Gymnocalycium mihanovichii aka Moon Cactus

Gymnocalycium mihanovichii is a small cactus known as chin cactus or plaid cactus. It belongs to the cactus family, Cactaceae, and grows slowly. Its native range covers Paraguay and parts of Argentina. Kew lists Chaco and Formosa within its Argentine range. It grows in a subtropical climate and occurs in rocky places. In Paraguay's Chaco Boreal, it grows beneath bushes. These plants receive direct sun for only part of the year.

The plant has a round body and stays small. NC State gives a height and width of 0.17–0.25 feet [0.05–0.08 metres]. LLIFLE reports smaller plants, about 0.13 feet [0.04 metres] tall. Its reported width is 0.16–0.20 feet [0.05–0.06 metres]. Plants may grow alone or form offsets around the main body. The stem can be dark green, gray-green, or tinged with red. Eight narrow ribs have notched edges. Young ribs form separate chin-like bumps, which flatten as plants age. Each areole bears five or six curved, yellow-gray spines.

Flowers grow from the top of the stem. They have a funnel shape and pale green to brown-yellow petals. Blooms measure about 0.17 feet [0.05 metres] across. They appear from late spring into early summer. Each flower opens during daylight and lasts a few days. LLIFLE notes that the flowers may not open fully. Small, fleshy fruits follow as the blooms fade. These berry-like fruits start gray-green and turn red as they ripen. Ripening takes place in summer or fall. The fruits hold small black seeds.

This cactus suits pots, small spaces, and drought-tolerant gardens. NC State also lists it as a houseplant. Its small size and showy flowers provide its main garden interest. The source lists acidic, loamy soil with good drainage. Its care text calls for light watering and dry soil between waterings. It also calls for less water during winter rest. NC State lists USDA zones 9a–11b. Its care text warns against frost and excess humidity.

Check plants for mealybugs, spider mites, and aphids. Too much water or high humidity can lead to fungal disease. Strong direct sun can scorch the stem. The spines also pose a handling hazard. The supplied sources do not establish whether the fruit is edible. They give no species-level finding on toxicity to people or pets.