
Light
Bright indirect
ShadeFull sun
Bright light with gentle morning sun; strong sun can burn the coloured top.
Water
Every 2–3 weeks
DryWet
Water when the soil is dry.
Humidity
Low
LowHigh
Dry air.
Temperature
10–32°C (50–90°F)
CoolWarm
Keep above 10°C (50°F).
Growth
Slow
SlowFast
Top grows to 5 cm.
Soil
Cactus mix
LeanRich
Free-draining.
Fertiliser
Monthly in summer
RarelyOften
Diluted cactus fertiliser.
Pet safety
Non-toxic
SafeToxic
Non-toxic.
About this plant
Moon cacti are mutant forms with no chlorophyll, so they can't survive on their own and are grafted onto a green cactus (often Hylocereus). They usually live a few years; the top can be regrafted.
Best spots
Bright windowsills, desks and shelves out of harsh afternoon sun.
Plant facts
| Botanical name | Gymnocalycium mihanovichii (grafted) |
| Family | Cactaceae |
| Origin | Paraguay (species) |
| Plant type | Grafted cactus |
| Mature size | 10–20 cm with rootstock |
| Growth rate | Slow |
| Spines | Short, curved |
| Flowers | Pink, on top |
| Toxicity | Non-toxic |
| Propagation | Grafting |
Seasonal care calendar
J
F
M
A
M
J
J
A
S
O
N
D
Active growth
Flowering
Keep dry
Active growthFloweringKeep dry
Based on Southern Hemisphere seasons.
Troubleshooting
| Top shrivels or browns | The graft has failed or the top is sunburnt. |
| Rootstock rotting | Overwatering. |
| Fading colour | Not enough light. |
| Rootstock pups | Remove them so energy goes to the top. |
| Mealybugs | Treat with alcohol. |
Common questions
Why is it grafted?
The coloured top has no chlorophyll and needs the green rootstock.
How long does it live?
Usually a few years.
Can I regraft it?
Yes, onto a fresh rootstock.
Does it flower?
Sometimes, with small pink flowers.
