Josephat Chengole Mulindo
Introduction
You can never go wrong with tamarillo (tree tomato) production. It is an easy plant to propagate, the cost of its seed is affordable and the fruits are highly marketable locally and in the export market. This is because tree tomatoes are known for their nutritional and health benefits.
The tamarillo was originally a yellow and purple coloured fruit. However, in the 1920’s, a red-skin variety was developed and is now the most commonly known variety of the fruit. Others still exist and are common among Kenyan farmers – yellow, orange, deep purple and dark stripped. This rainbow fruit has its colours associated with taste. The red fruits are more acidic while the yellow and orange fruits are more sugary-sweet.
Tamarillo plant is a small sized tree reaching about 100 to 400 centimetres in height with hairy stems and branches. It has a shallow fibrous rooting system. The leaves are large, simple and perennial with a strong pungent smell. A mature tree bears pink-white flowers that come in clusters of 10 to 50 floral pieces. They produce one to six fruits per cluster. The fruits are generally egg-shaped measuring 4 – 10 centimetres long. The plant has a lifespan of up to 12 years.
Ecological requirements for tamarillo (tree tomato)
Tamarillo is a subtropical plant. It does well in areas with warm conditions that are not affected by strong winds. Specifically, the plant requires the following ecological conditions;
Soils: Tamarillo trees require well-drained fertile soils, rich in organic matter. They grow naturally on soils with a pH of 5-8.5. Perfect drainage is a must and the trees do not tolerate waterlogging.
Climate: Tamarillo requires rainfall ranging between 600-4000 millimetres and annual temperatures between 150C and 25°C. The plant is intolerant to frost (below -20C) and drought (below 300 mm of rainfall per year) stresses.
Altitude: In Kenya, tamarillo grows well in altitudes between 1,500m to 3,000m above sea level.
Propagation
Tamarillo can be propagated by seeds, cuttings or grafted seedlings. Seeds produce a high-branched, erect tree, ideal for sheltered locations.
To ensure the outcome from seed propagation breeds, one should be careful to take seed from red fruits with black seed pulp or yellow fruits with yellow seed pulp. Cuttings develop into shorter, bushy plants with low-lying branches that are suited for open spaces where winds may be a challenge.
Cuttings are obtained from healthy pruned wood from a mother plant that is about 12 months old then trimmed to about 12 inches long.
Grafted seedlings are obtained from a bug weed rootstock and a tamarillo scion of a desired variety. The bug weed has a taproot system while the tamarillo has the fibrous shallow rooting system.
Nursery establishment
Though seeds can be sown directly in the farm, it is better to start them in a nursery to ensure you have robust seedlings to begin the tamarillo orchard with.
Variety selection: Varieties to propagate should be selected depending on market requirements. Red fruit variety has an appealing colour and is more preferred in the Kenyan market.
Seed extraction: Seeds should be extracted from mature fruits harvested from vigorous and heavy fruit bearing and healthy trees to prevent seed borne diseases. The fruits are washed then cut in two pieces. Seeds are scooped out and washed to remove the sticky material. The seeds are then dried in direct sunlight for about 7 days. The dried seed is viable for 3 months.
Nursery preparation: Ideal site for the nursery should be under the sun and should not have had other crops like managu, Irish potatoes, pepper, tobacco and eggplant in the past 4 seasons. The nursery soil should be well aerated, drained and with good pH. Ploughing should be done to a depth of 20-30 centimetres and stones, weeds and debris removed. Well decomposed organic manure (5 kg/m2) should be mixed with the nursery top soil, one week before planting. The nursery bed should be above ground level with a length of 100 centimetres and a width of 20 centimetres.
Sowing seed: For an acre, 2.5 grams of viable seed is required (an equivalent of about 1200 seedlings). The bed surface should be levelled and sowing lines of 0.5 centimetres depth are made using a stick. Seeds are sown in lines at the spacing of 20cm x 5cm and are covered with little soil. Apply mulch on the bed, followed by regular watering. Between 7 and 10 days later, the seeds should have germinated. Remove the mulch and create a raised overhead shade to protect the seedlings from direct sunlight and heavy rain intensity. One month later, when seedlings are 5 centimetres in height, transfer them to polytubes or pots that are 13 centimetres in diameter. The seedlings will be ready for transplanting in about 3 months. One to two weeks before transplanting, harden up the seedlings by reducing the irrigation frequency and exposing the seedlings to greater sunlight intensity.
Transplanting tamarillo (tree tomato)
Land for tamarillo production should be located in a place with an adequate supply of water. Tamarillo requires adequate watering at least once a week. Make provision for a water tank on the farm if rain water is inadequate.
Land preparation should start at the time the nursery is established. The field has to be ploughed at a depth of about 20-30 centimetres, the debris removed and then levelled.
Dig holes of 60cm × 60cm × 60cm. Separate topsoil from subsoil. Discard subsoil. Mix topsoil with a bucket of fully decomposed farmyard manure and fill the hole. If it is dry, water the mixture in the hole before transplanting your seedling. Plant the seedling to the depth it was in the polytube. Put mulch around the hole and ensure moist and not waterlogged soil conditions.
Field management
Mulching: Select good organic material as mulch. If material is adequate, cover the whole field. If inadequate, cover the area around the planting hole. Mulching prevents loss of soil moisture, controls weeds by shading them and diseases by preventing soil contact with the plant foliage. It controls soil temperature by keeping it cool or keeping it warm and adds to soil fertility when organic mulch decomposes.
Weeding: The tamarillo field should be kept weed-free. Weeds compete for nutrients and space with the fruit trees. Besides, they act as hosts for pests, fungi and viruses that may affect the tamarillo plants. While doing manual or mechanical weeding, the shallow rooting system of tamarillo trees should be considered.
Pruning: At a height of about 100 centimetres the top of the plant should be chopped off to encourage branching and keep the height of the crop to a manageable level for ease of harvesting. Plants grown from cuttings generally grow with many low branches. These should be removed so the plant branches are far enough above ground level to prevent infections.
Irrigation: Tamarillo plants are sensitive to drought. Lack of water limits plant growth, fruit size and yields.Tamarillo plants need irrigation during dry periods and peak growth times.Drip irrigation is most preferred for delivering water directly to the roots whilst leaving foliage and fruits dry, to minimize infections. However, the choice of method of irrigation will depend on your local economic and land physical realities.
Use of grafted tamarillo plants reduces the plant’s vulnerability to water stress. The bug weed that is used as the rootstock has a taproot system that goes deeper in the soil to scavenge for water in the lower soil strata.
Pest and disease management: Tamarillo is fairly resistant to most diseases and pests. However, organic sprays can be used to manage blight and powdery mildew in cases of an outbreak. Whiteflies and aphids are managed by directing smoke from burning neem tree leaves into the orchard. As a general rule, avoid plant overcrowding by sticking to the recommended plant spacing. Maintain field hygiene and practise crop rotation. Use of grafted seedlings gives a boost to the tamarillo plants in pest and disease tolerance. The bug weed which acts as the rootstock is tolerant to viral infections and nematodes.
Harvesting
Tamarillos start producing fruits at 10 – 12 months of age. Tamarillo is best harvested when quite ripe, as close to complete maturity as possible. If not yet mature, it doesn’t taste good. If too young it even becomes difficult to digest. Flavour improves if the fruit is left to ripen on the tree. When the fruits develop the red or yellow colour, then they are ready to harvest. Harvesting is done by pulling the fruits from the shrubs with a snapping sound to ensure the stalk remains attached on the fruit. A single tree yields about 30 kilograms of fruit annually.
Post-harvest handling
After harvesting, the fruits should be washed to remove dust and other debris. They are then dried and sorted into batches according to size, colour and skin condition. The fruits should be packaged based on the requirements of the client.
Economics of tamarillo production
Returns: An acre of land can carry about 1,200 tamarillo trees. With each tree producing 30 kilograms, the yield per year would be 36,000 kilograms of fruit. At a price of ksh80 per kg, this results in a gross revenue of ksh2,880,000 per year.
In subsequent years, production per acre comes down to an average of 25 kilograms per tree annually yielding 30,000 kilograms with an annual income of ksh2,400,000.
The production costs in the first year are indicated in the table below.
| Item/activity | Seedlings (number) | Manure (buckets) | Holes (labour) | Weeding/pruning labour (months) |
| Quantity | 1200 | 1200 | 1200 | 12 |
| Price | 100 | 20 | 50 | 7000 |
| Cost | 120000 | 24000 | 60000 | 84000 |
Production cost in the first year will be ksh288,000. In subsequent years, the production costs are estimated at ksh84,000 annually. The net income stream is indicated in the table below up to year 5 when the orchard should ideally be replaced with a new one.
| Period | Year 1 | Years 2 | Year 3 | Year 4 | Year 5 |
| Gross income | 2,880,000 | 2,400,000 | 2,400,000 | 2,400,000 | 2,400,000 |
| Cost | 288,000 | 84,000 | 84,000 | 84,000 | 84,000 |
| Net income | 2,592,000 | 2,316,000 | 2,316,000 | 2,316,000 | 2,316,000 |
In conclusion, it can be inferred that tamarillo production is viable and very profitable.