Supertunias are a specific, branded series of hybrid petunias known for their vigorous growth and continuous, self-cleaning bloom cycle. They were genetically engineered to be sterile, meaning they do not produce viable seeds, which allows the plant to focus its energy on flowering rather than on reproduction. Because they are hybrid cultivars, the resulting plants would not grow “true” to the parent, potentially losing the desirable color and mounding or trailing habit. Propagating Supertunias by cuttings is the only method to create genetically identical clones of the parent plant.
Essential Tools and Timing
Successful propagation begins with gathering the right materials and selecting an optimal time for the process. You will need a clean, sharp cutting tool, such as a razor blade or bypass pruners, which should be sterilized with alcohol or a bleach solution to prevent the transmission of plant diseases. The use of a rooting hormone, available in powder or gel form, is highly recommended as it contains auxins, which stimulate the formation of new roots. For a rooting medium, select a sterile, well-draining mix like perlite, vermiculite, or a specialized seed-starting blend to minimize the risk of fungal issues.
The best time to take Supertunia cuttings is typically in late spring or early summer, when the parent plant is actively growing and the weather is warm. Propagating during this period allows the newly rooted plants sufficient time to establish themselves and grow into a substantial size before the end of the season. Cuttings can also be taken in mid-summer during a routine pruning, or even in late summer if the goal is to overwinter the new plants indoors.
Step-by-Step Guide to Taking Cuttings
The process starts with selecting the proper stem material to ensure rooting success. Look for healthy, non-flowering stem tips that are firm and green, as woody stems or those with blooms will divert the plant’s energy away from root production. Using your sterilized tool, make a clean cut on the stem approximately one-quarter inch below a leaf node. This node is the point where the highest concentration of root-forming cells is located.
Prepare the cutting by removing all leaves from the lower two-thirds of the stem, leaving only two to four leaves at the top to facilitate photosynthesis. Any flower buds or open flowers must also be pinched off. Dip the cut end immediately into your rooting hormone powder or gel, ensuring the node area is fully coated, and then gently tap off any excess. Using a pencil or small dowel, make a hole in the moistened rooting medium to prevent the rooting hormone from being scraped off as you insert the cutting.
Gently place the prepared cutting into the hole so the lower node is covered by the medium and lightly firm the mix around the stem to ensure good contact. To create the high humidity environment necessary for root development, place the container in a propagation dome or cover it loosely with a clear plastic bag. The cuttings should be kept in a bright location that receives indirect sunlight and a consistently warm temperature, ideally around 70°F. Roots will typically begin to form within two to three weeks.
Transitioning Rooted Cuttings to the Garden
Once new growth appears on the cutting tips, and you feel slight resistance when gently tugging on the stem, it indicates that a root system has successfully developed. This new growth signals that the plant is transitioning from relying on stored energy to actively taking up water and nutrients. At this point, the young plants are ready to be moved out of the high-humidity environment and begin the process of hardening off.
Hardening off involves gradually acclimating the young plants to the harsher outdoor conditions of wind, intense sun, and lower humidity to prevent transplant shock. Over a period of seven to ten days, introduce the cuttings to the outdoors for a few hours each day, starting in a sheltered, shaded location. Increase the duration of exposure and the amount of direct sunlight slightly each day until the plants can tolerate a full day outside.
After hardening off, the new Supertunias can be transplanted into their final container or garden bed. When planting, gently loosen the roots and place the plant at the same soil level as it was in the rooting container. Supertunias are heavy feeders, so the newly established plants benefit from a consistent watering schedule to keep the soil evenly moist and a diluted dose of a balanced liquid fertilizer to encourage vigorous growth and continuous blooming.