Crepe myrtle, a popular flowering woody shrub or small tree, is commonly propagated using stem cuttings to create genetically identical new plants. This method, known as asexual propagation, is a reliable way to reproduce a favorite variety. While it is possible for a cutting to root in a simple jar of water, this technique is generally not the most dependable or recommended method for successfully growing a long-term, healthy woody plant.
Selecting and Preparing Cuttings
Successful propagation begins with selecting the proper wood at the correct time of year. Semi-hardwood cuttings offer the best outcome, as they are taken from the current season’s growth that has matured but is not yet fully woody. The ideal time to harvest these is typically from late spring through mid-summer (May through August).
Each cutting should be approximately six to eight inches long and contain at least three to four leaf nodes. Roots will preferentially emerge from these nodes. Remove all but the top one or two leaves to reduce moisture loss through transpiration.
Make a clean, angled cut just below a node at the bottom of the stem. Rooting hormone significantly increases the speed and success rate of root formation. The cut end should be dipped in a powdered or liquid hormone before being placed in the chosen rooting medium.
Rooting Cuttings in Water
To attempt rooting in water, prepared cuttings are placed in a container filled with fresh water. Position the container in a location that receives bright, indirect light, avoiding direct sun that can overheat the water. Change the water every few days to maintain oxygen levels and prevent the growth of algae or harmful bacteria that can cause the stem to rot.
When roots appear (usually within four to eight weeks), they are thin, white, and fragile, having developed specifically for a water-based environment. These water roots lack the necessary structure and root hairs to efficiently absorb nutrients and anchor the plant in soil. This difference is the primary reason why water-rooted cuttings frequently struggle or fail when transplanted into a soil medium.
The transition from water to soil requires a careful “hardening off” process to help the delicate roots adjust to a drier environment. Signs of failure include the stem turning black or developing a slimy texture, indicating rot or fungal infection. If rooting is successful, the cutting must be moved to a fast-draining potting mix soon after roots emerge to promote sturdier, soil-adapted roots.
Preferred Propagation Methods
Professional growers and experienced gardeners opt for a solid rooting medium because it offers a higher success rate and produces stronger, more resilient plants. A soilless mix, such as peat and perlite or coarse sand, is favored for its excellent drainage and aeration. This environment allows for gas exchange, which is necessary for healthy root development and helps prevent fungal issues.
After hormone application, prepared cuttings are inserted into the pre-moistened medium about three to four inches deep, ensuring several leaf nodes are buried. Maintaining high humidity is a key factor, often achieved by covering the container with a plastic bag or dome to create a mini-greenhouse effect. This cover reduces water loss from the remaining leaves, allowing the cutting to focus its energy on growing roots.
The rooting medium should be kept consistently moist but never soggy, as waterlogging will suffocate the developing roots. Roots typically begin to form within four to six weeks, often showing as a slight resistance when gently tugged. Once the cutting has established a robust root system, it can be transplanted into a larger pot or a prepared outdoor rooting bed. It should be kept consistently watered until it is ready for its permanent location in the fall or the following spring.