Spiral Cactus
Cereus forbesii 'Spiralis'. USDA zone 9b-11b, hardy to 40F. Lives: Back patio, OKC.
About this Spiral Cactus
The Spiral Cactus is a striking columnar cactus prized for its dramatic, twisted stems. Young plants start out growing straight, but begin to spiral once they reach about 4–10 cm tall. Stems are a waxy blue-green with 5–9 sharp-spined ribs, and mature plants can reach 10–16 feet outdoors, though indoor specimens typically stay between 3–4 feet. It is a night-bloomer, producing large white or pinkish flowers that last up to 24 hours, followed by purple or red fruit if pollinated.
This cactus needs at least 6–8 hours of direct sun daily — insufficient light is the most common cause of the spiral loosening or the stem growing straight. Water using the soak-and-dry method, allowing the soil to dry completely between waterings (every 2–3 weeks in summer, once a month or less in winter). Use a sharply draining cactus mix with 70–80% mineral grit such as pumice or perlite. Feed with a diluted cactus fertilizer once a month during the spring and summer growing season.
It is not frost-hardy and prefers temperatures between 70–85°F; bring it indoors if temps drop below 40–50°F. Watch for mealybugs and scale hiding in the spiral crevices — treat with neem or horticultural oil. Brown corking on older stems is normal and cosmetic.