Plant propagation is the process of creating a new plant from a part of an existing one. This method uses asexual reproduction, meaning the new plant is a genetically identical copy, or clone, of the parent plant. Unlike growing from seed, which involves the mixing of genes, asexual propagation ensures that desirable traits, such as unique leaf variegation or fruit quality, are preserved. Learning these techniques allows gardeners to multiply their favorite plants, save money, and share their collections.
Cloning with Stem and Leaf Cuttings
Cuttings use pieces of the stem or a whole leaf to trigger new growth. Stem cuttings are effective for many popular houseplants like Pothos and Philodendron, as they already contain a piece of the stem that only needs to form roots. To create a stem cutting, select a healthy piece about three to six inches long, ensuring it includes at least one node—the swollen area where a leaf attaches. The cut should be made cleanly just below a node, and the lower leaves should be removed to prevent them from rotting once submerged or buried.
Applying a rooting hormone, which contains synthetic plant hormones, to the cut end can significantly increase the success rate by encouraging the rapid formation of adventitious roots. Cuttings can be rooted directly in a well-draining soil medium, or temporarily in water, where the process is visible. While water rooting is popular, the roots that form are specialized for water and will need a careful transition to soil.
Leaf cuttings are an alternative method used for plants like Sansevieria or Begonias, where the leaf itself must produce both new roots and a new stem. For example, a healthy Sansevieria leaf can be cut into two- to four-inch segments, and the bottom end of each segment must be inserted into the rooting medium. It is important to note the orientation of the cutting, as roots will only form from the end that was closest to the base of the parent plant. Maintaining a warm temperature, ideally around 71°F, and high humidity can accelerate the rooting process for both stem and leaf cuttings.
Propagating Plants by Division
Division is a straightforward propagation method for plants that naturally grow in clumps, such as Hostas, ferns, and many ornamental grasses. This technique involves separating the parent plant into smaller, independent pieces, each containing a portion of the root system and at least one growing point.
The root ball can often be gently pulled apart by hand into smaller sections, particularly for plants with fibrous roots. For plants with dense or woody root systems, a sharp, clean knife or spade may be necessary to slice the mass cleanly. Each resulting section must have a viable crown bud and sufficient roots to support its new growth. These newly divided plants are then immediately replanted into fresh soil, ensuring the crown is not buried too deep.
Layering Techniques for New Growth
Layering is a low-stress method of asexual propagation because the stem is encouraged to root while still attached to the parent plant. This technique is often successful for plants that are difficult to root from cuttings, particularly woody shrubs.
One common method is ground layering, suitable for plants with flexible, low-growing branches. A flexible stem is bent down until it touches the soil, and a small wound is created on the underside of the stem where it contacts the ground. This wounded section is then secured and covered with soil, and the tip of the stem is left exposed.
Air layering is used for larger, less flexible, or upright stems on plants such as indoor trees. This involves selecting a healthy branch and removing a ring of bark, exposing the inner wood. Moist sphagnum moss or another rooting medium is wrapped around the wounded area, and this entire bundle is covered tightly with plastic sheeting to seal in moisture. Once roots are visible and established within the moss, the stem is cut below the rooted section to create a new, independent plant.
Caring for Newly Propagated Plants
Once a new plant has rooted, it requires a careful transition period to establish itself fully. Cuttings rooted in water need to be “hardened off” when moved to soil because the roots developed in water are structurally different from soil roots. Keeping the soil consistently moist, but not waterlogged, for the first few weeks after potting helps the new roots adjust to the denser medium and prevents desiccation.
Newly transplanted plants often benefit from high humidity to reduce water loss while the new root system is developing. Creating a temporary humidity dome with a plastic bag can help maintain a moist microclimate, but it requires ventilation to prevent fungal issues. The small plants should be placed in a location that receives bright, indirect light, as direct sun can scorch tender new growth. Fertilizing should be avoided until the plant has established a healthy root system and shows signs of new leaf growth.