Double Your Cacti Love with the Moon Cactus

The Moon Cactus is native to South America. It is a grafted specimen composed of two separate cati which are artificially attached. Only the top cactus will produce blooms. Due to its nature, this plant is only grown as a potted houseplant and does not occur naturally outdoors.

Moon Cactus

Moon Cactus Appearance

A grafted Moon Cactus consists of two separate cacti. A number of cacti varieties can be the lower “host” cactus, but the popular choice is the Hylocereus cactus. Gymnocalycium mihanovichii is used as the top portion, known as the scion.

The Moon cactus scion is often of red, orange, or yellow. Blooms appear in the summer with yellowish-green flowers. The growth rate of the host and scion differ, causing the scion to outgrow its host in time. 

Moon Cactus Light Requirements

A grafted Moon cactus requires bright, indirect light. One or two hours of direct sunlight is tolerated but not from a south-facing window. Pay attention to the cacti’s health as you need to accommodate the different light needs of the host and scion. Hours of direct sunlight will fade the scion’s bright colors but the host will not thrive in low lighting. 

Water Needs

Water your Moon cactus until the soil is well moistened but not soggy. Let the soil dry between waterings to avoid root rot.

Provide water to cacti in small pots once per week. Drain excess water collected in the pot’s drip tray to keep the roots healthy. Cease waterings in the winter and switch to misting the plant. 

Temperature and Humidity

Temperature and Humidity

Average household temperatures are adequate for the Moon cactus. The cactus does benefit from winter dormancy. Move the plant to temperatures between 50 and 60 degrees Fahrenheit (10 to 15.5 Celsius) to allow the plant to rest. Provide low humidity to reduce the risk of disease and pest infestations. Use a dehumidifier for humid climates and avoid placing the plant in bathrooms or kitchens.

Soil and Fertilizer

Provide moon cacti with a well-draining cactus soil mix. The plant thrives in soil  with a low pH level. Use a soil-testing strip, available at most garden centers, to test your soil if you are unsure of the level.

Feed the cactus with a cacti or diluted houseplant fertilizer once per month during the spring and summer. Withhold feedings in the fall and winter when the plant goes dormant, which encourages healthy blooms the following season.

Moon Cactus Propagation

Propagation of a Moon cactus occurs by grafting the two cacti into one plant. Use a column-shaped host cactus for best results. Cut the tip of the cactus off with a sharp and sterile knife to create a flat surface. Cut a scion from an old host cactus. The vascular tissue and center stem of the scion will be visible. Gently press the bottom of the scion onto the flat top of the new host, aligning the centers of the plants. Place elastic bands over the scion and down to the bottom of the pot to hold the new scion in place. Avoid moving the plant until the bond has formed and the two plants have joined as one. 

Moon Cactus Pests and Diseases

Spider mites and mealybugs are the most common pests to infest Moon cacti. Treat early infestations by removing the pests with a cotton swab soaked in rubbing alcohol. Larger infestations encompassing the entire plant require treatment with an insecticidal soap or neem oil to kill the pests. Use as directed and quarantine your plant until the pests are gone. 

As with most cati, the grafted Moon cactus is vulnerable to root rot if overwatered. Water only when the plant’s soil becomes dry and do not let roots sit in water for extended periods of time. Treat existing root rot by mixing one part 3 percent hydrogen peroxide with two parts water and pouring it into the dry soil. For advanced rot, first remove the plant from its pot and trim away any dark or mushy roots. 

The Moon cactus is unlike any other cacti species. Its symbiotic relationship between two different cacti makes it a visually stunning addition to any houseplant collection. The plant’s care needs are simple, making it a great choice for beginner growers who wish to add an exotic-looking plant to their home. 

Moon Cactus FAQ

Moon Cactus FAQ

How Tall Does a Moon Cactus Grow?

Moon cacti may reach a height of 12 inches (30m cm) tall.

How Long Does a Moon Cactus Live?

On average, a Moon cactus will live one to three years. When a healthy scion outgrows the host it can be grafted onto a new, larger host. 

Why is My Moon Cactus Dying?

The most common reason for distress is root rot from overwatering. Decrease the amount of water given and check for improvement. Incorrect sunlight may also be the cause. Move your plant to a new location if too much or too little light is suspected as the reason.

Is the Moon Cactus Toxic?

No, like most cacti, the Moon cactus is not toxic but keep plants with thorns away from children or pets to avoid injury. 

Why is the Scion of the Moon Cactus So Colorful?

The scion of a Moon cactus is a mutant cacti variety that lacks the chlorophyll to turn them green. This causes the plant to show the underlying red, orange, or yellow pigmentation. 

Cindy McKie
About Cindy McKie
Cindy McKie provides helpful, easy-to-follow care guides for plant lovers of all experience levels. She has written for several online gardening publications and has self-published her own guide to growing herbs under the pen name Sophia Darby. When not writing about plants, she can be found in her gardens or reading a good book.

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