Columnar Cacti earned their common name from the slender shape and erect growth habit they exhibit. Several unrelated species are known by the name Columnar Cacti, including Old Man Cactus (Cephalocereus senilis), Firecracker Cactus (Cleistocactus smaragdiflorus) and giant Saguaro (Carnegiea gigantea).
Like most cactus species, Columnar Cacti propagate reliably from cuttings and put down roots in only a few weeks. However, the cuttings often rot if potted immediately after harvest, so it is best to dry them out for at least three days before planting to keep them healthy and productive.
1. Disinfect the blade of a sharp knife using a cotton ball dipped in rubbing alcohol. Lay the knife on a flat surface. Allow the blade dry completely before using it.
2. Select a 3- to 8-inch (7.5 – 20 cm) long piece of Columnar Cactus to root. Make sure the diameter of the cutting is 4 inches (10 cm) or less, because larger columnar cactus cuttings are more difficult to root.
3. Put on gloves to protect your hands. Steady the top of the Columnar Cactus with one hand. Sever the cutting using the disinfected knife. Cut at a 45-degree angle without sawing the flesh of the plant.
4. Place the cutting upside down in an empty ceramic pot so that the cut end is exposed to the air. Set it in a warm, dry spot out of direct sunlight. Allow the end of the cutting to dry out for at least three days, or until the wound heals and takes on a hard, whitish appearance.
5. Fill the bottom half of a plastic pot with a mixture of half pumice and half sterile compost. Nestled the dried end of the Columnar Cactus cutting into the growing mixture. Make sure one-third to one-half the length of the cutting is below the edge of the pot.
6. Hold the cutting upright while filling in around the edges with more of the pumice and compost mixture. Shake the pot slightly to settle the growing mixture. Gently firm the mixture around the cutting. Add more, as needed, to fill the pot to within 0.5 inch (1.2 cm) of the top.
7. Water the columnar cactus cutting two days after potting it. Drizzle water onto the growing mixture until it feels slightly damp at a depth of 2 inches (5 cm). Maintain light dampness in the growing mixture, but allow it to dry out slightly in the top inch before applying more water.
8. Set the potted Columnar Cactus cutting where it will receive very bright but indirect light and temperatures above 68 degrees Fahrenheit (20 degrees Celsius). Shelter the cutting from direct sunlight, which can cause the flesh to dehydrate and make it likely the cutting will die.
9. Check for roots four weeks after planting. Firmly hold the base of the cactus, and gently try to lift it; if the cutting does not yield to the movement, it has produced roots.
10. Transplant the Columnar Cactus cutting into a permanent pot filled with succulent potting mix or directly into a sunny garden bed four weeks after it has rooted. Water it sparingly.
Choose a rooting pot that provides at least 0.5 inch (1.2 cm) of space around all sides of the Columnar Cactus cutting. As an alternative to drying your cutting, try dipping the freshly severed end into gardening sulfur, which also helps prevent rot.
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