Cutting the top off a cactus and replanting it, a process known as “beheading” or “topping,” is a common and reliable technique. This method is used to propagate new plants or salvage an existing one. By removing the upper section, which contains the apical meristem, you create a cutting that can develop its own root system. This procedure allows you to essentially restart the plant, potentially leading to two healthy cacti from one original specimen.
Reasons for Topping a Cactus
Gardeners behead cacti to correct poor growth, disease, or for propagation. A primary motivation is saving a plant where rot has begun in the lower stem or root system. If the rot is caught before it spreads to the upper, healthy tissue, removing the top section ensures the plant’s survival.
Etiolation, caused by insufficient light, is another frequent reason. The plant’s stem stretches and thins dramatically, creating a weak section that will never revert to a healthy stem. Beheading removes this damaged part, allowing you to re-root the robust growth above it. Topping is also a simple way to propagate tall columnar cacti, creating multiple clones and promoting new growth on the remaining base.
Making the Cut and Preparing the Cutting
The first step requires a clean, straight cut through the stem, best achieved using a sharp, sterilized knife or razor blade. Sterilizing the tool with rubbing alcohol prevents introducing bacteria or fungal spores into the open wound. The cut should be perpendicular to the stem, ensuring the largest surface area for callousing and future root growth.
Immediately after the cut, the cutting must be left to “cure” in a dry, warm location away from direct sunlight. This curing process is mandatory because the open wound must form a protective, dry layer called a callus. Without this seal, the cutting is susceptible to rot and infection once placed in soil. Callousing can take a few days for thin cuttings up to four weeks for thicker stems; do not proceed until the cut end feels completely dry and firm.
Replanting the New Section
Once the callus has fully formed, the cutting is ready to be planted in a well-draining medium, such as a specialty cactus or succulent soil mix amended with pumice or perlite. The calloused end should be placed only slightly into the soil, just deep enough to remain upright. For taller, unstable cuttings, use stakes or stones to hold the plant steady in the pot.
During the rooting phase, avoid watering the cutting entirely. The cutting must use its stored moisture reserves to prompt the growth of new roots, a process called adventitious rooting. Watering before roots are present will lead to rot. Place the potted cutting in bright, indirect light, as intense sun can scorch the unrooted plant.
Care for the Original Base
The remaining bottom section, often called the mother plant, should not be discarded. The cut surface will form a protective callus and then begin to produce new offsets, or “pups,” from the areoles below the cut line. Removing the apical meristem releases inhibitory hormones, allowing dormant lateral buds to activate and form new growth.
Unlike the unrooted cutting, the original base still has its established root system and requires continued, reduced care. Allow the cut to heal for a week or two before resuming the regular watering schedule. Over time, the base can sprout multiple new heads, resulting in a bushier, multi-stemmed plant.