Scientific: Cleistocactus strausii (Synonyms: Pilosocereus straussii, Borzicactus strausii, Cephalocereus strausii, Cereus strausii)
Common: silver torch, wooly torch
Family: Cactaceae
Origin: Rocky outcroppings of the Andes mountains in Bolivia south into Argentina at elevations at and above 9,500 feet.
Pronounciation: Cleese-toe-CAC-tus straus-EE-i
Hardiness zones
Sunset 12-24
USDA 8-11
Landscape Use: Strong accent, focal point, xeric and cactus gardens, patio containers, curiosity or novelty plant.
Form & Character: Upright, columnar, erect, stout, interesting, white, wooly, fuzzy, cuddly, yet deceptively dangerous, xeric.
Growth Habit: Evergreen, succulent, strongly upright, sparsely branched at the base, slow growth rate, stems elongated to 10 feet tall, often shorter in Phoenix.
Foliage/Texture: Narrow, light green, strongly pleated stems to 3 inches in diameter, 25 to 30 ribs, areoles densely arranged along ribs, each areole has four yellow-brownish short central spines to 1-inch long and 30 to 40 white radial spines to 2-inch long, radial spines fuzzy, hairy to bristly; medium coarse texture.
Flowers & Fruits: Large, somewhat pubescent, tubular pink to rose red flowers at the stem apex, pistil extended, flowers protrude oddly horizontal and radially from the stem; fruits pear shaped to spherical, reddish.
Seasonal Color: Flowers only on mature plants during late summer and fall, otherwise it's all WHITE.
Temperature: Heat tolerant to only 112oF, suprisingly tolerant of winter cold in Phoenix.
Light: Partial shade best, absolutely avoid western summer sun and western exposures in Phoenix.
Soil: Well-drained soils are best.
Watering: Irrigated sparingly during spring, summer and fall allowing soils to completely dry in between irrigation events, no supplemental water during winter.
Pruning: None
Propagation: Seed, but asexual propagation from callused stem segments is easiest. Cut stems readily regrow.
Disease and Pests: None outdoors except root rot if over irrigated, but mealybugs and spider mites are common when cultivated as a conservatory or greenhouse plant.
Additional comments: Silver torch is a striking and visually captivating columnar cactus. Worldwide silver torch is mostly grown as an indoor novelty or curiousity plant. However, in the lower desert southwest outdoor cultivation is possible. In Phoenix, outdoor culture of silver torch is sometimes difficult (such as during the ridiculously hot summers of 2020, 2023, and 2024) due to it being highly susceptible to summer sunscald and heat stress injury.
