Tamarillo (Solanum betaceum, Cav. 1799)

Identity

Tamarillo (Solanum betaceum Cav., 1799), also called tree tomato, is a shrub or small tree in the Solanaceae family, closely related to tomato and eggplant. Its epithet betaceum recalls the shape of a beet, although there is no close botanical relationship between them. ^{1 2}

The commercial name tamarillo dates to 1966, when New Zealand’s Tree Tomato Promotions Council sought a subtropical-sounding word that would be easy to pronounce in several languages. It combines a Spanish-like sound with a Māori reference to Tama-te-kapua, captain of a founding canoe. From 1966, this coined name replaced “tree tomato,” considered too close to the supermarket vegetable to market a distinct fruit. ⁴

Recognition

A single trunk with lateral branches gives Solanum betaceum its small-tree habit. It grows quickly to 3–5 m (10–16 ft), with grayish bark and brittle wood. Shallow roots leave it vulnerable to wind and drought. ^{6 3}

Broad leaves with heart-shaped bases measure 8–20 cm (3–8 in) long and release a strong, almost fetid smell when crushed. Fragrant flowers appear in clusters of 10–50, each with a pinkish-white, star-shaped corolla about 2 cm (0.8 in) across. ^{3 3 4}

Egg-shaped berries measure 4–10 cm (1.6–4 in) long. Their smooth, satin-like skin may be yellow, orange, red or almost purple, sometimes with dark stripes. The orange flesh contains many seeds and has a tart flavor reminiscent of a slightly unripe tomato, followed by a resinous aftertaste. ^{6 4}

Useful taxonomy

Kew accepts Solanum betaceum Cav. in the Solanaceae family. For more than a century the species was placed in another genus, and that older name remains common in horticultural catalogs and some databases: ¹

• Cyphomandra betacea (Cav.) Sendtn. remains the homotypic synonym most often used in current horticultural catalogs, ahead of the following two names.
• Cyphomandra crassifolia Kuntze is also a recognized synonym but has little current horticultural use.
• Solanum crassifolium Ortega completes this group of historical names recognized by Kew.

Returning tamarillo to Solanum, as confirmed by Kew and the US GRIN database, formally places it alongside tomato and eggplant, its most widely cultivated relatives. ^{1 2}

Habitat and range

Andean slopes from Colombia to Bolivia form its native range, with traditional populations in Peru and Ecuador at 1,500–3,000 m (4,900–9,800 ft). It favors subtropical rather than tropical conditions: annual temperatures of 15–20 °C (59–68 °F), rainfall of 600–4,000 mm (24–157 in) and light, deep soil. ^{3 6 4}

Commercial cultivation carried the species far beyond the Andes. New Zealand introduced it in 1891 from Indian seed, became a major producer from around 1920 and later coined “tamarillo” for export. It is also grown in Kenya, Rwanda, Ethiopia, India and China. In Victoria, Australia, garden escapes have become locally naturalized along wet temperate forest edges. ^{6 4 3}

Life cycle and reproduction

From seed, tamarillo germinates in 2–4 weeks and starts fruiting after 18 months to 2 years. Production peaks around the fourth year, while total lifespan ranges from 5–12 years, depending on climate and care. ^{4 6}

Both seeds and cuttings are used for propagation. Seedlings develop an upright trunk suited to sheltered sites; cuttings produce lower, bushier plants better suited to windy locations. Fruit ripens about 2–3 months after flowering, which may continue almost year-round in favorable climates. ^{6 3}

Uses and risks

Ripe tamarillos can be halved and eaten with a spoon, or made into juice, jam, chutney and sauces. Sweeter yellow fruit is used in Ecuadorian ceviches, while tarter red fruit is more often used in desserts. The bitter skin is rarely eaten raw. ^{4 6}

Green tamarillo parts require the same caution as those of many other Solanaceae: the skin of immature fruit and the rest of the plant contain solanine-type glycoalkaloids. Several Solanum species are too toxic for unguarded household use, warranting caution even without a dedicated entry for tamarillo itself. The ASPCA has no tamarillo-specific listing, but identifies tomato, a related nightshade with a similar toxic mechanism, as toxic to cats, dogs and horses. Precautions used for tomato foliage also apply to unripe tamarillo. ^{5 7 8}

Varieties, look-alikes and related plants

Two fruit forms dominate trade: the widespread, tarter red form and the sweeter yellow or golden form, valued in Ecuador. The regional Naga tree tomato, grown in Nagaland, India, under the local names si binyano and khwüdi, has a protected geographical indication. ⁴

The plants most often confused with tamarillo are:

• Solanum quitoense, naranjilla, another tree-like Andean Solanum with edible fruit;
• Solanum mammosum, whose inedible fruit has a vaguely similar outline;
• Solanum lycopersicum, tomato, an herbaceous relative with markedly smaller fruit.

The single woody trunk of Solanum betaceum, absent from Solanum lycopersicum, readily separates it from tomato. Smooth fruit measuring 4–10 cm (1.6–4 in) and the fetid smell of crushed foliage help distinguish it from Solanum quitoense and Solanum mammosum.

Main sources

• Plants of the World Online / Kew, Solanum betaceum Cav.
• USDA ARS GRIN Global, Solanum betaceum taxonomy record
• VicFlora / Royal Botanic Gardens Victoria, Solanum betaceum
• Wikipedia (EN), Tamarillo
• Wikipedia (FR), Tamarillo
• Purdue Center for New Crops, Morton, Fruits of Warm Climates — Tree Tomato
• NC State Extension Gardener Plant Toolbox, Solanum genus
• ASPCA, Toxic and Non-Toxic Plants — Tomato Plant