Moon Cactus Stem Rot: #1 Cause and How To Remedy

It’s disheartening to see a Moon Cactus stem rot, as it can be distressing to witness a beloved plant facing such a challenge.

moon cactus stem rot
Thriving Moon Cactus

If you notice the issue, it’s important to address it promptly (and gently as well) to give the cactus the best chance for recovery.

While Moon Cactus stem rot can be disheartening, don’t lose hope just yet!

In this post, we’ll explore the reasons behind their limited lifespan and address potential solutions to save them from this concerning condition.

Yes, there is a way to rejuvenate these captivating plants and nurse them back to health.

Moon Cactus Stem Rot: Why It Is So Common

Moon cactus, the eye-catching colorful fusion of Gymnocalycium and Hylocereus, can be a delightful addition to any collection.

Given that these cacti are typically grafted, the vulnerable joint between the colorful upper cactus and the rootstock becomes particularly susceptible to excess water. 

Overwatering, poorly draining soil, or high humidity levels contribute to the moisture accumulation that leads to rot.

moon cactus stem rot
Colorful Moon Cactus

Signs of Moon Cactus Stem Rot

Symptoms of stem rot in moon cactus include black or brown discoloration near the base of the cactus, accompanied by soft, mushy tissue.

As the rot progresses, the affected area may become discolored, and the plant might begin to show signs of wilting and a decline in overall health.

Overwatering Signs

To determine if your moon cactus has been overwatered, look for the following signs:

  • The rootstock is turning brown or becoming mushy.
  • The soil is wet and soggy, but you haven’t watered the cactus in the last 24 hours.
  • The roots of the cactus are brown or black and mushy.
  • The cactus is not planted in well-draining soil.
  • You have been watering the cactus without allowing the soil to completely dry out first.
moon cactus stem rot
Colored Albino Cactus


  1. Fix The Damage

To address moon cactus stem rot, start by assessing the affected plant. If the rot hasn’t extensively spread, swift action can save the cactus. 

  • Carefully remove the affected part of the cactus using a disinfected blade, cutting until the healthy tissue is reached. 
  • Afterward, allow the area to dry and callous for a few days before replanting the cactus in fresh, well-draining soil. 
  • Ensure the pot has proper drainage to prevent excess water accumulation.
  1. Adjust Watering Routine

Prevention is key in managing this issue. Adjust the watering routine, allowing the soil to dry out between waterings to prevent further complications. 

  1. Repot If Necessary

Consider replanting the cactus if the roots are still white and healthy. Give it a well-draining soil mix – primarily consisting of cactus or succulent potting mix – and allowing the soil to dry out completely before watering again

  1. Find New Area

Lastly, ensure the plant is situated in an area with good airflow and adequate sunlight, but avoid exposing it to direct intense sun, especially if it’s already stressed from the rot.

moon cactus stem rot

Important Note: If your cactus isn’t receiving enough light to utilize the water you provide, it needs more light.

These cacti love abundant light and thrive near west-facing, east-facing, and south-facing windows.

Placing them more than a foot away from a window may deprive them of sufficient light, resulting in issues.

Personally, I keep mine right on the windowsill of a west-facing window to ensure they receive ample light.

Save the Rootstock If You Can

The rootstock, the green stalk supporting the colorful cactus on top, can regain its ability to sustain itself if you remove the scion or the colorful, spiny top cactus.

Once the scion is removed, the rootstock will callous over and begin to support itself.

Eventually, it will even produce new growth, which it was previously unable to do. Follow these steps to grow your own cactus using just the rootstock:

moon cactus stem rot
  1. Get a sharp, clean knife.
  2. Make a clean cut through the Hylocereus undatus cactus, below the scion.
  3. Remove the scion entirely, along with any excess rootstock.
  4. Place the rootstock in a sunny window and allow it to callous over.
  5. Water the cactus only when the soil is dry and be patient.

Note: This method assumes that the rootstock is still healthy, green, and firm.

Understanding the Moon Cactus’ Fate

The moon cactus’ destiny is predetermined due to the parasitic relationship between the scion and the rootstock.

The rootstock is unable to produce sufficient food to sustain both itself and the scion indefinitely.

Over time, the rootstock weakens from lack of nourishment, ultimately resulting in the demise of both cacti.

moon cactus stem rot

Moon cacti are a bit mysterious in terms of their lifespan since it’s like they’re carrying a secret from their time before you meet them.

Normally, they strut their stuff for about 1.5 to 3 years before they start acting a bit under the weather.

Yet, if they’re drowning in water or lacking that bright sunshine, they might lose their sparkle a tad faster.

My Personal Experience Saving a Moon Cactus

I cared for my moon cactus with great affection for about 2 years until I noticed it starting to decline.

That’s when I discovered that I could save the rootstock by removing the scion.

On August 11, 2019, I removed the scion, and my precious dragonfruit rootstock showed signs of renewal.

For a month, there seemed to be no change, but in mid-September, when I went to water it, I witnessed new growth!

A little green nub on the right side of the cactus emerged, indicating that my dragonfruit was happy and thriving.

moon cactus stem rot

If you wish to save the scion, you can remove it and graft it onto a new rootstock. However, I chose not to do this as I believe the scion’s survival in nature is unlikely.

Instead, I let it naturally wither after removal, giving it its own pot. Ultimately, the decision to graft the scion onto a new cactus, as the rootstock weakens, is yours to make.

Note: The scion should be healthy, vibrant, and free from browning or mushiness for this method.

An Alternative Option: The Chin Cactus

If you’re looking for a cactus that can thrive independently, consider the chin cactus.

These stunning plants, similar in appearance to the colorful balls of moon cacti, are often found in various hues, including variegated versions with neon pinks, reds, and yellows.

Unlike the scion of moon cacti, these chin cacti possess chlorophyll, enabling them to support themselves. No rootstock is needed.

moon cactus stem rot

Final Thoughts

By understanding the unique nature of moon cacti and implementing the right care, you can extend the lifespan of these enchanting plants.

So, if you find yourself captivated by their vibrant colors, don’t hesitate to bring them into your home.

Just remember to provide them with the care they need and revel in the beauty they bring.