There are apparently no named cultivars, but there are local preferences according to fruit color. Red fruits are chosen for the fresh fruit markets because of their appealing color. The dark-red strain (called "black") now leading in commercial plantings in New Zealand was obtained by selection around 1920 as a variation from the yellow and purple types grown up to that time. It was propagated and reselection thereafter resulted in this large, higher quality, red variety.

Yellow fruits are considered best for preserving because of their superior flavor.

Climate

The tree tomato is not tropical but subtropical. It flourishes between 5,000 and 10,000 ft (1,525-3,050 m) in Ecuador; between 1,000 and 3,000 ft (305-915 m) in Puerto Rico; 1,000 to 7,500 ft (305-2,288 m) in India. In Haiti it grows and fruits to perfection at 6,000 ft (1,830 m). In cooler climates, it succeeds at lower elevations. It does best where the temperature remains above 50º F (10º C). Frost at 28º F (-2.2º C) kills the small branches and foliage of mature trees but not the largest branches and main stem. The tree will recover if such frosts are not prolonged or frequent. However, seedlings and cuttings are readily killed by frost during their first year.

Protection from wind is necessary as the tree is shallow-rooted and easily blown over. It is also brittle and its branches are easily broken by gusts, especially when laden with fruit. It is suggested that windbreaks be established for each 1/2 acre (1/5 ha) before setting out the plantation in order to protect the young plants. Hedges of Albizia lophantha Benth. and of Hakea saligna R. Br., kept trimmed and narrow, are popular in the North Auckland area of New Zealand.

Soil

The tree tomato cannot tolerate tightly compacted soil with low oxygen content. It requires fertile, light soil. It grows well on deep lateritic soil in Haiti. Perfect drainage is necessary. Water standing for even a few days may kill the tree.

Propagation

Seeds or cuttings may be used for propagation. Seeds produce a high-branched, erect tree, ideal for sheltered locations. Cuttings develop into a shorter, bushy plant with low-lying branches, suitable for exposed, windy sites. The tree does not always come true from seed, but is most likely to if one is careful to take seed from red fruits with black seed pulp or yellow fruits with yellow seed pulp.

In Brazil, seeds for planting are first washed, dried in the shade, and then placed in a freezer for 24 hours to accelerate germination. They are then planted in boxes of rich soil–12 in (30 cm) between plants and 24 in (60 cm) between rows–and virtually 100% will germinate in 4 to 6 days.

Culture

The seedlings are set out in the field when 2 to 2 3/4 in (5-7 cm) high, spaced 32 in (80 cm) apart in rows 6 1/2 ft (2 m) apart. In New Zealand, the trees are set 8 to 10 ft (2.5-3 m) apart in paired rows 8 ft (2.5 m) apart with 14 ft (4.25 m) between each pair. If the soil is very rich, 9 ft (2.75 m) is allowed between the rows and 16 ft (5 m) between the pairs. Closer planting is recommended in windy, unprotected locations–5 to 6 ft (1.5-1.8 m) between the plants and 8 to 10 ft (2.5-3 m) between the rows, and the trees may be staked to prevent swaying and disturbing the roots. In India, the trees are set out in pits 4 to 5 ft (1.2-1.5 m) apart.

Cuttings should be of 1- to 2-year-old wood 3/8 to 1 in (10-25 mm) thick and 18 to 30 in (45-75 cm) long; the leaves are removed and the base cut square below a node. They can be planted directly in the field and, while precocious, should not be permitted to fruit in the first year.

Recommended fertilizer application is 0.5 to 2.2 lbs (0.25-1.0 kg) per tree of NPK 5:6:6, half in early spring and half in midsummer. In the 5th or 6th year, the grower is advised to give a special feeding of 2 parts superphosphate, 1 1/2 parts nitrate of soda, 1 part sulphite of potash, in late winter or early spring, at the rate of 2 to 3 lbs (1-1.5 kg) per plant–approximately 10 to 16 cwt per acre, or 100 kg per hectare.

Because of the shallow root system, deep cultivation is not possible, but light cultivation is desirable to eliminate weeds until there is sufficient vegetative growth to shade them out.

Seedling trees are pruned back the first year after planting to a height of 3 or 4 ft (0.9-1.2 m) to encourage branching. Annual pruning thereafter is advisable to eliminate branches that have already fruited and induce ample new shoots close to the main branches, inasmuch as fruit is produced on new growth. Otherwise, the tree will develop a broad top with fruits only on the outer fringe. And wide-spreading branches are subject to wind damage. Pruning facilitates harvesting and, if timed appropriately, can extend the total fruiting period. Early spring pruning of some of the owners' trees brings about early maturity; fall pruning of other trees delays fruit maturity to the following fall.

Irrigation

The tree tomato cannot tolerate prolonged drought and must have an ample water supply during extremely dry periods. A mulch is very beneficial in conserving moisture at such times.

Pollination

Tree tomato flowers are normally self-pollinating. If wind is completely cut off so as not to stir the branches, this may adversely affect pollination unless there are bees to transfer the pollen. Unpollinated flowers will drop prematurely.

Cropping and Yield

The tree usually begins to bear when 1 1/2 to 2 years old and continues to be productive for 5 or 6 years. If then adequately nourished, it may keep on fruiting for 11 to 12 years. In Brazil, each tree is expected to yield 44 to 66 lbs (20-30 kg) of fruit annually.

The crop does not ripen simultaneously and several pickings are necessary. The fruits are clipped, leaving about 1/2 in (12.5 cm) of stem attached. They are collected in bags worn by the harvesters.

In New Zealand, the fruits are sorted by size–small, medium and large–and packed in paper-lined wooden boxes for marketing. Because of its firm flesh and tough skin, the fruit can be shipped long distances without bruising. However, it deteriorates rather rapidly under ordinary storage conditions.

Pests and Diseases

The tree tomato is generally regarded as fairly pest-resistant. A looper caterpillar makes large holes in the leaves of young plants in the nursery but causes little damage to trees in the field. Occasionally the plants are attacked by the green aphis.

In South America and the Caribbean, the fruits are subject to attack by fruit flies–Anastrepha sp. and Carpolonchaea pendula (syn. Silba pendula). In Colombia, the tree tomato has been found to be the preferred host of the tree tomato worm (Neoleucinodes sp.) which infests also the tomato and the eggplant. The larvae feed on the fruits and cause heavy losses. Rigorous spraying and sanitary measures are required to reduce losses and means of biological control are being sought.

The principal disease is powdery mildew (both Erysiphe sp. and Oidium sp.), which may cause serious defoliation if not controlled. Minor problems include Sclerotinia disease (Sclerotinia sclerotiorum), the black lesions of which girdle stems and cause terminal wilting; and Ascochyta disease (Ascochyta sp.) which is evidenced by small, round, black, dead areas on leaves, especially mature leaves. Tree tomato mosaic virus causes pale mottling on leaves and sometimes on the fruits which has not been considered a serious disadvantage. Another virus disorder, called "bootlace virus", distorts the leaf, especially on young plants, reducing it to little more than the midrib. Affected plants are pulled up and destroyed.

The tree tomato is noted for its resistance to tobacco mosaic virus, though it is susceptible to cucumber mosaic virus and potato virus. Die-back, of unknown origin, at times is lethal to the flowers, fruit cluster, twigs and new shoots. A strain of Arabis mosaic virus (which, in combination with two other unidentified viruses, causes sunken necrotic rings on the fruit surface) was reported in two plantations in the TePuke-Tauranga area of New Zealand in 1971, together with the identification of its vector, the nematode Xiphinema diversicaudatum.

Abnormality: In Haiti and New Zealand, small, hard, irregular, semi-transparent "stones" occur in the flesh of tree tomatoes and must be strained out in the process of jam-making. It is not known if these are similar to the "two gritty lumps in the wall of the fruit (on opposite sides)" mentioned by E.J.H. Corner as observed in Malaya. Samples of the stones were examined at the Division of Plant Industry, Florida State Department of Agriculture, and were found to contain "large amounts of sodium and calcium, probably as silicates, borates, aluminum-magnesium-oxygen complexes, or aluminates or magnesium oxides. In addition, small amounts of tin, copper, chromium, iron and phosphorus were found. " It is well known that plants may accumulate minerals from mineral-rich soils, but such stony accretions are found in the leaves, not in the fruits. At Tela, Honduras, concretions occur in mangosteens, often rendering the fruit inedible. The cause has not been determined.