Frailea castanea | Frailea asterioides | Crested | Large-sized

Scientific Name

Frailea castanea Backeb.

Geographic & Climate

• Geographic Coordinates: Approx. 29°50'S – 31°30'S, 53°40'W – 57°10'W (Southern Brazil: Rio Grande do Sul; Northern Uruguay)

• Climate Classification: Humid Subtropical Climate (Köppen Cfa)

• Habitat Characteristics: Altitude approx. 100–350 meters above sea level. Inhabits stony grasslands (Pampa biome), growing exposed or partially shaded on thin, gravelly, sandy, well-draining acidic soils with well-distributed annual rainfall (1,200–1,500 mm) and distinct warm-summer/mild-winter temperature fluctuations.

Botanical Morphology

• Diagnostic Features: Solitary, flattened-globose to button-like discoid stem reaching 1.5–4 cm in diameter and up to 1.5–2 cm in height. Body color ranges from dark reddish-brown, reddish-chocolate, to dark purple-green. Features 8–14 flat, broad, low ribs separated by fine superficial vertical grooves. Areoles carry 3–8 tiny, short (1–2 mm), dark brown to black appressed spines that curve back against the plant body, giving an insect-like appearance. Flowers are pale yellow (2–2.5 cm wide), strongly cleistogamous (frequently self-pollinated without opening unless temperatures are exceptionally high).

• Growth Habit: Very slow-growing dwarf geophyte. Enters dry/cold winter dormancy. Maximum mature diameter rarely exceeds 4–5 cm.

History & Etymology

• Etymology: The generic name Frailea honors Americo Fraile, a former curator of the cactus collection at the National Department of Agriculture in Buenos Aires, Argentina. The specific epithet castanea derives from Latin castaneus (chestnut), referring to the distinctive dark chestnut-brown coloration of the plant body.

• Historical Context: Formally described by German botanist Albert Frederik Hendrik Backeberg in 1936. Long known in horticulture under the synonym Frailea asterioides Werderm., this species became widely popular among cactus collectors due to its unique sea-urchin-like geometry and dark button-like appearance.