Gymnocalycium stellatum (Speg.) Speg.
Gymnocalycium stellatum subsp. stellatum, Gymnocalycium asterium, Gymnocalycium obductum
Gymnocalycium stellatum is a beautiful, slow-growing cactus with a noticeably flatten body, at first solitary, later clustering. The stem is dark grayish-brown to olive green, flattened globose, with 7 to 11 ribs and up to 4 inches (10 cm) in diameter. The spines are 3 to 5, dark brown, becoming grey with age, straight to slightly curved and flattened against the stem. The flowers are creamy-white with a dull red throat, up to 2.6 inches (6.5 cm) long and up to 1.8 inches (4.5 cm) in diameter. They appear in late spring.
USDA hardiness zones 9b to 11b: from 25 °F (−3.9 °C) to 50 °F (+10 °C).
How to Grow and Care
Some Gymnocalyciums are shade-seeking in the wild, among shrubs or grasses, while others grow completely exposed. Some will therefore need a light shading from the sun in the hottest months, but to overdo this will result in loss of flowers.
The balance of the potting medium should be sufficient to allow good drainage, so that the plants do not sit in soggy soil for more than a day or two after watering.
Watering in the summer months, while the plants are growing well can be frequent (weekly for small plants in small pots), but always allowing the compost nearly to dry out before rewatering. Watering in the winter months at all is unwise and certainly not necessary. The difficult times are spring and autumn.
Those species which produce offsets can be readily propagated by cuttings. Gymnocalycium seed germinates well when fresh and will keep for a few years if stored in cold conditions.
Learn more at How to Grow and Care for Gymnocalycium.
Gymnocalycium stellatum is native to Argentina.
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