Moon Cactus Dying? Reasons & What to Do

Moon cactus, also known as a hibotan cactus, is a popular houseplant native to desert habitats of South America. It is usually sold as a hybrid plant combining two different species of cacti grafted together.

The top section appearing as a spherical ball, is a varied mutant of Gymnocalycium mihanovichii cacti. These species lack chlorophyll which makes them expose the red, pink, orange, or yellow coloration.

Since the moon cactus cannot make its food through photosynthesis, scientists considered attaching it as a scion to another cactus to enhance their survival. They discovered Hylocereus undatus (dragon fruit) as a favorite rootstock plant for grafting moon cactus.

Unfortunately, these plants have different growth needs, and combining them makes them have a short lifespan. The moon cactus naturally dies after two or three years, depending on the kind of care provided.

You can extend the life of a moon cactus by grafting the scion on a new rootstock. There are also great chances of the old rootstock surviving after removing the scion, which is perceived as a parasite.

How to save a dying moon cactus

If you discover that your moon cactus is deteriorating after a few years, you can take the following steps to save it.

  1. Get a sterilized, sharp knife and cut the rootstock below the scion.
  2. Remove all parts of the old rootstock from the scion (the colored ball)
  3. Get a new rootstock, preferably Hylocereus undatus, approximately the same size as the scion.
  4. Make a clean cut at the top of the new rootstock and attach the scion.
  5. Secure the two pieces firmly with a rubber band and place the grafted plant in a place with bright indirect sunlight.
  6. Also, place the old rootstock (Hylocereus undatus) in a place with bright indirect sunlight, as it may survive after removing the top.
  7. Water these cacti only when the soil feels dry to the touch. Overwatering may cause root rot.

It will take about two months for all the cacti to heal and thrive. Avoid exposing your cacti to direct sunlight. Fertilize your cacti plants every month during their growing season, starting April to September. Suspend feeding during the dormant winter period.

Moon cactus dying prematurely

Without proper care, the moon cactus may die due to the following reasons:

1. Overwatering

One of the main reasons houseplants die is due to overwatering. This is when you irrigate the plant more often without allowing the soil to dry. This problem can also happen if the soil is not draining well, the planter doesn’t have drainage holes, and the plant sits in standing water.

Plant roots need oxygen to thrive. When soil becomes waterlogged, air pockets get filled with water, drowning plant roots. As more roots die, the cactus gets mushy and changes color to brown or black. Eventually, the whole plant dies.

How to save overwatered mood cactus

Cactus root rot is a very difficult condition to treat. If you discover that your moon cactus is dying from root rot, remove it from the soil, cut off the affected roots, thoroughly wash the plant and repot it in fresh soil for cactuses.

Like most succulents, moon cacti aren’t thirsty plants. They can store water in their succulent stems for a long period of time, and there won’t be any need to water them frequently.

The soil should dry completely before watering. During wintertime, no growth occurs; thus, less watering is needed.

Moon cacti also prefer well-draining soil. Ensure the pot has drainage holes at the bottom where excess water drains. After watering your moon cactus, you must ensure it’s not sitting in any standing water.

2. Underwatering

Although underwatering rarely kill cactus plants, it causes stunt growth, discoloration, and brittle roots. It may be difficult to tell if your cactus is underwatered. However, prolonged dehydration usually results in the death of the plant once the roots dry and die.

How to revive an underwatered moon cactus

Reviving an underwatered cactus is easier than fixing an overwatered one. Here is what to do.

  • Fill a basin with tap water and submerge the bottom of the pot into the tub for 30 to 45 minutes. The water will be absorbed into the soil gently through the drainage hole.
  • Remove the pot when the top soil becomes wet and place the planter on a saucer to allow excess water to drain from the soil.
  • In about 15 minutes, remove any water that collects on the saucer before it is reabsorbed back into the soil.

This bottom soak watering should be able to revive your plant within 24 hours. If bottom watering is not reaching the top, then the soil is likely contaminated. The only option is to repot the cactus in a fresh soil mix.

3. Insufficient sunlight

Like other plants, cacti need light for photosynthesis – the process through which plants make their food. Moon cacti prefer bright indirect sunlight or artificial lighting. Without sufficient sunlight, the cactus will turn yellow and brown, eventually wilt and die.

To revive your cactus, introduce it to indirect sunlight for a few hours daily. Within one week, the plant will start showing signs of recovery. Remember, direct sunlight also harms cacti plants.

Final Thought

Moon cactus is an easy-to-care-for plant that can brighten your home. Naturally, this hybrid plant has a short lifespan but may die prematurely from overwatering, underwatering and insufficient lighting. Fortunately, you can revive your dying cactus if you discover and fix the underlying problem early enough.

References: University of Arkansas Cooperative Extension: Plant of the Week: Grafted Cactus, Neon Cacti, Moon Cactus, Hibotan Cactus

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