Solanum fragrans Hook.

Cyphomandra betacea is a semi-woody shrub or small tree 2-3 m high, rarely 5 m. It is unarmed, pubescent, with a short trunk and stout lateral branches. The bark is grey. Leaves alternate, simple, entire, usually grouped at the branch tips, with a robust petiole, 4-8 cm long. The limb is large, 15-30 x 10-20 cm, ovate, shortly acuminate, with a cordate base. Young leaves covered on both surfaces with a soft pubescence; with age, the upper surface becomes glabrous. Midrib and principal veins prominent on both surfaces. Flowers fleshy pink, in groups of 3-10 in axillary cymes or racemes, near the ends of the branches. They are hermaphroditic, pentamerous, fragrant, pedicellate, 13-15 mm diameter. Calyx campanulate with broadly ovate, subacute lobes, which are thick and accrescent in fruit. Corolla rotate-campanulate, 12 mm long, with 5 long, narrow, lanceolate segments; reflexed at the apex. Stamens 5, yellow, inserted at the throat of the corolla. Fruit an ovoid berry, measuring 4-6 (max. 10) cm long and 3-5 cm wide. It is suspended at the end of a long stalk, and surrounded at the base by the persistent green calyx. Skin is thin, glabrous, smooth, reddish-brown to violet changing to orange-red at maturity. Some varieties become deep purple at maturity. Pulp contains numerous small seeds that are circular, flat, thin and hard.

C. betacea is the only member of its genus known to be self-compatible. Flowers are self-pollinating; wind and insects assist in pollen transfer, resulting in better fruit set. Fruit ripens over a period of many months. Pruning may induce flowering; once it begins, maximum fruit production lasts only 4-5 years, for a period of 5 months per year. Fruit production begins 1-2 years after sowing and lasts for 8-12 years.

Grow best on well drained soils rich in organic matter and ample moisture. They cannot withstand waterlogging even for a period of a few days.

A native of the forests of the Andes of Peru and Argentina, C. betacea has been successfully cultivated throughout the tropics. C. betacea thrives at elevations of 1000 m and more; it does well even above 2000 m if the mean monthly temperature remains above 10 deg. C and if frosts - which kill young plants - are exceptional. At low elevations, the trees do not flower; cool weather (probably cool nights in particular) promotes bloom. That is why the crop ripens in the winter in the subtropics. Flavour develops better under warm sunny days and cool nights of the dry season in the tropics than during the winter at higher latitudes. It is presently found in hilly country throughout the tropics. With a shallow root system, it has little ability to withstand drought and is easily blown over. The shallow roots and large, soft leaves of C. betacea make it particularly susceptible to wind damage. They are apparently intolerant to constant high temperatures and often their fruits fail to mature in lowland tropical climates owing to excessive heat.

C. betacea is believed to have originated in the Peruvian Andes. Beyond this, little of the origin or true domestication of the tree is known. The plant has been extensively cultivated in the Andes region, although not in large plantations, and has been grown in New Zealand, where it has had an established commercial market status since the 1890s. It has been introduced in most tropical highlands, where it is often naturalized, in the subtropics and also in some mild temperate areas. The name ‘tamarillo’, chosen over ‘tree tomato’ by New Zealanders in 1967 to avoid confusion with the garden tomato, is the name most widely accepted in commerce.

Seeds should be selected from true to type plants. In Brazil, the seeds are washed, dried in the shade and placed in a freezer for 24 hours. Chilling is claimed to result in virtually 100% germination within 4-6 days. Seedbeds should be prepared with manure or compost and lightly shaded. Propagation from cuttings is an alternative, but it is difficult to ensure freedom from virus infections. Container growing can cut planting-out losses. Cuttings of 1- to 2-year-old wood 10-30 cm thick and 45-100 cm long can be defoliated and planted directly in the field. In New Zealand, tamarillo is sometimes grafted on related species, in particular Solanum mauritianum, a naturalized weed. Trees on the stock are slightly dwarfed, but they bear prolifically and need to be staked. Fruit will keep up to 12 weeks at 3.5-4.5 deg. C with a 7-day shelflife afterwards.

Cyphomandra betacea is a fast-growing tree on good sites. Cuttings give low-branched bushy trees, which may need to be deblossomed to promote growth in the 1st year. Seedlings do not always come true to type. They grow vigorously and may reach a height of 1.5-1.8 m before laterals emerge. The plants grow continuously and easily shed old leaves. In New Zealand, trees are planted in single or double rows, e.g. at 2.5 x 2 m or 4.5 x 1.5 m against (3.5 + 1.5) m x 2 m or (4 + 2.5) m x 3 m, giving densities of 2000-1000 plants/ha. Much higher densities are reported from other countries. Orchards need to be well drained; often the trees are planted on hills or ridges. Because of the shallow root system, deep cultivation should be avoided, but mulching is very beneficial. Young seedlings are cut back to a height of about 1 m to encourage branching, and each year the plants are pruned at the beginning of the crop cycle. This annual pruning consists of cutting back and thinning out the branches that have fruited to rejuvenate the bearing wood and to limit tree spread. Time of pruning influences harvest time. Coppicing can be practised. The brittle branches are prone to break when loaded with fruit; thus sheltered locations should be chosen or windbreaks must be provided. Plants respond well to nitrogen fertilizer, particularly after the 1st fruit has set. In the tropics, using a generous amount of organic matter and manure when making hills for planting minimizes the need for additional fertilizer. Irrigation during the dry season is important to sustain growth and to improve fruit size and yield. Yields per tree average around 20 kg of fruit/year, and commercial yields are about 15-17 t/ha. Trees are short-lived; 12 years is the highest recorded lifespan of an orchard.

A major insect pest is the tree tomato worm, the larva of the pyraustid moth Neoleucinodes elegantalis. The larvae bore into the fruit, causing it to spoil prematurely and bringing on fruit losses of 40-80%. Chemical and possibly biological controls may be helpful in controlling or eliminating this pest. Aphids are one of the more common pests; they transmit cucumber mosaic virus and potato virus ‘Y’. Cucumber mosaic virus causes stunting and mottling of leaves. Potato virus ‘Y’ causes mottling of leaves and dark spots on the fruit; yield is also reduced. Phytophthora blights (P. palmivora and P. infestans) also affect plants, particularly during the rainy season. These blights can be prevented by applying copper, daconil, or maneb sprays. Principle fungal diseases include anthracnose, which hardens and deforms the skin of the fruit, and powdery mildew (Oidium spp.), an ashy-white fungus found on the upper and lower leaf surfaces of plants in Colombia and New Zealand. C. betacea may also be susceptible to verticillium wilt, a soil-borne fungus that infects tomato, potato and eggplant.

Orthodox storage behaviour; no loss in viability after 42 months of hermetic storage at -20 deg. C with 5.5% mc. Reduction in viability occurs after 8-10 months of storage at room temperature. There are about 100 000 seeds/kg.

Ornamental: C. betacea is frequently grown as a curiosity in gardens in the temperate regions of North America. It is a common sight in homegardens of Latin America. Intercropping: The species can be grown with crops such as coffee. Green manure or cover crops of grass and clover can be grown between rows. New Zealand growers often plant C. betacea as an intercrop in young citrus orchards.

Food: Tamarillos are eaten by scooping out the entire fruit, discarding the exocarp and outer layer of the mesocarp. The refreshing, raw pulp is juicy, subacidic, pink, salmon or yellow. The unripe fruit can be used for chutney, curry and sambal (hot, chilli-based condiment). Only mature, tree-ripened fruits grown under favourable conditions develop the full flavour and aroma. The rather sharp, tart flavour typical of most red cultivars can be reduced by stewing. Properly ripened fruit is also essential for good quality stews, stuffings, jellies, jams, desserts and ice cream toppings. The red cultivars cannot be canned, as the redness signifies the presence of acidity that will corrode tin cans. The hard seeds may be strained out after boiling. Lime juice and sugar can be added to taste. Halves may be seasoned and baked or grilled. The fruits of C. betacea are relatively nutritious because of their high vitamin content. They are rich in beta-carotene, making them good sources of pro-vitamin A, and they contain large amounts of ascorbic acid or vitamin C. Their high protein content makes them especially suitable for jam- and jelly-making. Levels of nitrogen and free amino acids are higher than those of most fruits except avocados and bananas; the values for potassium and phosphorus are also high among fruits, which are normally poor sources of these elements. Tannin or dyestuff: The leaves of the tamarillo have been employed as a dye. The unripe fruits are used in the Colombian tanning industry to decolour hides. Medicine: Warmed leaves are wrapped around the neck as a remedy for sore throat in Ecuador. The fruit pulp, after having been cooked in embers, is used as a poultice for inflamed tonsils in Colombia. The species was known as ‘vegetable mercury’ in Jamaica because of its presumed therapeutic value to the liver.