Eulychnia castanea aka Snail Cactus

Eulychnia castanea is a shrubby cactus from coastal Chile. It belongs to the cactus family, Cactaceae. Its range runs from western Coquimbo to northern Valparaíso. Copao de Philippi is one of its local names. It grows on rocky flats, slopes, and in coastal ravines. Long droughts shape this habitat, but coastal fog supplies water. Winter brings most of the rain.

This evergreen succulent forms low clumps with branches from ground level. Reported height reaches about 3.3 feet [1 m]. Its stems reach 1.6–6.6 feet [0.5–2 m] long. They rise at first, then spread or trail over rocks. Large wild thickets can span 66 feet [20 m]. This is not a stated garden spread. Green, round stems have eight to thirteen low ribs. Dark grey felt covers the areoles along each rib. Straight spines range from yellow to brown. Each areole bears six to ten short radial spines. One or two stout central spines grow much longer.

The flowers open by day near the branch tips. They form broad bells with white or pinkish tepals. Each bloom spans about 0.13–0.16 feet [0.04–0.05 m]. Short flower tubes bear scales, brown hairs, and stiff spines. Round, fleshy fruit turns yellow to yellow-green. It reaches about 0.16 feet [0.05 m] across. Scales and spines cover the fruit, with flower remains above. The seeds are small, oval, and black. Local people gather the fruit and eat it raw.

Grow it in a coarse, mineral cactus mix with good drainage. Rich compost can lead to stretched growth. Give light, regular water in summer, then let the mix dry. Keep it dry through its winter rest. Good airflow also matters, since excess water can cause rot. A summer feed high in potassium is recommended. Growth is fairly slow, and plants can form clumps in pots. Growers value its shape as an ornamental. Seeds and offsets provide ways to raise new plants.

Cold tolerance reports differ, so protect it from frost. Useful Tropical Plants calls it frost-intolerant. LLIFLE reports brief survival at 28°F [-2°C] when dry. That source recommends winter rest temperatures of 41–50°F [5–10°C]. The plant has no reported toxic hazards in Useful Tropical Plants. This does not remove the risk from its strong spines. That source lists no known medicinal uses. It also reports a 2017 IUCN assessment of Least Concern. Its range is small, but plants remain abundant in protected areas.