Cleistocactus samaipatanus is a long, narrow, columnar cactus, lime green in color, with 14 to 17 ribs and stiff pale gold spines up to 3 cm long. The plant has several rounded cylindrical, slender ascending, later decumbent, prostrate or pendent, lime green, 90-150 m long and 5 cm in diameter and many-ribbed. The ribs are 14-17, low, rounded up to 2 mm high and 7 mm wide. With Light brown tomentose areoles , the radial spines are stiff pale gold m up to 1.2 inches long..
The brilliant red to pink flowers are up to 2 inches long and up to 1 inch in diameter. The fruits are small, spherical, and reddish with dense white and brown wool, up to 1 cm long and wide. With optimal growing condition it flowers time by time from late winter to nearly autumn.
Bonzi cactus require filtered bright light, but not in full sun that will sun scald it. It need a well drained soil mix. Water regularly in summer but allow to dry fully before watering again. During the winter months they should be rather kept dry. Since they are rapid growers need plenty of space for their roots, repotting should be done every other year or when the plant has outgrown its pot. A slow-release fertilizer applied in the spring will be sufficient for the whole year
This is a beautiful specimen cactus for a large cactus or succulent garden. It can make an interesting plant for a large container and is a nice centerpiece for a warm, sunny courtyard. The plant does have a few spines so care should be taken in its location.