A Moon Cactus is a popular and eye-catching addition to any plant collection, but Moon Cacti do require specific care to thrive. From proper watering techniques to sunlight requirements, this guide will provide you with all the information you need to keep your moon cactus healthy and vibrant.
Moon cactus, otherwise known as Gymnocalycium mihanovichii, is actually two different cacti grafted together – a colorful top cactus, grafted on to a green bottom cactus. It is also known as Ruby Ball, Red Cap, Hibotan Cacti or Red Hibotan.
The top part of the cactus – the colorful ball – is a mutant variety of the Gymnocalcycium mihanovichii cactus, native to South America. The mutant seedlings lack chlorophyll which results in their bright colors. Unfortunately, this means that the young plants cannot grow to maturity. However, because of their bright colors and attractive appearance, gardeners have developed the technique of grafting these colorful young plants on to other cacti that can provide the top plant with the nutrients it needs to survive. The lower plant can be a number of cactus varieties but is often a variety of Hylocereus cactus.
The resulting grafted cactus is known as a Moon Cactus. It is only known as a Moon Cactus when the two plants are joined together as a grafted cactus. The moon cactus gets its name from its spherical shape, which resembles a moon. The moon cactus has a bright red, orange, or yellow outer top ball. Although the moon cactus is actually two separate plant varieties, it is generally known by the name of the top ball plant only, which is Gymnocalycium mihanovichii.
In order to thrive, a Moon Cactus needs you to take care of the requirements of the two separate plants it is made up of. This can make their care a little tricky, but in general, both parts of the plant are fairly hardy and have similar needs.
Moon Cactus Water Requirements
The water requirements of the Moon Cactus vary depending on the stage of growth.
Young plants require more frequent watering than mature plants.
Like most cacti, you should only water a moon cactus when the soil is dry to the touch. Allow the top few inches of soil to dry out before watering again.
Reduce watering during the winter months, when growth slows.
Over-watering is a common cause of problems with cactus and can cause root rot. Signs of over-watering include yellowing or wilting leaves, soft stems, and fungal diseases. If you think your plant is being over-watered, allow the soil to dry out completely before watering again.
Moon cactus are native to arid regions of South America, so they are used to long periods without water.
When watering your cactus, use room temperature water as cold water can shock the plant. Apply water directly to the soil if watering from above. If using a pot with drainage holes, be sure to empty any excess water from the saucer after watering so the plant isn’t sitting in water.
Moon Cactus plants are sensitive to chemicals and minerals found in tap water. Therefore, it’s best to use distilled or filtered water when watering your plant. If you don’t have access to distilled or filtered water, you can also let tap water sit overnight before using it to water your plant. This allows chlorine and other chemicals to evaporate from the water.
Moon Cactus Sunlight & Temperature Requirements
Moon cactus needs bright light to maintain its vibrant colors and compact shape. However, too much direct sunlight can cause the plant to become sunburned.
When grown outdoors in warm climates, this cactus can tolerate full sun. But if you live in a hot climate, it’s best to grow your plant in partial shade to prevent sunburn.
When growing this cactus indoors, place it near a sunny window. If you live in a hot climate, it’s best to grow your plant in partial shade to prevent sunburn.
During the winter months, when daylight hours are shorter, this cactus plant will do fine with artificial light from a grow light or fluorescent bulb. Just make sure the plant gets at least 8 hours of light per day.
Moon cactus is native to South America and prefers warm temperatures. It will not tolerate cold weather and should be kept above 40 degrees Fahrenheit (4 degrees Celsius). It is best to keep your plant away from drafts.
If your plant is exposed to temperatures below 40 degrees Fahrenheit (4 degrees Celsius), it may suffer from shock and die.
Moon Cactus Fertilizer Requirements
Cacti do not need many nutrients to thrive and your Moon Cactus will only require fertilizer sparingly. You should only fertilizer during the growing season, which is typically from spring to fall.
During this time, you should fertilize your plant once a month using a cacti or succulent-specific fertilizer.
When applying the fertilizer, make sure you avoid getting any on the leaves or stems of the plant. Instead, apply it to the soil near the base of the plant. You can also water your cactus with the fertilizer solution to help distribute it evenly.
Over-fertilizing your cactus can lead to problems such as stunted growth, yellowing leaves, and root rot. If you see these symptoms, immediately stop fertilizing and flush the soil with water to remove excess fertilizer.
Moon Cactus Soil Requirement
When it comes to moon cactus care, soil requirements are not too demanding. Gymnocalcycium mihanovichii is native to South America and grows in sandy, well-drained soils.
Moon cacti need good drainage. Overly wet soils can cause the roots to rot. A cactus potting mix or a mixture of perlite and sand will work well.
Do Moon Cactus Flower?
Owing to their rather unique structure, Moon Cacti do not flower as easily as some other cacti.
It is the top plant that blooms and it requires ideal conditions for it to bloom – usually in Spring or Summer.
Moon Cactus Pruning
A Moon cactus should not usually require pruning.
Because of their unique structure, moon cacti don’t grow in the traditional sense and don’t require regular pruning. However, if the colorful top cactus begins to outgrow the green bottom cactus, it may be necessary to carefully trim it back to maintain the graft and prevent the top cactus from becoming too heavy and falling off.
Moon cactus is susceptible to damage if pruned incorrectly or if the top cactus is allowed to grow too large, so any pruning should be done with care and precision using sharp, clean scissors or knives.
Moon Cactus Pests And Diseases
Like all plants, moon cactus is susceptible to pests and diseases.
Moon Cactus Pests
One of the most common pests that affect Gymnocalycium mihanovichii is mealybugs. Mealybugs are small, wingless insects that feed on plant sap.
They can cause the plant to become stunted and produce fewer flowers. In severe cases, they can even kill the plant. Mealybugs can be controlled with regular applications of insecticidal soap or neem oil.
Scale insects are another common pest of Gymnocalycium mihanovichii. Scale insects are small, hard-bodied pests that attach themselves to the plant and feed on its sap.
They can cause the plant to become yellow and stunted, and in severe cases, they can kill the plant. Scale insects can be controlled with regular applications of insecticidal soap or neem oil.
Moon Cactus Diseases
One of the most common diseases that affect moon cacti is root rot. Root rot is caused by a fungus known as Phytophthora cinnamomi. It is a destructive disease that can kill the plant. Root rot can be controlled with the use of fungicides.
Another common disease that affects Gymnocalycium mihanovichii is powdery mildew. Powdery mildew is caused by a fungus known as Erysiphe cichoracearum. It is a white powdery fungus that covers the leaves and stems of the plant. Powdery mildew can be controlled with the use of fungicides.
Why A Moon Cactus Loses Its Color?
The Moon cactus has a vibrant, unusual appearance. However, these plants can sometimes lose their color and become paler if the plant is stressed.
The plant can become stressed due to:
- lack of light – make sure to give your Moon cactus at least 4 hours of bright indirect sunlight each day.
- over or under watering
- temperature is too hot or cold
- problems with the lower plant – if the lower plant is stressed due to over or underwatering, or too much or too little light, it will not be supplying sufficient nutrients to the top ball
- insufficient nutrients or over-fertilizing – fertilize sparingly with a cactus specific fertilizer, carefully following the instructions on the pack
Once you have resolved the problem, your Moon cactus should start to regain its color in no time.
Moon cactus are a low maintenance plant that can thrive with just a little bit of care. By following these simple water, sunlight, and fertilizer requirements, you will help your moon cactus stay healthy and colorful.