Controversial, Colorful Moon Cactus

Controversial, Colorful Moon Cactus

Grafted Cactus Gymnocalycium & Hylocereus

Few legal plants are as controversial in the world of gardening as the popular moon cactus. What’s not to love? These charmers look like living lollipops with the straight, dark green “stick” and the boldly colored spherical top. They can live happily indoors year round. Although loved by many and grown by more, most people don’t realize these are grafted cactus, formed by two entirely different varieties — Gymnocalycium mihanovichii and Hylocereus — and made to grow into a single plant. As a result, moon cactus are short-lived — made so by their peculiar biology. You need to better understand what you’re getting with these plants to best enjoy them.

{Please note, some links in this post may be affiliate links to sites that pay me a small commission if you click on the link and make a purchase. This commission is at absolutely no cost to you. I only recommend products and companies that I have worked with and truly love! ~Kat}

What is a Moon Cactus

large group pf pink and orange moon cactus

Gymnocalycium mihanovichii is a handsome, miniature cactus native to South America that grows just 4-inches tall and 5-inches broad. They are nearly spherical, with 8-14 ribs, typically grey-green in color with burgundy accents, short, bristly spines and white tufted points. The vibrantly colored varieties all date back to a single nurseryman in Japan in 1940. Out of 10,000 grey-green Gymnocalycium seedlings, two showed some intriguing reddish coloring. His efforts to hybridize these seedlings for more brilliant coloring were wildly successful.


However, what makes these Gymnocalycium mihanovichii so colorful is the complete lack of a critical pigment — chlorophyll. Chlorophyll is the green pigment that enables photosynthesis. It enables plants to convert sunlight into energy, to feed themselves. Without green chlorophyll, the other pigment colors in the plant shine bright. But plants cannot survive without photosynthesis. So the nurseryman grafted his colorful Gymnocalycium onto the rootstock of another cactus — and the moon cactus was born.

Today, roughly 15 million grafted cactus are traded internationally — the vast majority of them moon cactus that have been developed and produced in South Korea. They represent brilliant shades of yellow, red, orange, pink, coral, peach, purple and white. Most frequently, they are formed by grafting a brightly colored Gymnocalycium mihanovichii to a piece of Hylocereus — a climbing form of cactus that can reach 30 feet tall.

What is a Grafted Cactus?

group of colorful grafted cactus

Grafting is a technique in horticulture that takes two plants and joins them, forcing them to grow into a single whole with properties of both. For instance, fruit trees are grafted to get tastier fruit produced on hardier rootstock. Grafting is widely used in most fruit trees, tomato plants, rose bushes and many more. The plant chosen for its ornamental or fruiting qualities is grown atop another plant chosen for its health, vigor and ability to thrive in specific growing conditions. The top plant is called the scion, and the bottom is called the rootstock. In the case of the grafted cactus pictured here, the scion is the colorful Gymnocalycium mihanovichii and the vigorous rootstock is from a Hylocereus. But you can graft any compatible varieties of cactus.

Many grafted plants will enjoy a long life. But this longevity depends upon how compatible the scion and the rootstock are in a range of ways. And in the case of moon cactus, the compatibility issues doom these popular plants within just a few years. Gymnocalycium maxes out at just a few inches, while the Hylocereus grows up to 30 feet. These disparate growth patterns make it difficult to get the watering right for both succulent plant parts. Even with proper watering, in time the rootstock will outgrow the scion. While there are reports of moon cactus remaining healthy for as long as five years, a couple of years is considered good, and often, the plants die in just a few months.


When half of a moon cactus fails, the only way to save the remaining half is to cut the plant apart. If the base remains healthy, cutting off the top is all you need for the rootstock to continue to grow and thrive. If it is the colorful scion of your moon cactus you want to save, you likely will have to graft it to another cactus for it to survive. Sometimes, the purple
Gymnocalycium scions do have enough chlorophyll in order to root and grow on their own. But all of the other colors from red to yellow to white will die — quickly — without being rooted onto a healthy rootstock that will handle photosynthesis for the resulting plant.

How to Graft a Moon Cactus

closeup of red grafted moon cactus

The grafting of two cactus plants is a pretty simple process. Always use sharp, sterilized instruments. Prepare the scion, by taking the top of a healthy plant. In the case of a moon cactus, slice the top of a Gymnocalycium mihanovichii off above its basal plate — where roots emerge. Prepare the rootstock by taking a 2-5-inch rooted stem from a Hylocereus, a Cereus or a Trichocereus cactus. Slice the top off the rootstock plant, and trim the edges to taper down to the size of the scion cut. In this image, you can see where the sides of the Hylocereus rootstock were cut to taper it to the size of the scion cut.

Now, place the scion on top of the rootstock with their freshly cut edges meeting. Using a rubber band or scotch tape placed over the top of the scion and around the bottom of the pot, secure the top of the graft to the bottom. Set the plant in bright, indirect light where it will be warm, and give it 2-3 weeks for the graft to take. This video is a good one for learning to graft cactus.


Isn’t it amazing that plantscan not only live through this procedure but that they even thrive? If you want to get into grafting cactus and succulents, there are many Youtube videos that will show you step-by-step. If you are interested in learning to graft any type of plant, a moon cactus is a great place to start.

Moon Cactus Care

red and yellow moon cactus planted with mixed succulents
Watering

Moon cactus care is similar to caring for most cactus. Whether planting a solitary plant in its own pot or mixing it with other succulents, always grow your moon cactus in fast-draining succulent soil. Like with any other succulent, over-watering is the quickest way to kill your plant. Water only when the soil is quite dry, and water thoroughly when you do. Stop watering and leave the soil completely dry over the cold months of winter, even if your moon cactus is indoors. Resume watering come spring. If your graft is just a few months old, give a tiny bit of water during the winter months.

Lighting

Lighting for your moon cactus can be a bit tricky. Gymnocalycium mihanovichii is native to a shady habitat, where it can be found growing under larger plants. Without any chlorophyll, those bred for bright color are more vulnerable to sunburn. While Hylocereus can handle lower light, the plant flowers and fruits best in full sun.


Moon cactus will do best in bright, indirect light, and can be happy growing indoors year round. These plants are not cold hardy below 48° F (8.88° C) and thrive in typical room temperatures. Take care not to allow it to be in direct sun from a nearby window or it can burn.

Pruning a Moon Cactus

moon-cactus-sprouting-a-side-branch needs pruning

Sometimes, the moon cactus’ vigorous rootstock will branch and grow side shoots. When this happens, you must cut back the side growth to keep the
Hylocereus from rapidly outgrowing its colorful scion. Simply take sharp, clean pruning shears and snip it back to the stem. You now have a new stem that can be rooted to grow a whole new plant or to act as rootstock for a new grafted cactus.

Moon Cactus Flowers & Offsets

closeup of red moon cactus shows offsets developing

While many people mistake the colorful scion of a moon cactus for its bloom, moon cactus do flower in time. The daisy-like flowers are large and showy, with many petals that range from shades of pale pink to vibrant red.

Often, a moon cactus will develop small, roundish bumps, the same color as the scion, but brighter. These are not flower buds, but offsets. They start as bumps that develop into small spheres. Feel free to leave them in place. Or slice them off and graft onto a new rootstock. This is how you propagate moon cactus. In the case of a purple Gymnocalycium mihanovichii, try rooting a few of the offsets to see if they can make it on their own without a graft.


What is the Moon Cactus Controversy?

shelf of colorful, mixed moon cactus at a box store

Is it hard to believe that such a cute little plant would be at the center of controversy? The moon cactus has many ardent admirers, and seemingly just as many energetic detractors. For those who love it, the plant is adorable. It is easy to grow and to care for, even indoors. Often a moon cactus is the first they ever own. I suppose it is sort of a gateway cactus! 🙂 Detractors consider it a “fake plant”, almost on a par with painted succulents or cactus with fake flowers glue on. They object to the grafting, the short life span and the hybridizing that creates so many cactus plants entirely incapable of living on their own.


I suppose I am somewhere in the middle. Moon cactus are not a personal favorite, but I can certainly appreciate their appeal. And any plant that encourages more people to grow and love succulents and cactus is aces in my book! However, their short life span worries me. It feels like people are set up to fail with this plant. But It is an easy plant to learn grafting on, with a zillion different looks. As I’ve said before — if you know what you are buying and enjoy it — I am all for it. And that was the purpose of this blog post!

Shopping for Moon Cactus

3 grafted cactus with red moon cactus

Most people will readily find an assortment of grafted moon cactus available to order at your local big box store like Home Depot, Lowe’s or Walmart. Often, the grocery store will stock them in the floral department. The stock is usually very healthy, but take a moment to check it over carefully. You’ll also find several colors and varieties available to order online from Amazon, Mountain Crest Gardens, Leaf & Clay and The Succulent Source. You will also find cuttings and rooted plants of the cactus varieties that make good root stock. Consider trying your hand at grafting!

So… where do you fit with the great moon cactus controversy? Will you be growing your own moon cactus, trying your own grafting or giving it all a miss? I would love to hear from you. Please leave me a comment and I’ll get right back to you. If you have any questions, I am happy to help — or to debate if need be!

Because life is just better with succulents!

P.S. Please subscribe to The Succulent Eclectic! I’ll send you my FREE e-course, 7 Steps to Succulent Success! Thank you!

controversial moon cactus info and care

(Visited 13,436 times, 15 visits today)

This Post Has 22 Comments

  1. Nabeel

    Hi Kat, I have two Moon Cacti, one is yellow and one is red. There is just something about them that make me happy! The other day I saw another moon cacti in the store and it was a combination of both red and yellow and it looked so cool! I was wondering how I could pollinate/hybridize both of my cacti so that I could grow another cactus that would have the combination of red and yellow. I hope I’m using the right terms! Thank you.

    1. Kat McCarthy

      Hi Nabeel,
      Thanks so much for the comment! Yes — they make you happy — that’s a perfect reason to love them! 🙂
      You are asking the right question, but I don’t think that the mixed red and yellow will come from cross-pollinating your two moon cactus. I could be wrong — this is outside my wheelhouse. But I’m pretty sure the mixed color is a genetic mutation.
      However, in case I’m wrong, the way you can try to cross-pollinate is this: When the moon cactus bloom, lightly brush the open flower with the bristles of a small, soft paintbrush. Then, do the same with the open flower of the other plant. This way, you’re essentially doing what a honey bee does! 🙂 However, if the two plants don’t bloom at the same time (and they likely won’t), top the brush into a brown paper bag. Do it several times on each open flower and store the pollen for later use with the other plant’s flowers.
      A better bet would be to snag the next mixed yellow and red moon cactus you find. When it forms offsets, you can remove them and learn to graft them yourself!
      Have fun with this! 🙂
      Thanks for reading!
      ~Kat

      1. Namrata

        Great read! I recently got a mom cactus and it already had babies.. Have tried to graft it on a rootstock.. Let see how it goes! Fingers crossed!!

        1. Kat McCarthy

          Hi Namrata,
          How cool! I hope you’ll let me know how it goes! 🙂
          Thanks!
          ~Kat

  2. Susan mundy

    HI MY name is Susan my dad bought me a moon cactus and since putting it out side it has gone a yucky Brown colour almost clear I could be wrong but I think the soil I used may have contributed to it going like this can I save my precious moon cactus from diein

    1. Kat McCarthy

      Hi Susan,
      Uh oh… As bad as the brown color is, the “almost clear” is deadly. Typically this happens when the plant is either overwatered or it died due to freezing. I’m sorry!
      Is the plant soft and mushy? If so, it has died and there is no way to save it. But if it is still firm, then you can save it! Just follow the information here about how to save an over-watered succulent.
      Fingers crossed!
      ~Kat

  3. Bahar

    Hi,I am looking to buy variegated (black/red) moon cactus.Do know a place that I can buy?

    1. Kat McCarthy

      Hi Bahar,
      I’m sorry, I don’t know a seller I can recommend that offers this.
      I’d recommend you join a free succulent/cactus forum on Facebook or other online forum. Many feature experienced, small-scale vendors with excellent quality plants.
      ~Kat

  4. Ananta

    Hi, i’m ananta. I’m from Indonesia. I have lot of moon cactus. it’s flowering and become a fruit. I’ve been grow it and it can be sprout. The sprout colour is green like usual gymno sprout. But i don’t know it can survive or not. I hope it can be survive and become a good colour cacty.

    1. Kat McCarthy

      Hi Anata,
      If it is growing from the round, colorful top, you likely have a new offset growing. That can be left in place or carefully sliced off to graft to a new rootstock.
      But it sounds like it may ve the straight, green part on the bottom that is sprouting new growth? If so, you need to cut off the new growth and root it separately. Otherwise, it will become the dominant plant.
      If you would like to email me a photo so I can see what you are seeing – I will be happy to take a look! 🙂 kat [at] The Succulent Eclectic [dot] com
      Thanks!
      ~Kat

  5. Tiffany

    Hi, I bought 2 moon cactus last May – a yellow and a red. Both are sitting in the sunroom on the window sill and get watered about 1x week. The yellow is doing great but the red top shriveled up and died. The trunk of the plant seems healthy though and now there is a new green growth shooting out of the trunk. In reading your blog, I should cut off the new growth and start a new plant. But what about the brown shriveled top of the original plant. Should I cut that off in hopes that the plant can be saved?

    1. Kat McCarthy

      Hi Tiffany,
      If the trunk of the plant is healthy, I would recommend slicing off the red top that has died. That way, the bottom plant can thrive.
      From there, whether to make a cutting of the branch depends upon your goals for the plant. If you want to try your hand at grafting this again, I would cut back the branch and root it to become a new plant. But – if you want to grow the base plant and just enjoy it for itself – leave the new growth. The plant will revert to its natural growth habit, which is pretty cool all its own! 🙂
      Thanks so much for the question!
      ~Kat

  6. Ann Wakeford

    Hi Kat
    I LOVE succulents. My daughters know by now rather to get me a succulent as a present than any other gift. I was over the moon when they came home with all different colours and shapes of the Moon Cactus I am certainly going to try and graft some more
    Ann.

    1. Kat McCarthy

      Hi Ann,
      That’s awesome! I would love to hear how the grafting goes for you! 🙂
      ~Kat

  7. Diane Putnam

    Greetings from Oregon!

    You’ve given me an idea for a little quarantine project. When I was a kid, I bought myself a moon cactus as a souvenir from somewhere, but of course I killed it quickly with over watering. A few years ago I bought a grafted coral cactus for my office. I adored it! Well, it died. I suspect I over watered that one, even though I tried extra hard not to.

    I want to order another grafted coral to keep inside, but would like some guidance on watering this time. Also, will it stand a chance in a north-facing window? I’m not hopeful on this issue. ;-(

    1. Kat McCarthy

      Hi Diane,
      Oooohhh… I love the grafted coral cactus! I’m not certain it will get enough light in your north-facing window, but there are a couple things you can do to increase the chances of success.
      The variegated varieties do not need as much light as the non-variegated. And consider putting aluminum foil or a shiny metal tray or a glossy white poster board behind your plant. It will reflect the light back to the plant and give it a big boost! 🙂
      Thanks so much for the comment!
      ~Kat

  8. Sheryl

    If I snip off the extra little growth of the yellow top , can this be propagated and what will grow?

    1. Kat McCarthy

      Hi Sheryl,
      You *can* remove the colorful top, but it cannot grow unless you graft it onto a new rootstock.
      The rootstock can be grown on without the top, if you wish.
      Enjoy!
      ~Kat

  9. Joan

    This was a very interesting blog. Thank you for the info.

    1. Kat McCarthy

      Hi Joan,
      Glad that you found it useful!
      ~Kat

  10. Kathryn M

    I’ve had 2 moon cacti for 3 years now. I neglect them for the most part. They are in a window sill with weak light for for most of the year. I have never changed their soil and just put them in wine glasses. I water them every two is weeks or so. Mine have exploded with little buds. I got them on a whim cause I thought they would keep the cat out of the window (it worked) and they looked so cheerful 🤣 I didn’t realize I’ve gone over their typical life expectancy.

    1. Kat McCarthy

      Hi Kathryn,
      That’s awesome!
      They are very cheerful – and fun to grow! And 1 thing I have learned from years of research – these plants do not read the same stuff we do! 🙂 Don’t tell it how short-lived moon cactus typically is, maybe it will go another 3 years!
      ~Kat

Leave a Reply