Botanical Name — Gymnocalycium mihanovichii
Plant Family — Cactaceae
Gymnocalycium mihanovichii stands out for its dark surface and geometric ribs. Native to Paraguay, this hardy plant lives its life beneath overhanging brush, where it benefits from consistent filtered light. It never grows taller than about an inch and a half tall, and just a little bit wider.
- Give Gymnocalycium mihanovichii only a little full sun. For most of the day, especially during peak hours of sunlight, it prefers an environment that mimics its native home at the base of an overhanging bush. Bright, filtered light through a sheer curtain is best.
- These cacti thrive in warm temperatures and low humidity. Provide consistent temperatures above 65 ºF.
- They are cold tolerant to just below freezing if kept dry. However, it’s best to move them inside when temperatures drop below 40 ºF.
- Gymnocalycium mihanovichii are drought tolerant. Always allow the soil to dry out completely in between waterings. When you do water, soak the soil thoroughly.
- If you are unsure whether or not the soil is dry, wait a few days before watering. It is much better to underwater than over water. Excessive moisture can quickly lead to root rot.
- Water less frequently in the winter, every month or so.
- These plants prefer a gritty, well-draining mix. Use cactus soil or amend regular potting mix with sand and fine pumice up to 50% to improve texture and drainage. We don’t want this soil to retain water.
- During the warm season Gymnocalycium mihanovichii may produce showy, silky flowers that double the plant’s height temporarily and blossom cream with a yellow center.
- Feed with a high potassium fertilizer in summer twice a month, diluted to half again the suggested amount.
- These plants are typically propagated from seeds, as they seldom produce offsets.
- The best way to prevent pests and diseases is to plant in a well-draining soil and keep the plant in an area that is well ventilated.
- Keep an eye out for red spiders and mealy bugs, both of which can be rubbed off or treated with diluted neem oil.
- Root rot can easily occur if the plant is overwatered, kept in a poorly aerated space, or not provided proper drainage.
Maintenance (pruning, legginess, repotting)
- These hardy plants require very little maintenance. Container grown cacti prefer to be rootbound, so repotting should be necessary only once every three or four years. A larger pot may not be necessary, but a repot with fresh soil could benefit the plant.
- Gymnocalycium mihanovichii have no known toxicity to humans or animals. Spines are sharp so it is advisable to keep out of reach of pets and small children.