Description
The plant is a small, half-woody, fast-growing, brittle tree; shallow-rooted; reaching 10ft in height.
Flowers are borne in small, loose clusters near the branch tips. Fruit size ranges from 2 to 4 inches long and 1 1/2 to 2 inches width. Skin color may be solid deep-purple, blood-red, orange or yellow, or red-and-yellow, and may have faint dark, longitudinal stripes.
Flesh color varies accordingly from orange-red or orange to yellow. While the skin is somewhat tough and unpleasant in flavor. The flesh is juicy and sub acid to sweet. The fruit has a slightly resinous aroma and the flavor suggests a mild or underripe tomato with a faintly resinous aftertaste.
Origin and Distribution
Generally believed to be native to the South Americas. In East Africa the fruit is mainly grown in Migori, Kisii, Kakamega, Meru, Murang’a, Embu, Nyeri, Nyandarua, Kericho, among others.
Varieties
Gold-mine, Solid Gold, Inca red, Rothamer Red, Red Oratia, and Ruby red.
Local preferences are based on 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. Yellow fruits are considered best for preserving because of their superior flavor.
Climate
The tamarillo prefers subtropical climate with altitude ranging from 1300m asl- 2400m asl, they grow in many parts of Kenya with rainfall between 600 and 4000 millimeters and annual temperatures between 15 and 28 °C. It is intolerant to frost (below – 2 °C) and drought stress. It is assumed that fruit set is affected by night temperatures. Tamarillo plants grow best in light, deep, fertile soils, although they are not very demanding. However, soils must be permeable since the plants are not tolerant to water-logging. They grow naturally on soils with a pH of 5 to 8.5.
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 before setting out the plantation in order to protect the young plants. Hedges of Leucena, Calliandra, Grevillea or even rows of maize can act as windbreaks.
However, those that are grafted on “Muthakwa”, bugweed, have a better root anchor that’s deeper and therefore are not easily blown over by wind. The “muthakwa” rootstock is also resistant to most soilborne pests and diseases and also provides for a better water and nutrient uptake.
Soil
The tree tomato cannot tolerate tightly compacted soil with low oxygen content. It requires fertile, light soil. 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.
Culture
The trees are set out in pits dug out at 2-3 ft square and 3 ft deep with a spacing of 4 to 5 ft (1.2-1.5 m) apart. Closer planting is recommended in windy, unprotected locations. The top soil should be kept aside and mixed with organic matter at a ratio of 1:1 while the subsoil is spread in the farm. The seedling should be planted in the middle of the hole and covered with the mixture of soil and organic matter leaving a sump that will help in water retention.
Recommended fertilizer application is 250gms of DAP per tree at planting and well mixed with the top soil/organic matter mixture. 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. After the first 2-3 months a nitrogen based fertilizer is recommended, a CAN or Urea also at 200-250gm per tree to improve on the vegetation.
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, in as much 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.
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 8 months to 1 year 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. Each tree is expected to yield (20-30 kg) of fruit annually. The fruit does not ripen simultaneously and several pickings are necessary.
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 aphids and thrips.
The principal disease is powdery mildew which may cause serious defoliation if not controlled. Minor problems include Sclerotinia disease, the black lesions of which girdle stems and cause terminal wilting; and Ascochyta disease 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.
Die-back, of unknown origin, at times is lethal to the flowers, fruit cluster, twigs and new shoots.
Abnormality: Small, hard, irregular, semi-transparent “stones” occur in the flesh of tree tomatoes and must be strained out in the process of jam-making.