A variety of methods are used to propagate Hibiscus rosa-sinensis. Some of the most common are: Seeds, Rooting, Layering, and Grafting.
Seeds: While most species of Hibiscus can be grown fairly easily from seed, that is not always the case with hybrid cultivars of Hibiscus rosa-sinensis. New hibiscus varieties are developed by crossing (hybridizing) two existing varieties, and then planting the resulting seed. However, many exotic hybrid varieties produce little viable seed, so considerable care must be taken to protect the seed pods and then carefully growing plants from the seed. Hybrid plants, even crossed with themselves, will not reproduce uniform copies of themselves. Only species-type plants will normally produce exact duplicates from seed, and even then occasional “Sports” will occur.
Rooting. Cuttings are rooted in damp materials such as Perlite or sand, or sometimes even in just a container of water. Most “garden variety” hibiscus root easily, and this is a great way to increase a collection. Most hibiscus fanciers are usually glad to share cuttings with other growers.. except perhaps during Show season when pruning means fewer blooms to show!
Layering. This is another type of rooting, in which the branch is bent over and covered with soil. This sometimes happens inadvertently. Roots will form where the branches are in contact with the soil. After roots have formed, the branch is cut off and the new plant is potted or transplanted. Another form of layering is done by wrapping a section of branch in damp material, often spaghnum moss. That is secured with plastic or foil, and the area is kept damp for a few weeks. Roots will generally grow from nodes that were covered with the growth medium. A dab of rooting hormone may improve the speed of root development.
Grafting. In this method of propagation, cuttings (called scions) are taken from a healthy plant, and inserted into cuts or notches made in a hardy root-stock plant. This method is of particular value when dealing with exotic hibiscus that produce great blooms, but do not propagate well by rooting. It is an unfortunate fact that the emphasis on creating stunning show blooms has resulting in the genetic deterioration of many of the plants. Quite a few show-winning hibiscus grow slowly or poorly on their own roots, and such cultivars are nearly always propagated by grafting. The most popular root stock plant in the Houston area is ‘Pride of Hankins’, while ‘Albo’ is more commonly used in Florida.
Note: All of the above methods work with most, but not all, varieties of Hibiscus rosa-sinensis. Some hybrid plants are simply difficult to propagate. Also, any plants that have been treated with growth regulator hormones will generally not respond to propagation efforts until the effect of the hormone treatment has worn off. That may take anywhere from 6 months to a year. (see article: Growth Regulators)
Cloning. Cloning is a popular method of propogating many types of ornamental plants, and has revolutionized the plant nursery industry in recent years. Unfortunately, Tropical Hibiscus do not respond well to this procedure, and no one has yet announced success at cloning Hibiscus rosa-sinensis.