The Peruvian apple cactus is a succulent cactus that can grow up to six feet tall. It requires very little water and grows in full sun or partial shade. To care for your Peruvian apple cactus, keep it well-drained and moist, but not wet. You can also provide it with occasional light fertilization. Prune off any damaged or dead branches in the spring and summer, but do not prune too much off the main stem - leave at least two inches of growth.