Attractive, showy flowers in shades of red, pink, white or yellow grace the succulent, shrubby desert rose (Adenium obesum). These plants survive outdoors in U.S. Department of Agriculture plant hardiness zones 10 to 12, although they perform well in containers and are cultivated as houseplants or container specimens across a much broader range. Often, one of the most desirable features of a desert rose is its caudex, a thick, swollen area of the stem near ground level. The easiest way to propagate desert roses vegetatively is by rooting cuttings, but it is very difficult to force a desert rose started from a cutting to develop a caudex, so it often preferable to graft a scion, or small piece of a desirable desert rose plant, to a young rootstock. All parts of this plant are toxic, so handle it very carefully; wear protective gloves and cultivate this plant very cautiously, if at all, around small children and pets.
Select a rootstock, usually a young desert rose started from seed that is healthy and has an attractive caudex. Also choose scion wood from a parent plant with desirable flowering and other characteristics. Both the rootstock and the plant from which you will collect scion wood should be healthy, disease-free and vigorous. The scion should have the same diameter as the rootstock about 3 inches above its caudex.
Put on gloves that the desert rose sap will not penetrate and use a sharp, clean knife to cut a scion from young growth near the top of the parent desert rose plant, creating a piece about 5 inches long with a base that has the same diameter as the rootstock 3 inches above the caudex.
Cut the rootstock top off using a horizontal cut to completely sever the stem about 3 inches above the top of the caudex.
Cut into the top of the rootstock, making a vertical cut 3/4-inch deep across the exposed rootstock stem.
Make angled cuts into the bottom 3/4 inch of the scion, forming a wedge that will fit into the cut you made on the rootstock.
Push the prepared scion into the cut in the rootstock, making sure the cambium layers, immediately under the bark, of the scion and rootstock are solidly in contact with each other. You may need to temporarily pry open the cut, or cleft, on the rootstock to fit the scion in snugly.
Wrap the graft union well with grafting tape or coat the entire union area well with grafting wax to keep the union from drying out and failing. Wrap the tape snugly but not too tightly to avoid girdling the desert rose.
Inspect the graft union regularly, making sure that the tape or wax remains intact until new growth emerges from the scion, adding more wax or tape, as needed. Monitor the tape. If it is biodegradable, make sure it begins to break down. If the tape does not break down, cut it off gently within about a year following grafting to keep it from girdling the plant.