I have a cereus cactus that has...

Cereus cacti have spectacular, fragrant blossoms, but they aren’t known for blooming very often. We don’t think the legginess has anything to do with your plant’s inability to bloom, but perhaps you can trim some of the excess growth back and root the cuttings. To get your cactus to bloom annually, give it a mixture of equal parts water and 20-20-20 fertilizer monthly during the spring and summer. Don’t feed it at all during the fall and winter, and let the plant go a bit dry between waterings. Since this plant prefers to be root-bound, don’t repot it too often.