Rose of sharon, also known as althea or hibiscus syriacus, blooms from summer to fall with large 4-inch flowers in shades of pink, red, blue, mauve and white. The rose of sharon grows well as a tree or shrub. Heavy pruning in the spring increases the flower size but results in fewer blooms. Left unattended, the rose of sharon self-seeds, but for quick propagation, softwood cuttings taken in the spring work well.
Take cuttings from a healthy rose of sharon stock plant in the early morning by making an angled cut from 1/4-inch stems just below a leaf node. The green stem should yield but snap easily when bent. This is known as a softwood cutting. Make the cuttings 6 to 8 inches long.
Remove the bottom leaves from the plant cuttings exposing the lower 3 to 4 inches of the stem. Place the cuttings in water until you are ready to plant.
Moisten potting soil with water until the soil feels like a damp sponge. Fill the growing tray with the soil and form several deep holes by sticking your forefinger all the way into the soil. Put 3 or 4 wooden skewers or stakes at even intervals along the inside edge of the growing tray.
Place 2 to 3 tbsp. of powdered rooting hormone into a small baggie or paper plate. Dip the softwood plant cuttings into the rooting hormone to coat the bottom 3 inches of the stems. Shake off the excess powder and stick the stem cuttings 3 to 4 inches deep into the holes in the potting soil. Tamp down the soil around the cuttings.
Cover the growing tray with clear plastic wrap or a large clear plastic bag to form a humid environment for the plant cuttings. Ensure that the wooden skewers remain in place as the skewers keep the plastic off the cuttings. Seal the plastic completely. Make several small slits in the plastic for air ventilation. Place the growing tray in a bright location but not in direct sunlight.
Monitor the rose of sharon cuttings daily and remove any dead or dying cuttings. Immediately remove any cuttings showing signs of mold. Allow the cuttings to remain in the growing tray for 6 to 8 weeks before checking for root development. The first sign of root growth is a slight resistance when you gently pull on the leaves of the softwood cuttings. Remove the plastic when roots start forming.
Continue growing the cuttings in the growing tray for another 2 to 3 weeks before transplanting the new plants into individual containers. Move the containers into direct sunlight gradually over the next 2 to 3 weeks, taking care to maintain a moist soil medium. When new growth appears on the rose of sharon, transplant the new plants into their permanent home in the garden.