The green sapote (Calocarpum viride Pittier) is indigenous to the highlands of Central America, where this handsome large tree, with dark green foliage, reaches a height of about 40 feet. It is considered by many to be one of the best of the Sapotaceous fruits. Appearance-wise, it resembles the mamey sapote (C. mammosum) to which it is closely related. Features distinguishing the two are the green sapote's smaller leaf size, its satiny, brownish pubescence covering the midribs and veins of the undersides of the leaves, its slightly wavy leaf appearance, its rougher-textured bark of the trunk and its smaller fruit. Young seedling trees, lacking these differences which develop with age, can be difficult for the uninitiated to identify from its near 'look alike twin', the mamey sapote.
A search of records for early introductions reveals that Reasoner Brothers (Royal Palm Nurseries) 1887-88 catalogue offered a number of Sapotaceous fruits including the mamey sapote but no mention is made of the green sapote. The first U. S. D. A. green sapote introduction was made in 1913 under the botanical name of Achradelpha viridis, to be followed by five additional introductions of the same fruit in 1914. No record of their trial at the Miami, Florida U.S.D.A. Stations was found. Further seed introductions, which were listed at the Miami U.S.D.A. Stations, were made in 1916, 1929, 1941 and 1944. These reached a total of 157 seeds, none of which lived to become bearing trees.
In 1929 the new name of Calocarpum viride replaced the former botanical name of Achradelpha viridis on the station's records.
Green sapote introductions at the Sub-Tropical Experiment Station in Homestead, Florida started in 1934 with a shipment from Honduras. This was followed by three introductions in 1946 and one each in 1948, 1950, 1956, 1959 and 1962. While all those made prior to 1956 failed to survive, Ruehle (6) reported "Trees 8 to 10 feet tall, growing well at the Sub-Tropical Experiment Station, were killed by flood water in 1948."
From an inspection of the available records, it appears the most frequent single cause for a lack of success with green sapote introduction was the failure of the seed to germinate.
Wilson Popenoe (3) in his Manual of Tropical and Subtropical Fruits published in 1920, reported on page 344 "This species (the green sapote) has been planted recently in California and in Florida. It is more likely to succeed in the latter state than the sapote (mamey sapote), since it is somewhat more frost-resistant. It is doubtful, however, whether it will survive temperatures below 27 or 28 degrees above zero."
Again on page 343 he states: "It is most abundant in Northern Guatemala (the Alta Verapaz), where it grows usually at elevations of 4000 to 6000 feet. Unlike its relative, the mamey sapote, it does not thrive in the hot lowlands. The lower limit of its cultivation is approximately 3000 feet, the upper between 6000 and 7000 feet."
From Popenoe's remarks it would appear that the green sapote would be more cold-tolerant than the related mamey sapote. However Campbell (2) reports, "Young green sapote trees have had higher mortality at this station (Sub-Tropical Experiment Station) than young mamey sapote trees. There is reason to think that they are perhaps less cold-hardy than mamey sapote."
Observation by the writer would tend to confirm Campbell's statement. In the other direction, temperature-wise, the question raised "Is Florida too much like Guatemala's hot lowlands during the summer months?" While this is undoubtedly a factor to be reckoned with, it has not, in certain instances, prevented the green sapote from bearing under South Florida's climatic conditions.
What was believed to be the first instance of the green sapote fruiting in Florida was reported by Whitman and Biebel (7) at the 1962 Annual Meeting of the Florida State Horticultural Society. This related that in November 1954, Dr. Wilson Popenoe, then Director of the Escuela Agricola Panamericana at Tegucigalpa, Honduras, sent the writer scionwood of this fruit which was grafted on seedling stocks of the mamey sapote. In a letter dated December 4, 1954, Dr. Popenoe (4) wrote from Honduras stating, "I suspect that is the first time anyone has made this graft." Of the trees so grafted, one at the Brooks-Tower Nursery in Homestead bore several fruit in the late fall of 1961.
During the autumn and winter of 1964-65, another green sapote, which came into bearing for the first time, put on a performance that would tend to indicate these trees are capable of producing relatively good crops under South Florida conditions. The balance of this report is based upon a preliminary observation of this tree and others growing in Dade County, Florida.
The Green Sapote can be propagated from seed, by grafting either on itself or the related mamey sapote and probably also by marcotting. Whether or not it will graft onto other Sapotaceous fruits is believed untried at present. As the seeds remain viable for only a short time after removal from the fruit, they should be planted as quickly as possible. Removing the hard shell that surrounds the seed, prior to planting aids germination.
In grafting, success has been obtained using a side graft. Scionwood of roughly half an inch in diameter, girdled one or more months prior to grafting has given good results. This is done by cutting through the cambium layer and removing a ring of bark about ½" in width approximately 6" from the end of the selected branch. In addition to this, all leaves except the terminal three or four are cut off. After the girdled branch swells and the dormant buds increase in size, it is ready for grafting. It can then be removed and cut up into shorter piece lengths to make a number of grafts.
The green sapote, when grafted onto small seedling mamey sapote, can be expected to reach a height of approximately 14 ft. or more within ten years and be ready to bear, assuming good cultural conditions. It is believed the same would hold true for the green sapote on its own rootstock, but as yet no known instance of this fruiting crop to be produced by young trees coming into bearing can run close to 75 or more fruit. However this is usually preceded by one or more annual flowerings that fail to set any fruit that holds on to maturity. The small white flowers are born in profusion along the younger branches during late winter or early spring, and cross pollination from other trees is not required for fruit setting.
In Florida, the green sapote fruits from December through March, with the main crop coming in late January. The 'top-shaped' fruit averages 2½" in diameter by 3" long with a thin, brownish-green skin. The sweet, reddish-brown flesh, with a pleasant almond-like flavor contains one or two hard, large, shiny, dark-brown seeds. Fruit picked in advance of ripening on the tree can produce off flavours. In commenting on this fruit, Wilson Popenoe (5) wrote, "It is really superior in flavor to the common sapote (C. mammosum), perhaps more like the sapodilla (Achras zapota). Since it seems like a cross between these two, as far as flavor is concerned, it is known in Guatemala as 'injerto', a hybrid.
When grown on the mamey sapote as a rootstock, the green sapote makes a slightly larger diameter trunk above the graft union. An unidentified disease has been known to attack the graft union area causing extensive die-back above the graft. In one case, what was suspected to be a fungus disease nearly girdled the graft union. Bordeaux mixture made to a paste-consistency with spray oil added as a sticker, was applied after removing the diseased tissue, which resulted in a complete recovery. The green sapote is also subject to attack by the Cuban May Beetle (Phyllophaga bruneri Chapin) which eats the leaves.
Green sapote trees grafted on mamey sapote probably have identical fertilizer requirements to the mamey sapote. Trees so grafted can maintain satisfactory vigor on rich hammock sand soils with little or no fertilizer after reaching bearing size. On the rocky Redlands soils of South Dade, slow decline may set in if an adequate fertilizer schedule is not maintained.
A former source of green sapote trees has been the Brooks-Tower Nursery of Homestead, which propagated these for several years on mamey sapote rootstocks. Seedling green sapote trees, grown from locally-produced seeds, have been offered at the annual plant sale of the Rare Fruit Council of South Florida.
It is suggested that the green sapote could be more widely grown in the warmer areas of South Florida as an attractive dooryard fruit tree, especially since it is winter-bearing at a time when other tropical fruits tend to be scarce. For those fortunate enough to already have a mature mamey sapote tree, graftwood of the green sapote may be added by top -working a part of the tree. By so doing, the one tree can produce both these Sapotaceous fruits and the time taken for the green sapote to come into bearing greatly shortened. The introduction of improved varieties, with fruit up to 5" long, could even further the desirability of this already worthwhile tree.
DATE: March 1991
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