Gymnocalycium horstii

Gymnocalycium horstii is a cactus species that starts as a solitary plant and usually offset over time, later forms clusters. It has bright green, glossy, spherical stems that grow up to 20 cm in height and diameter. Plants have a squat appearance and spines that are curved back towards the body. The cactus features 5–6 rounded ribs with transverse grooves and usually five yellowish-white spines, up to 3 cm long. One spine points downward, while the others extend sideways. The flowers are creamy white to pale purple-pink, reaching up to 11 cm in length and diameter. Its blue-green, egg-shaped fruits follow the blooms.

This species is native to the southern Brazilian province of Rio Grande do Sul, Uruguay, East Paraguay, and Northeast Argentina growing in rock outcrops and grasslands at altitudes above 300 meters. It has been considered endangered since 2010 due to wild specimens being collected for the plant trade.