Moon cactus dying: causes and solutions

Moon cactus dying: causes and solutions

Moon cacti, with their vibrant colors and unique appearance, have become a popular choice for both novice and experienced gardeners. However, these charming succulents can sometimes face challenges that lead to their decline.

In this comprehensive guide, we’ll delve deeper into the reasons why the moon cactus dying and provide you with essential information to help you revive and care for these delightful plants.

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What is a moon cactus and why is its lifespan limited?

First, we need to better understand what kind of plant it is.

A moon cactus, scientifically known as “Gymnocalycium mihanovichii”, “chin cactus” or “hibotan cactus”, is a unique plant found in South America formed by two cacti grafted together.

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Grafting involves connecting the tissues of two plant species to encourage them to grow as one.

The top cactus, which appears as a brightly colored spherical shape, lacks chlorophyll and, consequently, the ability to perform photosynthesis, which is vital for producing its own food. Instead, it relies on the lower cactus, often a “Hylocereus undatus”, “dragon fruit” or “pitahaya”, for sustenance by invading it with its aerial roots.

The upper cactus, commonly referred to as the scion in grafting, is sometimes called a chin cactus. The lower cactus termed the rootstock, is typically a Hylocereus undatus (or a dragon fruit).

The reason moon cacti have a limited lifespan is due to the parasitic relationship between the scion and the rootstock. The scion depends entirely on the rootstock for nutrients, but the rootstock cannot generate enough sustenance for both itself and the scion over an extended period.

Consequently, the rootstock weakens over time, ultimately leading to the demise of both cacti.

The exact lifespan of cactus plants can vary, as it depends on various factors, including their age when purchased. Typically, these cacti tend to live for approximately 1.5 to 3 years before displaying signs of declining health and eventual death.

Overwatering and insufficient light can accelerate this process, so it’s important to provide appropriate care to prolong their lifespan.

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Common causes of moon cactus dying

Let’s dive into this issue.

Root rot

Overwatering is a common mistake when caring for moon cacti. Their roots get all the nutrients from the root part and thus are highly sensitive to excess moisture, which can quickly lead to rot. Symptoms of root rot include black mushy roots, discolored base, wilting, and a foul odor emanating from the soil.

Poor soil drainage

Cactus plants thrive in well-draining soil. When planted in a pot with poor drainage, they can suffer from root issues, which ultimately affect their overall health. Ensure that the pot you choose has drainage holes to prevent water from accumulating at the roots.

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Inadequate sunlight

These cacti need ample sunlight to maintain their vibrant colors and health. Ideally, they should receive at least 6 hours of indirect sunlight per day.

A lack of direct sunlight can lead to pale, stretched-out growth and a weakened plant.


Moon cacti are not immune to common succulent pests like mealybugs and aphids. These tiny invaders can damage the plant’s structure and sap its vitality. Regularly inspect your cactus for signs of pests, such as white cottony masses or tiny insects on the plant’s surface and inside the potting mix.

Helpful: How to get rid of cactus bugs

Old age

Cactus plants are typically grafted, with a colorful top (Gymnocalycium mihanovichii or a chin cactus) and a rootstock (usually Hylocereus or dragon fruit). Over time, the top portion may age and decline, leading to the perception of the entire plant dying. This natural process is irreversible for the top portion, but the rootstock can often continue to grow.

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How to save a dying cactus?

It’s important to know this.

Assess the damage

Carefully examine your moon cactus to identify the underlying issue. Look for signs of root rot, discoloration, pests, anomalies in the potting mix, or stretched-out growth. Check if the soil is completely dry or not. Identifying a problem is the first step to effectively solving it.

Repot in well-draining soil

If root rot is suspected, gently remove the cactus from its pot and inspect the plant roots. Trim any rotted sections using clean, sharp scissors or pruning shears. Allow the cut ends to dry for a day or two before replanting the cactus in well-draining cactus or succulent soil.


Cacti plants are drought-tolerant and prefer to be slightly underwatered rather than overwatered. Plant roots can have issues with draining oxygen from overwatered pots. Water your cactus sparingly, make sure the soil is completely dry before new watering, or use pots with drainage holes. Adjust your watering schedule according to the climate and growing season.


Reviving a moon cactus suffering from underwatering is a simpler task compared to rescuing an overwatered one. Here’s a step-by-step guide on how to do it:

Prepare a basin. Begin by filling a basin with tap water.

Submerge the pot. Gently immerse the bottom of the cactus pot into the water-filled basin. Allow it to soak for a duration of 30 to 45 minutes.

During this time, the soil will gradually absorb the water through the drainage hole.

Check soil moisture. Once the top layer of fresh soil becomes adequately moist, carefully remove the pot from the basin. Place the potted cactus on a saucer to facilitate the drainage of any excess water from the soil.

Drain excess water. After approximately 15 minutes, be sure to empty any excess water that accumulates on the saucer. This prevents the soil from becoming waterlogged again.

Revival process. This method of bottom soak watering should effectively revive your moon cactus within a 24-hour period. If you find that the water isn’t reaching the top of the soil, it may indicate soil contamination. In such cases, the only solution is to repot the cactus in fresh soil mix.

Inadequate sunlight

Similar to other plants, cacti plants require light for the process of photosynthesis, which is how they produce their own nourishment. Moon cacti specifically thrive under bright indirect sunlight or artificial lighting. Inadequate sunlight can cause the cactus to yellow and brown, ultimately leading to wilting and death.

To rejuvenate your cactus, expose it to indirect sunlight for a few hours each day. Within a week, you should begin to observe signs of recovery. Keep in mind that direct sunlight can also be detrimental to cacti.

Pests treating

A common cause of moon cactus wilting or demise is the presence of pest infestations. Insects such as mealybugs, spider mites, and fungus gnats are typically the culprits, as they feed on the cactus’s stem and sap, depriving it of vital nutrients.

The methods of dealing with these cactus pests are:

Against mealybugs

To address a mealybug infestation, you can use cotton soaked in alcohol to gently dab the insects. Alternatively, create a spray solution by mixing 1 teaspoon of vegetable oil, 1 teaspoon of rubbing alcohol, and 1 cup of water. Apply this solution to the plant and repeat the process after a few days.

Neem oil is another effective remedy, possessing antifeedant properties that deter insects from consuming the plant. Mix 1 teaspoon of neem oil with 1 gallon of water and use it as a spray on the plant every two weeks.

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Against spider mites

To eliminate spider mites, wash both the rootstock and the scion with running water to remove large quantities of mites. Follow this by applying insecticides every week to control and eventually eradicate the infestation. Neem oil mixed with water is also a safer alternative for managing spider mites.

Against fungus gnats

To prevent fungus gnat infestations, avoid overwatering your moon cactus. If the problem persists, consider using insecticides as a control measure.

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Consider propagation

If the top portion of your moon cactus is dying or aging, you can propagate it to create a new plant.

To preserve the scion, you can extract the chin cacti and then graft it onto a new rootstock.

To perform the grafting process, follow these steps:

Procure a suitable Hylocereus undatus plant to serve as your new rootstock, ensuring it is of the right size.

Make a clean incision into the rootstock, removing its upper section, typically leaving about 3 or 4 inches above the soil.

Next, prepare your scion by carefully removing any remaining rootstock material, leaving only the circular section and the scion’s flesh visible. Ensure no green material remains.

Trim the top of the rootstock to create a blunt point.

Align the circular areas, known as the vascular cambium, on both the scion and rootstock. Place the scion on top of the rootstock.

To secure the grafted plant onto the rootstock, you can use a rubber band until they have fused. This bonding process typically takes around 8 weeks to become firmly established.

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Moon cactuses are captivating plants that require proper care to thrive.

By understanding the common issues they face and following the recommended care guidelines, you can enjoy the beauty of these unique cacti for years to come.

With the right care, your moon cactus can continue to delight you with its vibrant colors and unique charm. Use the article to find out why your moon cactus is dying and take good care of it.

Also Recommended to Check out a Guide: How Do You Know If a Cactus is Dead

FAQs about moon cactus care

How do you save a dying moon cactus?

To save a dying moon cactus, assess the issue, repot it in well-draining soil, reduce watering, provide adequate sunlight, treat any pests, and consider propagation if the top portion is declining.

What is wrong with my moon cactus?

Several factors can contribute to a moon cactus’s decline, including root rot, poor drainage of soil, insufficient sunlight, pests, or natural aging of the top portion.

Why is my moon cactus fading?

Moon cacti may fade due to inadequate sunlight. Insufficient light can cause them to lose their vibrant colors and become stretched out as they reach for more light.

Can you cut the top off of a moon cactus?

Yes, you can cut the top off a moon cactus if it’s dying or becoming too large.

Allow the cut end to callus for a few days, then plant it in cactus soil to encourage new growth. The rootstock can often continue to grow independently.

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