Seeds: There are two distinct seed types among mango cultivars. Mangoes originating on the northern plains of India, in Florida, Israel and South Africa generally have seeds with a single embryo and are called monoembryonic. The single embryo is the result of cross-pollination, a sexual process, and combines the traits of the male and female parents. Seedlings of monoembryonic mangoes will differ from the parent tree. Mangoes originating in Southeast Asia generally have seeds with multiple embryos, and are called polyembryonic. One embryo is of sexual origin, while the other embryos come from the maternal tissue and are identical to the mother tree. Polyembryonic cultivars have traditionally been grown from seed in many countries.
Regardless of the seed type, a seedling tree will take longer to produce fruit and usually will be more difficult to manage, compared to a grafted tree. Therefore, it is generally not recommended to grow mango trees from seed, unless one wants to produce hybrids for purposes of cultivar improvement. For South Florida we recommend as a rootstock 'Turpentine'.
Grafting: Grafting is the most reliable and economical means of propagating the mango. It consists of transferring a piece of a mature, bearing tree (scion) to a separate seedling tree (rootstock), forming a permanent union. The scion forms the canopy of the tree, while the rootstock forms the lower trunk and roots.
Healthy, vigorous and uniform seedlings from polyembryonic seed should be used as rootstocks. Monoembryonic seeds are not recommended for use because their sexual embryos produce non-uniform seedlings. The seed should be removed from the leathery husk and planted at a depth of 12.5 mm (½ in) in nursery trays for later transplanting, or directly in a 3.8l (1 gal) growing container. A standard nursery soil mix can be used provided that it has good drainage. The rootstock should be fertilized, watered and grown to the diameter of a pencil prior to grafting.
Scions can be collected when the trees are in active growth. Scions are obtained by removing the terminal 5 to 7.6 cm (2 to 3 in) of a twig whose terminal bud is beginning to enlarge. Tender terminal shoots can be used for specialized grafting and budding techniques. Scions are removed from the tree and for veneer grafts all of the leaves are removed. For cleft grafts and other specialized techniques, a few of the leaves may be left on the scion. The scions can be placed in a plastic bag and stored at a temperature of 10°C (50°F) for up to 10 to 14 days. Scions can be stored in a home refrigerator, but they must not be allowed to freeze.
Grafting techniques: Grafting should be done in the warmest months of the year with night temperatures above 18°C (64°F). Many grafting methods are successful with mango, including cleft grafting, chip budding and whip grafting; however, one of the most versatile and reliable is the veneer graft.
Grafting height on the rootstock will not influence success or failure. The terminal bud of the rootstock is removed and on both the scion and the rootstock a veneer cut is made. The veneer cut is shallow and exposes the cambium, the active growth region of both the scion and the rootstock. A short flap of bark is left on the bottom of the veneer cut on the rootstock to secure the scion in place.
The two cut surfaces are brought together and then wrapped with plastic grafting tape. Generally the terminal bud is left unwrapped to allow for growth of the bud. Under extremely dry conditions, the terminal bud may be completely covered to reduce water loss, but the plastic must be removed later. The newly grafted tree should be placed in the shade and not exposed to direct sunlight. The graft should begin to grow in 10 to 21 days. The rootstock is cut immediately above the graft following the second vegetative flush of the scion. Following grafting, any shoots from the rootstock must be removed, as these shoots may overcome the developing scion.
For more information, be sure to pick up the book Tropical Mangos “How to grow the world’s most delicious fruit” by Richard J. Campbell, Ph.D and Noris Ledesma.