Of the several fruits belonging to the genus Spondias which are grown in various parts of the tropics, the imbu, although relatively little known, is perhaps the best. It merits cultivation wherever climate and soil are suited to its growth.
1 In Broteria, xiv, January, 1916.
2 Bull. 32, Philippine Bur. Agr., 1916.
The imbu grows spontaneously upon the catingas or dry plains of northeastern Brazil. Rarely is it cultivated, since the wild trees furnish more fruit than can be consumed. It has been planted, however, in a few localities where the wild trees are not found. It was introduced into the United States in 1914, but so far as is known, has not been planted in other countries. In view of its abundance in its native home, it is strange that a fruit of such good quality should have escaped the attention of horticulturists until very recently.
The imbu tree is distinguishable from other growths on the catinga by its low spreading crown, which is often 25 feet in diameter. The roots are swollen (whence the specific name tuberosa), and are said by M. Pio Correa to be used as food in times of scarcity. The leaves are 4 to 6 inches long, with five to nine oblong-ovate leaflets, equilateral or nearly so, subserrate or entire, and from 1 to 1 3/4 inches in length. The small white flowers are borne in panicles 4 to 6 inches long. Like those of other species of Spondias, the flowers are composed of a calyx having four or five segments and a corolla of four or five valvate petals. The stamens are eight to ten in number, the styles three to five.
The fruit is produced on slender stems, mainly toward the ends of the branches. Some trees are so productive that the fruit, when allowed to fall, forms a carpet of yellow upon the ground. In general appearance the imbu may be likened to a Green Gage plum. It is oval, about 1 1/2 inches in length, and greenish yellow in color. The skin is thicker than that of a plum, and quite tough. The flavor of the soft, melting, almost liquid flesh is suggestive of a sweet orange. If eaten before it is fully ripe, the fruit is slightly acid. The seed is oblong and about 3/4 inch in length.
Fig. 23. Fruiting twig of the imbu (Spondias tuberosa). (X about 1/3)
In its native home the imbu is eaten as a fresh fruit, and also furnishes a popular jelly. It is used besides to make imbuzada, a famous dessert of northern Brazil. This is prepared by adding the juice of the fruit to boiled sweet milk. The mixture is greenish white in color and when sweetened to taste is relished by nearly every one.
While the tree is susceptible to frost, it cannot be considered strictly tropical. In south Florida young plants have withstood temperatures of 28° above zero without serious injury. Little is known regarding its adaptability to various soils and alien climates. While the wild trees are found on very dry soil in a region of little rainfall, it is possible that other conditions will prove suitable. A few bearing trees were seen by the writer in the city of Bahia, Brazil, where the humidity is great and the annual rainfall about 60 inches. In south Florida it has been tried at Miami, but has not done well. Its failure there has been attributed to the large amount of lime contained in the soil, but it is not certainly known that this is the limiting factor. The soil on the Brazilian catingas is a gravelly loam, sometimes mixed with clay, sometimes sandy.
Fruit from the wild trees varies in size, color, and quality. It should be easy to propagate the best seedlings by cuttings; at least, other species of Spondias are propagated in this way. Mature wood is used. At Miami, Florida, the imbu has been inarched on the ambarella (see below). Seeds are easily induced to grow, and should be germinated in flats or boxes of light soil.