Growing sun cup cactus in a pot

Sun Cup Cactus is well suited to container growing — at about 10 cm mature it is comfortably pot-sized. A container around 12-15 cm (5-6 in) across gives it room without leaving the compost sitting wet, which is the usual mistake when people over-pot a small plant.

Aim for a container 12-15 cm (5-6 in) across. Pot on when roots show through the drainage holes or growth slows noticeably — usually every 1-2 years for a plant this size. Move up one pot size only; jumping several sizes leaves wet compost the roots cannot reach, and that is what rots them.

Sun Cup Cactus needs sharp drainage, so this matters more in a pot than in the ground. Use a free-draining mix (add perlite, grit or bark to standard compost), always pick a container with drainage holes, and never let it stand in a saucer of water.

Containers dry far faster than open ground, so sun cup cactus in a pot needs checking more often than the general guidance of "Every 2–3 weeks in spring and summer; monthly or less in autumn and winter" — especially in summer, wind, or a heated room. Check the top few centimetres with a finger rather than watering on a fixed day.