Gymnocalycium horstii - Buenekeri Spider

Morphological Characteristics

Gymnocalycium horstii is a striking, globular cactus known for its glossy surface and distinctive spination. The “Buenekeri Spider” nickname likely refers to a specific cultivar or local variant that displays particularly prominent or web-like spine arrangements.

The cactus forms a solitary, rounded body with a glossy, deep green to bluish-green skin. The surface is divided into about 10–13 rounded ribs with shallow grooves between them. Each areole produces short, thick, and slightly curved spines—typically white to pale gray—that contrast beautifully with the smooth epidermis.

Unlike many Gymnocalyciums with subtle or compact features, G. horstii stands out due to its high sheen and symmetrical ribbing. Mature plants can reach 10–15 cm (4–6 inches) in diameter.

The flowers are large and trumpet-shaped, usually white to pale pink, blooming from the apex in summer. These blooms add softness to the cactus’s bold, sculptural look.

Growth Habits

This species is solitary and moderately fast-growing, with a neat and symmetrical form. It may eventually produce basal pups, though it typically grows as a single stem for many years.

Due to its unique appearance and ease of care, it is highly sought after by collectors and hobby growers. It is particularly suitable for indoor pots, minimalist planters, or grouped cactus arrangements.

Maintenance Points

• Lighting: Prefers bright, indirect light to filtered full sun. Avoid intense midday rays without acclimation.

• Watering: Allow soil to dry completely between waterings. Reduce or cease watering in winter dormancy.

• Soil: Requires fast-draining cactus mix. Enrich with perlite, pumice, or coarse sand.

• Temperature: Best grown between 18–30°C (65–86°F). Protect from frost—minimum safe temperature is 5°C (41°F).

• Fertilization: Feed monthly with diluted cactus fertilizer during spring and summer. Avoid fertilizing during dormancy.

• Handling: Spines are mild, making it easier to handle than many other cacti. Avoid excessive handling to preserve surface sheen.

• Pests: Rarely affected, but monitor for scale and mealybugs, especially in enclosed spaces.

Display & Use

Gymnocalycium horstii is a superb specimen for showcasing form and polish. Ideal for:

• Accent pieces in succulent/cactus groupings

• Sculptural containers with high-contrast glazes

• Indoor collections with bright lighting

• Japanese or modern minimalist aesthetics