Mamey Sapote Propagation
From the Horticultural Sciences Department, Florida Cooperative Extension Service
Institute of Food and Agricultural Sciences, University of Florida
Mamey sapote is difficult to propagate vegetatively; however, with proper attention to detail and repeated effort, a high rate of success can be achieved. Grafted trees should not be allowed to become root-bound as this may lead to poor or slow establishment after planting. This can be avoided by repotting into larger containers as tree size increases.
Mamey sapote is commonly propagated by seed in many areas; however, this method is not recommended because seedling trees take 7 or more years to begin fruiting and the fruit quality may be poor. In Florida, seedlings are typically used as rootstocks for desirable cultivars.
Seeds should be collected from mature fruit and planted immediately in well-drained media. Seeds lose viability within 7 to 14 days and there is no good method for storing seeds. Seeds which have a hairline crack in the seed coat appear to germinate more quickly. However, seeds without a crack will germinate satisfactorily. The seed coat can be cracked by placing seeds between two boards and gently applying pressure on the seed until a hairline crack is formed. Seedlings, if grown in beds, should be transferred to containers as they grow and should be ready to graft after 6 to 18 months when trees are 3 feet (about 1 m) tall.
Grafting and Budding
The two most important factors to consider in grafting mamey sapote are time of year and scion preparation. The best time of year to graft mamey sapote in Florida is when there are warm days, cool nights, and low relative humidity. This corresponds to conditions found from March to May and October to November. However, some experienced nurserymen cleft graft during summer and some graft year-round.
Selection and preparation of scionwood is essential for inexperienced grafters, however, for some professionals it is not necessary.
Terminal branchlets are commonly used by commercial propagators. Preparation of this scionwood for grafting involves girdling the branchlet 10 to 12 inches (25.4 to 30.5 cm) below the terminal, 2 to 3 weeks before grafting is to take place. Removal of the leaves, leaving a small section of the petiole will stimulate growth of the buds found in the leaf axils. After budwood is removed from the tree it will be useful for grafting for 5 to 7 days. However, grafting should be done as soon as possible.
An alternative, which produces scionwood with a greater probability of grafting success is to produce new, young shoots by selectively pruning back mature limbs of desired cultivars. The pruning stimulates growth of numerous vigorously growing lateral shoots. These shoots are "juvenile-like" because of their rapid growth and lack of flowering. The terminal 8 to 12 inches (20.3 to 30.5 cm) of this "juvenile-like" growth is the best scionwood.
Removal of the apical bud of the rootstock about 24 to 48 hours prior to grafting enhances grafting success during warmer, more humid times of the year (i.e., spring and summer).
Modified veneer graft. Veneer grafting is a common method used for grafting mamey sapote. Scionwood should be collected and used the same day. In the spring, select shoots on which the terminal buds have hardened and are just beginning to grow. If terminals are not hardened off, subterminal scionwood can be prepared by removing the terminal bud and waiting until lateral buds begin to grow.
Scionwood should be 2 to 4 inches (5.1 to 10.2 cm) long. To graft, make a shallow cut 4 to 6 inches (10.2 to 15.2 cm) long through the cambium layer being sure not to include any wood. Then an oblique cut is made on the reverse side of the scion. On the rootstock at 4 to 8 inches (10.2 to 20.3 cm) above the soil line, a shallow cut of similar length and diameter is made with a small flap of tissue left at the bottom of the rootstock to cover the oblique cut on the scion. After the scionwood and stock are joined, grafting tape (polyethylene is best) is used to wrap and completely cover the scion. Place the plant in about 50% shade. Usually the graft union will form in 3 to 7 weeks at which time tape can be gradually removed from those buds that have begun to grow. Grafted plants may then be exposed to increasing sunlight.
Cleft grafting. For scionwood, select young non-hardened terminals 2 to 4 inches (5.1 to 10.2 cm) long and remove two thirds of each leaf. To graft, cut the rootstock off at 6 to 8 inches (15.2 to 20.3 cm) above the soil line and make a vertical cut into the rootstock 1 to 2 inches (2.5 to 5.1 cm) long, splitting the rootstock in half. On the scion stick make two tapering cuts of similar length that end in a wedge (or V).
Place the scion wedge into the vertical cut of the rootstock, matching cambial layers. Wrap the graft with grafting tape. Next, either cover the scion and rootstock shoot with a polyethylene bag and place in 50% shade, or place the plant in an intermittent mist bed (3 seconds mist every 3 minutes) with 50% shade until the scion begins to grow. After the bud graft union has formed and the graft begins to grow (4 to 6 inches; 10.2 to 15.2 cm) it may be exposed to increasing sunlight.
Budding. Mamey sapote may be propagated by T- and chip budding, however, the level of skill needed for success is much greater than with grafting.
Top-working of established trees to more desirable cultivars is difficult though possible. Trees to be top-worked are pruned back to main scaffold limbs or stumped. The main limbs and stump should be white washed with a 1:1 mixture of water and water-based latex paint. This will prevent the exposed limbs and trunk from sunburning. After new shoots have emerged, several are selected for modified veneer grafting with the desired scion cultivar.
Alternative methods sometimes used by inexperienced propagators include the four-flap and approach grafting methods. While successful, these methods are somewhat cumbersome. Air layering and tissue culture have not been successful and are therefore not recommended.
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Balerdi, Carlos F., Crane, Jonathan H. and Maguire, Ian. "Mamey sapote Growing in the Florida Home Landscape." edis.ifas.ufl.edu. This document is FC-30, one of a series of the Horticultural Sciences Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. First published Apr. 1979. Major revision May 1996 and Sept. 2005. Revised Oct. 2008. Reviewed July 2013. Web. 12 June 2015.
Published 12 June 2015 LR. Updated 18 May 2016 LR