Cactus and Succulents: Cleistocactus strausii

Origin and Habitat: Garden origin.

Description: It is a slender, erect, columnar group-forming cactus covered with so many silvery-white hairy spines that the green stem is almost completely hidden. It branch profusely from the base.
Stems: The stems are grey-green, slender columns up to 3 m tall , but only about 6 cm across.
Ribs: The "columns" are formed from around 25 ribs.
Areole: Closely set and densely packaged over the stems.
Central spines: Four, thin acicular, yellow-brown up to 40 mm long.
Radial spines: 20-40 usually shorter, fine, bristly 15-50 mm long.
Flowers: This plant is a heavy bloomer and mature cactuses, over 50 cm tall, will profusely produce deep violet-red tubular, slightly curved flowers. The blooms are 6 to 9 cm long and protrude horizontally from the stem on the sides near the tips. In common with other cacti in the genus Cleistocactus, the flowers hardly open, with only the style and stamens protruding. Floral tube with silky hairs.
Blooming season: Late summer. Cultivated plants often flower freely.
Fruits: Pear shaped, red, up to 2 cm in diameter.
Remarks: The nice crested form is very nice and will form large silvery mounds.

Cultivation and Propagation: It is a vigorous and easy to grow plant, and requires, strong sunlight or half shade, but not high temperatures. Water generously during the summer, but allow to dry fully before watering again. During the winter months plants should be rather kept dry. In cultivation, watering too much in winter often leads to root rot. It can withstand hard frosts down to 14°F (-10°C), but the tips might get damaged below 23°F (-5°C). Since they are rapid growers it needs plenty of space for its roots. Repotting should be done every other year, or when the plant has outgrown its pot, and give an occasional high potassium liquid feed. Its silvery spined stems branch from the base and then grow straight upwards towards the greenhouse roof, making a pleasant backdrop for the more numerous globular cacti.
Propagation: It is propagated usually by grafting or sometime by cuttings, but the cuttings will generally not root. If you remove an offset, remember to let it dry for a week or so, letting the wound heal (cuttings planted to soon easily rot before they can grow roots). Rooting usually occurs within 3-8 weeks.