Of the many ways to propagate the rose of Sharon plant, starting them from seed is just as easy and can be starting near the end of winter, six to eight weeks before the last frost in your area. With loose, moist soil and a sufficient source of light, you can propagate rose of Sharon from seed without much trouble. Once your new plants are outside, they will supply beautiful foliage and luscious flowers to your yard and garden for years to come.
Place your pots into a pan or saucer so each pot rests flat on the bottom. Fill each pot with seed starting mix, leaving a ½ inch of room at the top.
Set a seed in the center of each pot. Add just over a ¼ inch of seed mix over the seed and fill in the pot the rest of the way with sphagnum moss over that.
Pour clean water into the bottom of the tray or saucer and allow the soil in the pots time to absorb the water. Once each pot appears wet at the top, pour off any excess water from the tray or saucer and reposition the pots on the tray.
Slip a plastic bag over each pot, to help hold heat and moisture in the pot and the air surrounding it. Don't seal the bag, but do push it down enough that the opening of the bag is resting on the bottom of the tray or saucer with room above the plant for the seedlings to emerge.
Set the tray in a sunny window or under a grow light and allow it to sit undisturbed for the next two weeks. Add water to the tray only when necessary to maintain a moist soil in the pots.
Take the bags off the pots once your seedlings are about two inches tall. Water regularly when needed to keep the soil moist until the last spring frost has passed in your area, then your plants should be ready to be planted outside.