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Gymnocalycium denudatum (Spider Cactus)


Scientific Name

Gymnocalycium denudatum (Link & Otto) Pfeiff. ex Mittler

Common Names

Spider Cactus


Echinocactus denudatus (basionym)

Scientific Classification

Family: Cactaceae
Subfamily: Cactoideae
Tribe: Trichocereeae
Genus: Gymnocalycium


Gymnocalycium denudatum is a small, usually unbranched cactus with a globular, glossy dark green stem, rounded ribs, and spines flattened against the body in the shape of little white or pale rose spiders. The stem grows up to 4 inches (10 cm) tall and up to 6 inches (15 cm) in diameter. Flowers are creamy-white, up to 3 inches (7.5 cm) in diameter, and appear in spring and summer.


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. See more at How to Grow and Care for Gymnocalycium.


Native to Brazil (the Rio Grande do Sul), Uruguay (Melo), and probably Paraguay.


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