Astrophytum myriostigma var. quadricostatum - Four-Ribbed Bishop’s Cap

Morphological Characteristics

Astrophytum myriostigma var. quadricostatum is a rare and visually striking variant of the classic Bishop’s Cap cactus. Its defining feature is its four vertical ribs (instead of the typical five), giving it a clean, geometric form that appeals to minimalist collectors. The cactus has a smooth, spineless, matte-green to bluish-gray epidermis, often adorned with a fine dusting of white trichomes that resemble tiny stars. This “frosted” appearance gives the plant its genus name—Astrophytum, meaning “star plant.” Each rib is slightly curved and subtly angular, contributing to a sculptural symmetry. The plant typically forms a solitary stem that may slowly elongate over time but retains a compact and tidy silhouette. Mature specimens may grow up to 10–20 cm (4–8 inches) in height and diameter. In late spring to summer, mature plants produce large, satiny yellow flowers with orange centers, emerging from the apex. These blooms add contrast to the otherwise matte-green body.

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Growth Habits

This cactus is solitary and slow-growing, making it ideal for container culture or display in structured arrangements. It does not readily offset and grows with a consistent, symmetrical form that enhances its architectural appeal. Due to its moderate growth rate and drought tolerance, it is perfect for low-maintenance collectors or display in modern interiors with strong lighting.

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Maintenance Points

• Lighting: Thrives in bright light to full sun. A south- or west-facing window is ideal indoors. Outdoors, acclimate gradually to full sun to avoid sunburn.

• Watering: Water deeply but only when the soil is fully dry. During winter dormancy, reduce watering drastically or cease altogether to avoid root rot.

• Soil: Requires well-draining cactus mix. Add pumice, coarse sand, or perlite to improve aeration.

• Temperature: Prefers warm temperatures between 18–30°C (65–86°F). Not frost-tolerant; minimum safe temperature is 5°C (41°F).

• Fertilization: Apply diluted cactus fertilizer during spring and summer once a month. Avoid feeding during dormancy (fall/winter).

• Handling: Minimal handling recommended. Though spineless, the surface trichomes are delicate and easily rubbed off, reducing the plant’s visual appeal.

• Pest Resistance: Generally pest-resistant if grown with proper airflow. Watch for mealybugs and scale insects in dense environments.

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Display & Use

Astrophytum quadricostatum is a premium collector’s plant due to its rare four-ribbed morphology and sculptural simplicity. It excels in:

• Modern and minimalist container displays

• Architectural landscaping with other geometric succulents

• Showcase pots with dark or white contrast glazes

• Bright window displays, especially with natural stone or gravel topdressing

Pairs beautifully with Haworthia, Echeveria lauii, Ariocarpus, and other low-profile, symmetry-loving succulents.