Pack Size: 20, 100, 300
Year: 2026
Accepted Scientific Name: Cleistocactus strausii (Heese) Backeb.
Common Name: Silver Torch Cactus, Woolly Torch Cactus
Origin and Habitat:
Cleistocactus strausii is a distinctive columnar cactus native to southern Bolivia, particularly the mountainous regions of Tarija. It inhabits dry, rocky slopes, open shrublands, and high-elevation valleys, where plants grow in well-drained, mineral-rich soils among rocks and sparse vegetation. These environments experience strong sunlight, warm days, cool nights, and seasonal rainfall followed by extended dry periods. The species is adapted to considerable temperature fluctuations and relatively cool mountain conditions. Its dense covering of silvery-white spines provides protection from intense sunlight and contributes to its distinctive appearance. Mature plants often develop multiple upright stems, forming impressive clusters in their natural habitat.
Description:
Cleistocactus strausii, commonly known as the Silver Torch Cactus, is a striking columnar cactus characterized by its upright, cylindrical stems densely covered with fine, silvery-white spines. Mature plants typically reach approximately 48–120" tall, with individual stems measuring 2–3" in diameter. The grey-green stems develop approximately 25–30 narrow ribs, closely spaced with numerous woolly areoles. Each areole produces approximately 30–40 fine, white radial spines and several slightly longer, yellowish central spines, creating a dense, silvery appearance that nearly conceals the green stem beneath.
Plants initially grow as single upright columns but gradually produce additional stems from the base, forming attractive clusters with age. Mature specimens produce unusual, narrow, tubular flowers approximately 2.5–3.5" long, displaying deep rose-red to burgundy colouring. Unlike many other cacti, the flowers remain mostly closed, with the stamens and stigma extending beyond the petals. Flowers emerge horizontally from the sides of mature stems during spring and summer, followed by small, rounded, reddish fruits containing numerous black seeds. Its architectural growth habit, brilliant silver spination, and contrasting red flowers make it a highly desirable ornamental cactus.
Cultivation:
Zone: 9–11; established plants tolerate brief light frost under dry conditions, but protection from prolonged freezing and winter moisture is recommended.
Temperature: Optimal growth at 15–28 °C. Maintain winter temperatures around 5–10 °C under dry conditions. Avoid prolonged exposure to extreme summer heat.
Growth Rate: Moderate under favourable conditions, developing upright cylindrical stems that gradually produce additional basal shoots and form dense clusters.
Soil: A highly mineral, fast-draining cactus mixture containing pumice, fine gravel, and a moderate proportion of organic matter. Excellent drainage and adequate root aeration are essential for healthy growth.
Watering: Water thoroughly during active growth, allowing the growing medium to dry between waterings. Provide adequate moisture during warm growing conditions without allowing the roots to remain saturated. Reduce watering significantly during autumn and keep mostly dry during winter dormancy.
Fertilizing: Apply a diluted, low-nitrogen cactus fertilizer every 2–3 weeks during active growth. Discontinue feeding during winter.
Light: Full sun to bright, filtered sunlight. Strong light encourages compact columnar growth and dense, silvery-white spination. Provide protection from intense afternoon sunlight during extreme heat, particularly for young plants.
Pests and Diseases: Susceptible to mealybugs, root mealybugs, spider mites, scale insects, and root rot associated with excessive moisture or poorly draining growing media.
Germination Info:
Temperature: 27 °C.
Surface Sown: Yes. Sow seeds on the surface of a fine, sterilized cactus growing medium and press lightly into place. A very thin covering of fine mineral material may be used.
Germination Time: Approximately 7–21 days under favourable conditions, although some seeds may require longer.
Moisture: Maintain consistent surface moisture and high humidity during germination, avoiding waterlogged conditions.
Light: Bright, indirect light. Avoid direct sunlight on covered seed trays.
After Germination: Gradually increase ventilation as seedlings establish. Maintain moderate moisture until young plants develop stronger root systems. Introduce brighter light gradually as the seedlings mature and begin developing their characteristic silvery-white spines.
