The Ruby Ball Cactus, also known as Moon Cactus, is a captivating houseplant cherished for its distinctive and vibrant appearance. Its colorful spherical top, often seen in shades of red, orange, or yellow, creates a striking visual contrast against its green base.
What Is a Ruby Ball Cactus
The Ruby Ball Cactus, botanically known as Gymnocalycium mihanovichii, is a fascinating combination of two different cacti. The vibrant, colorful top, which lacks chlorophyll, is grafted onto a green cactus rootstock, typically a Hylocereus species. This grafting is essential for the colorful upper part’s survival, as it cannot photosynthesize on its own. The green rootstock provides necessary nutrients and water, sustaining both parts.
The Gymnocalycium mihanovichii scion, the upper part, comes in various striking colors, including yellow, red, orange, pink, and white. These vibrant hues are due to mutations that expose underlying pigments, normally masked by chlorophyll. The Hylocereus rootstock, a climbing cactus, provides the robust base for this unique arrangement.
Providing Essential Care
Ruby Ball Cacti thrive in bright, indirect sunlight, such as near an east or west-facing window. While the green rootstock tolerates some direct sun, the colorful top is sensitive and can scorch if exposed to prolonged intense light. Insufficient light may lead to leggy growth, while too much direct sun can cause discoloration or burnt patches on the scion.
Watering is crucial to prevent rot. Use the “soak and dry” method, allowing the soil to dry out completely between waterings. During the spring and summer growing season, water more frequently, perhaps every two to three weeks, but always check soil dryness. In fall and winter dormancy, reduce watering significantly, often to once a month or less.
A well-draining cactus or succulent potting mix is vital for drainage. This can be a commercial blend or a homemade mix incorporating components like perlite or coarse sand to enhance aeration and drainage. Ensure the pot has adequate drainage holes to allow excess water to escape freely.
Ruby Ball Cacti prefer moderate temperatures, generally between 68°F and 86°F (20°C to 30°C) during the day. They are not tolerant of frost and should be protected from temperatures below 50°F (10°C). As desert plants, they prefer dry conditions and do not require high humidity. Fertilizer needs are minimal; a diluted cactus fertilizer can be applied once a month during spring and summer, but not during dormancy.
Repotting and Potting Practices
Repotting a Ruby Ball Cactus is not frequent, as these plants prefer a somewhat crowded root environment. Repotting is typically needed every two to three years, or when the plant outgrows its current container. Signs include roots emerging from drainage holes or significantly slowed growth. The ideal time for repotting is during the plant’s active growing season, spring or early summer.
When repotting, select a pot only slightly larger than the previous one, ensuring it has proper drainage holes. A pot that is too large can hold excessive moisture, increasing the risk of root rot. Use a fresh, well-draining cactus and succulent soil mix. Gently remove the cactus from its old pot, carefully handling the root ball, and position it in the new container, backfilling with soil.
After repotting, withhold water for about a week to allow any damaged roots to heal and reduce the chance of rot. This helps the plant settle before regular watering resumes. When initially potting a new Ruby Ball Cactus, ensure the container and soil provide excellent drainage.
Addressing Common Problems
Rotting is a frequent issue for Ruby Ball Cacti, primarily caused by overwatering. Signs include a mushy base, discoloration, or a soft, collapsing texture. Ensuring the soil dries completely between waterings is the most effective preventative measure.
The top scion’s vibrant colors can fade or discolor due to improper light exposure. Too much direct sunlight can scorch the colorful top, leading to bleached or browned patches. Insufficient light can cause the colors to dull or the plant to stretch. Adjusting the plant’s location to provide bright, indirect light helps maintain its vibrant hues.
Shrinking or wrinkling usually indicates underwatering or root issues. If the plant appears shriveled, a thorough watering may rehydrate it. If the problem persists, it could signal root damage preventing water absorption. Pests like mealybugs can sometimes affect Ruby Ball Cacti, appearing as small, cottony masses. These can be treated by gently wiping them away with a cotton swab dipped in rubbing alcohol.
Graft failure is a natural limitation for many grafted cacti, including the Ruby Ball Cactus. The top scion and bottom rootstock can grow at different rates, eventually leading to a separation or weakening of the graft union. This can result in the decline of one or both parts of the plant, and is often a natural endpoint for these plants.