Ferocactus viridescens aka San Diego Barrel Cactus

Ferocactus viridescens is a small cactus in the Cactaceae family. Its common names include coast barrel cactus and keg cactus. Its native range runs from southern California into northwestern Baja California, Mexico. It grows in desert and dry shrubland habitats. Records place it from sea level to 656 feet [200 metres]. It is not native to Britain or Ireland.

The plant usually grows as a single, rounded stem. Some stems take on a short, upright cylinder shape. The bright green surface has shallow ribs and curved, yellow central spines. These spines can reach 0.16 feet [0.05 metres] long. The RHS describes stems reaching about 1 foot [0.3 metres]. Its broader garden size range reaches 1.6 feet [0.5 metres] tall and wide. These figures describe a compact plant rather than a tall column. It can take 10–20 years to reach its full size.

The flowers are green, sometimes with a red tint. Each bloom measures about 0.16 feet [0.05 metres] across. Their green tones sit close to the colour of the stem. The RHS classes the plant as evergreen. Its rounded shape, ribs, and spines provide interest beyond the flowers. The RHS lists it for pots and patio displays. Its small size also suits the container use that source recommends.

Under glass, give it bright light filtered from harsh sun. The RHS also lists full sun as a suitable position. Use standard cactus compost and keep the air low in humidity. Its soil guidance includes both loam and sand, with good drainage. Acid, neutral, and alkaline soils all fall within its stated range. Water moderately while the plant grows, then keep it almost dry in winter. During growth, apply a balanced liquid feed every two or three weeks. Its RHS hardiness rating is H1C, allowing summer outdoor use in suitable warmth. The rating's stated minimum temperature band is 5–10°C.

The RHS places this cactus among low-maintenance container plants. It needs no pruning and has no major disease problems listed. Mealybugs can still attack it, so pest checks remain useful. Grow new plants from seed sown in early spring. The RHS gives a sowing temperature of 10–20°C. The supplied species-level evidence does not establish edible parts or toxicity.