The ilama is probably the finest annonaceous fruit which can be grown in the tropical lowlands; yet it has not, until very recently, been planted outside the region in which it is indigenous. Now that it has been called to the attention of horticulturists, its range should be extended rapidly to all parts of the tropics.
1 Bull. 1, Div. Pomology.
The identity of the ilama, first mentioned by Francisco Hernandez toward the end of the sixteenth century, remained in doubt until W. E. Safford showed, in 1911, that it was a species which had not been described botanically. Safford named it Annona diversijolia, and brought together much information concerning its habits and the character of its fruit. These data were published in the Journal of the Washington Academy of Sciences, March 4, 1912. More recently the writer has been able to study the species in Mexico and Guatemala, and the United States Department of Agriculture has distributed several thousand plants in the warmest regions of the United States and in tropical America.
The tree grows to an ultimate height of 25 feet. It is slender in habit, the trunk not more than 10 inches thick, often branching from the ground to form three to six main stems. Some trees are erect, others spreading in habit. The foliage somewhat resembles that of A. squamosa, but the leaves are larger and of distinct form, being broadly elliptic to oblance-olate, rounded at the apex, and 4 to 5 1/2 inches in length. A distinguishing characteristic of this species is the presence of orbicular leaf-like bracts at the bases of the smaller branchlets. The flowers are maroon-colored, 1 inch long, with the three outer petals linear-oblong in form, the inner petals minute. The fruit is conical, oval, or round in form, the largest specimens weighing about 1 1/2 pounds. The surface is rough, with the carpel-lary areas indicated by deeply incised lines; from each of the areoles thus formed rises a short thick protuberance. Sometimes these protuberances are suppressed, the fruit then being almost smooth. The color varies from pale green to magenta-pink. An appearance of whiteness is given by the presence of a thick bloom over the entire surface. In the pale green varieties the flesh is white; in the pink kinds it is tinged with rose-pink. The flavor is sweet, very similar to that of the sugar-apple in the green varieties; in the pink it is more acid, resembling that of the cherimoya. The seeds are about as numerous as in the latter species but larger in size. The fruits are used fresh, like those of the sugar-apple.
Fig. 27. The ilama (Annona diversifolia), an excellent fruit from southern Mexico and Central America. (X about 1/2)
The ilama is indigenous in the mountains and foothills of southwestern Mexico, Guatemala, and Salvador, but is not known to occur at elevations greater than 2000 feet. It is found in the gardens of many Mexican and Central American towns, notably in Tapachula, Chiapas, where it is one of the principal cultivated fruit-trees. In Colima and Acapulco, Mexico, it is called ilama (the ilamatzapotl or "old women's zapote" of Hernandez), while from Tehuantepec to the Guatemalan border it is known as papauce. In Guatemala and Salvador it is named anona blanca.
The climatic requirements of the ilama are similar to those of the sugar-apple and the custard-apple. The species is found only at relatively low elevations, indicating that it prefers a hot climate. The amount of cold it will withstand has not yet been determined. The regions where it occurs most abundantly are dry during several consecutive months and subject to abundant rainfall the remainder of the year. In Guatemala it sometimes appears in places where there is little rainfall. The same is true as regards Tehuantepec, but in this region the trees are irrigated. The best soil seems to be a deep, rich, rather loose loam.
Although propagated in Mexico and Central America by seed only, the ilama can probably be budded in the same manner as other annonas. By using this method of propagation, it will be possible to perpetuate the best varieties which originate as seedlings.
The trees come into bearing when three or four years old, and sometimes produce good crops. Productive trees often bear 100 fruits in a single season. There is, however, the same variation in this regard as with other annonas, though less as to the form and size of the fruit. The ripening season is short; July and August are the principal months. When the fruits are fully mature they crack open. They are commonly left on the tree until they reach this condition but it would be better to pick them a few days earlier. So handled, they require to be kept one to three days after being taken from the tree before they soften and are ready for eating.
The ilama may be termed the cherimoya of the lowlands. The cherimoya does not succeed in the tropics unless grown at elevations of 4000 to 6000 feet, where the climate is cool. The ilama, on the other hand, belongs to the lowlands, but is strikingly similar in character to a good cherimoya. It is a valuable recruit and one which cannot be too strongly recommended for cultivation throughout the tropics.