The “flying saucer cactus” is a visually striking houseplant known for its vibrant, often non-green top grafted onto a green rootstock. Its distinctive appearance makes it a popular choice for indoor plant collections.
Understanding the Flying Saucer Cactus
The plant commonly referred to as a “flying saucer cactus” is a grafted form of Gymnocalycium mihanovichii, often colorful cultivars like ‘Hibotan’ or ‘Moon Cactus’. These vibrant top portions, called scions, appear in shades of red, yellow, orange, or purple and lack chlorophyll, meaning they cannot survive independently. They are grafted onto a compatible green rootstock, usually Hylocereus (dragon fruit cactus), which provides chlorophyll for photosynthesis and nutrient absorption. This combination creates the characteristic flattened, ribbed, and brightly colored “flying saucer” appearance atop a greener base. Native to South America, these cacti are typically sold as pre-grafted plants.
Essential Care for Your Flying Saucer Cactus
Light Requirements
Flying saucer cacti thrive in bright, indirect sunlight. Placing them near an east or west-facing window with filtered light is ideal. Direct, intense sunlight, especially during the hottest parts of the day, can scorch the chlorophyll-lacking top part of the cactus. While the rootstock needs sufficient light, the colorful scion is sensitive to excessive exposure.
Watering Practices
Water using the “soak and dry” method, allowing the soil to dry out completely between waterings. Overwatering is a common issue, quickly leading to root rot, which manifests as soft or mushy spots. Water more frequently during the active growing season (spring and summer), but sparingly or not at all in dormant winter months. Underwatering is preferable to overwatering.
Soil Preferences
A well-draining soil mix is important for flying saucer cacti to prevent water accumulation. A specialized cactus or succulent mix is suitable, and amending it with perlite, pumice, or coarse sand improves drainage. Ensure the pot has drainage holes.
Temperature and Humidity
These cacti prefer warm temperatures, ideally between 68°F and 86°F (20°C to 30°C) during the day. They can tolerate slightly cooler nighttime temperatures, mimicking their natural habitat. Flying saucer cacti are not frost-tolerant and require protection from temperatures below 50°F (10°C). As desert plants, they thrive in dry conditions; excessive humidity can even be detrimental.
Fertilization Needs
Flying saucer cacti have minimal fertilization requirements. During the growing season (spring and summer), apply a diluted, low-nitrogen cactus fertilizer every 4-6 weeks. Avoid fertilizing during dormant winter months. Over-fertilization can lead to an imbalance in growth rates between the scion and rootstock, negatively impacting the graft union.
Propagating Flying Saucer Cacti
The colorful top part of the flying saucer cactus, the scion, cannot be propagated from cuttings on its own. Propagation primarily involves grafting Gymnocalycium mihanovichii onto a compatible, chlorophyll-producing rootstock, such as Hylocereus. This process requires aligning their vascular tissues and securing them until the graft union forms. The rootstock itself can sometimes produce offsets or “pups” that can be removed and rooted to grow new rootstock plants.
Troubleshooting Common Flying Saucer Cactus Problems
A soft or mushy cactus typically signals overwatering and root rot; if soft, check roots for decay and repot into dry, well-draining soil. Fading color or lack of scion growth can indicate insufficient light or a rootstock nutrient issue. Scorched spots result from too much direct, intense sunlight. Common pests like mealybugs and spider mites can affect these cacti; treat with rubbing alcohol or insecticidal soap. The graft union can also fail over time, causing the top part to shrivel or detach, often due to incompatibility or stress.