What Causes the Failure of Mango Grafting?

Mango trees (Mangifera indica) are prized for the juicy fruits they produce as well as for their ornamental value, with brilliant purple-red new foliage, showy white flower spikes and a dense, spreading canopy. Mangoes, warm-climate trees that survive in U.S. Department of Agriculture plant hardiness zones 10 to 11, are typically propagated by grafting a scion, or portion of the desired parent plant, to a seedling rootstock. Many different factors can cause graft failure.

Only collect scion wood from healthy, vigorous and disease-free parent mango trees. The scion wood selected should be as close in size as possible to the portion of the rootstock to which it will be grafted so it can align well. If scions are allowed to dry out before grafting or are injured by cold, the graft will fail. Mango scion wood loses vitality quickly, so it is ideal to use it immediately after collection. It is possible, but not ideal, to refrigerate mango propagation wood placed in a plastic bag with damp peat moss or sand for about a week.

The mango tree is potentially propagated using veneer grafting, the recommended grafting technique for mangoes, any time during the year that the rootstock is actively growing, but the ideal window for grafting is April through August. Good sanitation practices throughout the rootstock growing and grafting processes are important to prevent disease spread. Use only sharp, disinfected tools and high-quality, disease-free growing mediums. If necessary, mark the upper end of the scions so that you do not attempt to graft the scions upside down.

It is crucial that the cambium, the tissue layer under the bark, on the scion and the cambium of the rootstock align. With a sharp, sterile knife, a slanting cut should be made about 2 to 3 inches long into the rootstock and a second cut at the bottom of the first one to create a notch. Cuts are made into the scion so it will fit exactly into this prepared space and as much of the two cambia will be in contact as possible. Grafters use waterproof rubber electrician's tape or another suitable material to secure the union.

Caring for the union well following grafting is crucial. The union must remain covered so that it does not dry out. However, leaving the tape or other material in place for too long if it does not break down on its own is also problematic, as it can girdle the union. Physical contact, forceful overhead watering, weather or birds may disrupt the union and insects or disease can attack it, too. Excessive light or shading and extreme temperatures or humidity levels can also cause graft failure.