Experts and BHG readers answer.
Gardenias root quite easily by taking soft cuttings from the mother plant. These root best using young growth, usually during the summer. Cut new shoots about 4" to 6" inches long, and make a clean cut just below where leaves emerge (the node). Strip the lower leaves off and dip the cut end in powdered rooting hormone, available from the garden center or nursery. Tap off excess and then stick the cuttings in a rooting medium such as coarse sand, perlite, or a peat/perlite mix; water them in carefully. On a small scale you can put them in a clear plastic bag and seal; on a larger scale they do best in a misting bed where the humidity remains constantly high. In plastic, be sure that they are not in direct sun and can be "cooked". Roots should appear in a few weeks, when the young plants can be weaned from the high humidity and potted up.