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Moon Cactus Care: Tips for Growing Vibrant Cactus Plants

Moon Cactus Plant

A rainbow of moon cacti! Hibotan tops in shades of red, yellow, pink, and orange make this collection a colorful delight.

Photo Credit
lovelypeace
Botanical Name
Gymnocalycium mihanovichii
Plant Type
Cacti/Succulents
Sun Exposure
Part Sun
Soil pH
Acidic
Neutral
Bloom Time
Spring
Summer
Flower Color
Yellow
Pink
Hardiness Zone
11

Essential Care Guide for Moon Cactus: Light, Water, Soil, and Propagation

Written By: Lauren Landers Master Gardener and Contributing Writer

If you love houseplants with big, bold color, you’ll be over the Moon for moon cactuses. These colorful characters are the product of a bit of playful plant experimentation, and while they don’t exist naturally, they may just become your new favorite indoor or outdoor addition. Here’s everything I’ve learned from years of growing and grafting them.

Caring for a moon cactus is a little different from tending their cacti cousins. The vibrant Hibotan tops of moon cactuses need a grafted base to thrive—but with the right tips on light, water, soil, and occasional grafting, you can keep your colorful plant healthy and growing. I have a soft spot for moon cactuses—they were the very first houseplants I ever grew!

About Moon Cactus Plants

Also known as the red ball or red cap cactus, moon cacti are created by grafting two separate types of cacti together to create a small hybrid plant that’s truly one-of-a-kind! The top section of moon cacti is actually a mutated version of the Hibotan cactus, which doesn’t have the chlorophyll it needs to photosynthesize. To keep it growing, this Hibotan cactus top is then grafted onto a tall cactus base, often from a dragon fruit cactus (Hylocereus spp.), which provides enough chlorophyll to keep the Hibotan cactus top healthy.

Wild Hibotan cacti grow native throughout the arid regions of South America, but they don’t have the bright colors houseplant lovers have come to expect from cultivated moon cactuses. While store-bought moon cacti come in showy shades of pink, yellow, red, orange, and purple, wild Hibotan cacti are a grayish-green color and can photosynthesize on their own. It’s only when Hibotan cacti are carefully bred for that extra special color that they lose their ability to support themselves and require grafting.

Two small, colorful moon cacti in pots
Bold, bright, and totally over the Moon. These potted moon cacti are a playful pop of color for any windowsill. Credit: Dipanjan Adhikary

Like other cacti, moon cactuses sport small spines that can prick your fingers, and they grow best in warm locations with well-draining soil. However, because of their special coloring, moon cacti don’t tolerate as much sun as your standard cactus plant and prefer to grow in bright, indirect light. I keep my moon cacti in a small pot in a partially shaded window, where they seem quite happy. However, these plants can also be grown in dish gardens with other cacti and succulents that have similar care needs. Additionally, they can potentially be grown outdoors in light shade in Zones 11 and 12.

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Planting

As with other houseplants, I like to repot moon cacti as soon as I bring them home as I find the store-bought pots they arrive in can increase the risk of root rot. I’ll often grow these plants in well-draining terra-cotta pots that wick moisture away from their delicate roots, but you can also grow them in shallow-dish garden containers with drainage holes in the base.

  • Choose a small pot: Moon cacti don’t mind being a little crowded in their pots and oversized pots can increase the risk of root rot. That’s why I grow these plants in small terra-cotta containers that are about the same size as the store-bought pots my cacti arrive in.
  • Use cactus soil: Using a well-draining potting mix is key for growing cactuses, including moon cacti. You can either use a store-bought cactus and succulent potting mix or make your own mix by blending together 3 parts potting soil, 3 parts sand, and 1 part perlite or pumice.
  • Wait to water: After repotting, wait 1 week to water your moon cactus to give its roots a bit of time to settle in.

Growing

Compared to other cacti, moon cacti are a bit harder to grow, and they usually live for only a few years, even with the best of care. The complexities are that the top and bottom sections of moon cactus plants grow at different rates and the graft union that forms between the Hibotan cactus top and dragon fruit base weakens as the plants outpace each other’s growth. That said, you can keep moon cacti around indefinitely by regrafting the plant tops onto new cactus bases every few years or by propagating your plants via offsets!

Water
Like other cacti, moon cacti don’t need much water and can quickly develop root rot if they’re watered too much or grown in poorly draining pots. To avoid this, water these plants deeply only when their soil is completely dry, and make sure to dump any excess water out of the plant pot saucers when you're done. During winter, moon cacti may not need any water at all beyond a light misting!
Light
Most cacti grow best in bright sun, but moon cacti favor bright, indirect light. South-facing windows shielded with sheer curtains or partially opened blinds can be the perfect spot for these plants.
Humidity
Low humidity locations are best for moon cacti, but these plants should do just fine at standard indoor humidity levels.
Temperature
If you move houseplants outdoors during the summer, make sure to bring moon cacti back inside before temperatures dip below 50°F. Moon cactus bases are more cold hardy than the Hibotan cacti tops, and cold temperatures can cause the colorful moon cactus tops to die.

Fertilizer

Although moon cacti often don’t need fertilizer, they'll grow better if you feed them lightly with a cactus fertilizer during spring and summer.
Toxicity
As with most cacti, moon cactuses are nontoxic to pets—but their spines can prickle!

Types

Moon cacti are all about color, and the “varieties” come mostly from the vibrant Hibotan tops grafted onto a standard cactus base. Each color is a little personality all its own!

  • Red Moon Cactus – The classic and most common, with a bright, bold red top that instantly catches the eye.
  • Yellow Moon Cactus – Cheerful and sunny, this yellow Hibotan top brings warmth to any windowsill or dish garden.
  • Pink Moon Cactus – From soft blush to bright pink, these moon cacti add a playful pop of color.
  • Orange Moon Cactus – Warm, energetic orange tops that make a striking contrast against green cactus bases.
  • Purple Moon Cactus – Deep purple or magenta tops, less common but dramatic and elegant.

Some growers also offer variegated or multicolored tops, like red-orange blends, for a truly one-of-a-kind moon cactus. No matter the color, each moon cactus is a cheerful, low-maintenance splash of living art for your indoor or outdoor garden.

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Pests/Diseases

The most common issues that occur with moon cacti are usually caused by lighting or watering issues. However, even indoor moon cactus plants can sometimes attract pests as well.

  • Pests such as mealybugs and spider mites may feed on moon cacti, covering them with a sticky “honeydew” residue. Spot treating with a Q-tip dipped in rubbing alcohol or applying organic soap spray weekly should eliminate these pests.
  • Overwatering can cause the moon cactus bases to become mushy and collapse. If this occurs, you may be able to salvage your plant by grafting the top onto a new cactus base.
  • Too much light will result in moon cacti tops looking bleached out or scorched. If this occurs, move your plant into a lower light window or add a sheer curtain for some sun protection. 

Potting and Repotting

Yellow moon cactus (Gymnocalycium mihanovichii)
Sunny side up! This yellow moon cactus brings a pop of color to any indoor garden. Credit: MissMarch

How Often to Repot

Slow-growing moon cacti don’t need big pots and should only be repotted about once every 3 to 4 years.

When to Repot

Spring or summer is the best time to repot moon cacti.

How to Repot

  • Let the soil dry: It’s much easier to repot moon cacti when the soil is dry.
  • Reuse pots: Feel free to reuse your old pot as long as your moon cactus hasn’t outgrown it. These plants grow slowly and don’t need a lot of space.
  • Repot right: Wearing gloves, carefully remove your plant from its pot and brush as much of the old potting mix from your plant’s root as you can. Then, fill a new pot or your old one with a well-draining cactus or succulent potting mix, locate your cactus in the pot at the same depth the plant was previously growing, firm the soil around your plant’s roots, and wait 1 week to water. 

Propagation

Hibotan cactus can be grown from seed, but if you want a true moon cactus, you’ll need to graft those baby cacti onto a healthy rootstock. Grafting can also be used on moon cactus offsets or to salvage a damaged or aging moon cactus plant.

Moon cactus grafting concepts.
Grow your own moon cactus. Grafting and propagation are key to keeping these colorful cacti thriving. Credit: SHDStockProject
  • Seeds: To grow a Hibotan cactus from seed, fill pots with a well-draining cactus potting mix, sprinkle the cactus seeds over the substrate, cover them with a light dusting of grit, and keep the soil moist and in bright, indirect light until the cacti are large enough to repot on their own. If the cacti are green, they don’t need grafting.
  • Grafting: To graft a new moon cactus to a base or regraft an existing moon cactus top, use a sharp, sterilized knife to trim off the  base of a Hibotan cactus. Then, cut the top off a similarly sized, rooted, column-shaped cactus, such as a dragon fruit plant. Position the two cactus pieces on top of each other so that the cut sections are overlapping as much as possible. Secure the pieces in place with a rubber band wrapped over the cactus top and pot bottom, and care for the cactus as normal until the cactus halves fuse.
  • Offsets: To grow a new moon cactus from offsets, wait for your plant to produce babies or offsets and then carefully cut these offsets from the parent plant with a sharp, sterilized knife. If the offsets are colorful (rather than green), graft them onto an appropriately sized cactus base using the tips above. 

Seasonal Care

Like most other houseplants, moon cacti need less water in winter and they should only be fertilized during spring and summer. If the cactus base begins to produce side shoots, trim them off with a sharp, sterilized knife to ensure the shoots don’t draw energy away from the moon cactus top.

Wit and Wisdom

  • Wild Hibotan cacti typically grow in the shade of taller plants and grasses or beneath rocky outcrops that provide these sensitive plants with light shade.
  • The bright colors of moon cacti are the result of underlying plant pigments that only show in the absence of chlorophyll.
  • Hibotan cacti were first discovered in 1903 by the botanist Alberto Vojtěch Frič; however, moon cactus hybridization only began in the 1940’s.

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About The Author
Lauren Landers

Lauren Landers

Master Gardener and Contributing Writer

Lauren is a gardener, writer, and public speaker with over a decade of experience helping others learn about gardening, homesteading, and sustainable living.She combines years of practical gardening a...
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