Cleistocactus strausii (Heese) Backeb.
Silver Torch, Silver Torch Cactus, Snow Pole, Wooly Torch
Cleistocactus strausii is a cactus with erect, slender, grey-green stems with around 25 ribs and densely covered with areoles and spines. The stems grow up to 10 feet (3 m) tall and only about 2.5 inches (6 cm) in diameter. They have 4 yellow-brown, up to 2 inches (5 cm) long central spines and 20 shorter white radials. Older plants, over 18 inches (45 cm) tall, produce deep red, burgundy flowers in late summer. The up to 3 inches (6 cm) long cylindrical flowers protrude horizontally from the columns.
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 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 out. 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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