Cleistocactus strausii (Heese) Backeb.
Silver Torch, Silver Torch Cactus, Snow Pole, Wooly Torch
The native range of this species is the high mountain regions of the Department Tarija in Bolivia at elevations between 4,920 and 9,840 feet (1,500 and 3,000 m).
Cleistocactus strausii is a columnar cactus with slender cylindrical grey-green stems with around 25 ribs and densely covered with areoles and clusters of spines. The stems grow up to 10 feet (3 m) tall and only about 2.5 inches (6 cm) in diameter, often branching at the base. Each areole bears 4 yellow-brown central spines and 20 shorter white radial spines. The central spines are up to 2 inches (5 cm) long. Older plants, over 18 inches (45 cm) tall, produce deep red to burgundy flowers in late summer. They are cylindrical, up to 3.2 inches (8 cm) long, and emerge horizontally and radially from the stem.
USDA hardiness zones 9a to 11b: from 20 °F (−6.7 °C) to 50 °F (+10 °C).
How to Grow and Care
Choose a location that gets full sun and has well-draining soil. Water your Cleistocactus during the spring and summer when the top inch (2.5 cm) of soil dries out. During the fall, reduce watering to every five weeks if the ground dries. In winter, keep Cleistocactus dry, or the moist ground combined with the cool temperatures and dormancy may cause the roots to rot. Fertilize Cleistocactus with a low-nitrogen fertilizer during the active growth period. A slow-release fertilizer applied in the spring will be sufficient for the whole year.
It is possible to propagate by cutting a small branch from a Cleistocactus and rooting it, but this inevitably leaves a disfiguring scar near the main stem's base. If an offset is removed to be used in propagation, remember to let it dry for a week or so, letting the wound heal.
See more at How to Grow and Care for Cleistocactus.
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