Propagating Rootstock and Grafting Hibiscus By Jeff McMullan, Steve Hresko, and Jerry NormanBeautiful hibiscus blooms are a joy to many gardeners in our area. Unfortunately, few of the hundreds of hibiscus varieties are readily available. Most varieties are difficult to propagate from cuttings or grow poorly on their own roots. There are other varieties, however, that root easily from stem cuttings and grow vigorously on their own roots. The good news is that hibiscus are relatively easy to graft and patented varieties are few. Desired varieties can be grafted and grown on vigorous rootstock by almost anyone. Though there are many variations in propagating rootstock and grafting hibiscus, the techniques described below are expected to yield the greatest success rate for the novice horticulturist.
The variety “Pride of Hankins” meets our requirements as hibiscus rootstock since it is easily propagated and produces vigorously growing plants. They do well as landscape plantings in our area, producing attractive dark green foliage and many beautiful “hot pink” blooms plus an abundant supply of wood for stem cuttings. (While not winter hardy, the plant will often grow back from its roots if it had been left unprotected from the cold.) Stem cuttings root most easily in the spring, but we have had success year around. While there are much more sophisticated techniques, we simply place 20 or so pencil-sized cuttings in a one-gallon container of light potting mix. Carefully remove the larger leaves and make a diagonal cut through a bud at the bottom of the cutting before setting it upright about 2 inches deep into the potting mix. We sometimes scar the bottom inch or two of the cutting with a knife or pruner blade to expose green wood and stimulate root growth. Rooting hormone is not necessary, but it surely doesn’t hurt, especially if it contains a fungicide. The pot of cuttings is soaked in water and then cared for in light shade by watering daily. In about six weeks the rooted cuttings are separated and repotted in one gallon or smaller pots. After a few weeks in light shade the plants are ready for full sun. A scion of the desired hibiscus variety should be the same diameter or smaller than the main stem of the rootstock. It should be four or five inches long and have two or three healthy buds. Using a sharp knife cut the bottom so that it resembles a lopsided wedge (one side longer than the other as in Figure I). It is easier than you might think to get the scion upside down, so study it for a moment before beginning your cuts. The shorter side should be about 1/3 the length of the longer cut. The sides of the wedge must be flat to achieve maximum contact with the rootstock. We will usually leave one small leaf on the scion as an indicator of graft success. If it remains green after a week or so, the scion is receiving nourishment from the rootstock and the graft has likely taken. Strong vigorous plants with firmly established roots are selected for grafting rootstock. The graft should be made approximately 5” above the soil on the main stem. That way, if your first attempt is unsuccessful, you will have sufficient rootstock to try again below the failed graft. It is sometimes helpful to remove the plant from its pot to gain easier access for grafting, but work quickly so as not to allow the roots to dry out. Prepare the rootstock by first making an angled cut down into the stem (Figure II). This cut should be less than half way through the stem. Continue the cut down the length of the rootstock until it creates a flap that is equal in length to the long cut on the scion. Finish preparing the rootstock by removing nearby shoots and leaves. Insert the prepared scion into the rootstock with the longer cut on top (Figure III). Since it is practically impossible to have precise alignment on both sides, assure that the green cambium layer of the scion is aligned with the cambium layer of the rootstock on one side or the other. The flap on the rootstock can be trimmed to match the short cut on the scion to yield a cleaner looking union on the grafted plant. The scion must be held securely in place while the graft heals. There are various ways to accomplish this. We use rubber budding strips or a piece of wide rubber band stretched and wrapped around the graft. Start wrapping below the graft by overlapping the end of the budding strip. Squeeze closed any gaps with your fingers and stretch the strip as you wrap the entire length of the cut in the rootstock. As you near the top, place the rootstock in your hand with your thumb holding the wraps in place. Make a final wrap around the rootstock and scion. Then capture the rubber strip beneath the last wrap (Figure IV). Remove all leaves and shoots from the rootstock below the graft. Next, the new graft is sealed using grafting wax applied with a small glue brush (Figure V). The wax is melted in an inexpensive electric glue pot (sold at hobby stores) and then allowed to cool to 120 degrees or so before use. It should be liquid but not be too hot to test on your wrist as you would a baby’s bottle. Be sure to fully seal inside the “Y” between the scion and rootstock. Trim the scion back to ½” above the top bud and seal the cut with wax. Prepare and attach a permanent label with the name of the variety, the name of the rootstock, the date the graft was made, etc. Keep the plant watered and in light shade as the graft union heals. In four to six weeks a successful graft will have grown new leaves. During this period, remove any new growth that appears on the rootstock above or below the graft. Once the scion has put on several leaves, cut off the rootstock at an angle just above the graft and seal the cut with Elmer’s Glue-AllÔ glue or just wrap the graft union with Parafilm MÔ. Later, you can peel off the remains of the wax and budding strip when it degrades or just let it fall off on its own. Fort Bend Master Gardeners June, 2002 |
Rootstock - Grafting 
