Gymnocalycium oenanthemum

Gymnocalycium oenanthemum is a species of flowering plant in the family Cactaceae, endemic to Argentina. A slightly flattened sphere growing to 12 cm, it has 10–13 ribs, each containing a row of tubercles with radial spines. In summer it bears a wine-red or pink daisy-like flower.

Description
Gymnocalycium oenanthemum grows individually with cloudy gray-green to blue-green, flattened, spherical shoots and reaches heights of up to 8 centimeters with diameters of 12 centimeters. The eleven to 13 ribs are sharp-edged. There is a central spine, which is often missing. The usually five straight to slightly curved, reddish-gray marginal spines have a darker tip and are up to 1.5 centimeters long.

The short, funnel-shaped, wine-red to slightly pink, shiny flowers reach a length of up to 5 centimeters and a diameter of 4 centimeters. The fruits are green.

In cultivation in the UK and other temperate regions it cannot survive freezing, so at least in the winter months it must be kept indoors in a bright, cool environment with minimal watering. It has gained the Royal Horticultural Society's Award of Garden Merit.

Distribution
Gymnocalycium oenanthemum is widespread in the Argentine provinces of Catamarca and La Rioja at altitudes of 800 to 1300 meters.

Taxonomy
The first description was made in 1934 by Curt Backeberg.