All about tomatoes

Information about our favourite vegetable... errr... fruit?

Botanically speaking, the tomato you eat is a fruit. So are watermelon, green pepper, eggplant, cucumber, and squash. A "fruit" is any fleshy material covering a seed or seeds.

Horticulturally speaking, the tomato is a vegetable plant. Most fruits, from a horticulture perspective, are grown on a woody plant (apples, cherries, raspberries, oranges); the exception is strawberries.

In 1893, the United States Supreme Court ruled that the tomato was a "vegetable" and therefore subject to import taxes. The suit was brought by a consortium of growers who wanted it declared a vegetable to protect U.S. crop development and prices.

Nomenclature and "genealogy"

The botanical name for the tomato has changed several times. Its earliest name was Lycopersicon or literally, wolf peach. Once the tomato was placed in the Solanum (Solanaceae) family, the botanical name changed to Solanum lycopersicon. Today the tomato is known as Lycopersicon esculentum, literally "edible wolf peach".

Tomatoes belong to the same family (Solanaceae) as potatoes, peppers and eggplants. Lycopersicon esculentum (tomato) is a perennial plant in the tropics but in northern climates it is grown as an annual. Flowers are generally borne in clusters of 4 to 8 but small fruited types may have 30 to 50 flowers per cluster. The flowers are mainly self pollinated by the wind. The fruit has 2 to 18 locules (chambers or sections).

The tomato is a native of the Peru, Bolivia, and Ecuador area of the Andes Mountains. Its antiquity is uncertain in regard to cultivation but it was being cultivated prior to the arrival of the Europeans. It was not until the early 19th century that the tomato was considered suitable as a food crop in the northeastern United States.


Tomato germination and growth themometerTomatoes and temperature

Tomatoes respond well to warm temperatures. The minimum temperature for seed germination is 10°C with a maximum temperature of 35°C and an optimum range of 17°C to 20°C.

Transparency master

Most field transplants should not be set out until the danger of frost is past.

An optimum growth rate is obtained at 22°C with reductions occurring above 30°C and below 12°C. Fruit setting is inhibited above 30°C and below 16°C. Rough fruit (cat faced) results from growing temperatures below 16°C.

Root growth does not occur below 16°C.

Soil and water

Tomatoes require adequate, even moisture, particularly at flowering and during fruit set.

Tomatoes grow best in well drained soils that are well supplied with organic matter. Sandy soils are suited for the speedy production of fruit. Loam and clay loam soils promote slower development.

Shelter from wind is important.

A pomato plant?

The tomato, pepper, eggplant and potato are closely related. The tomato plant is occasionally grafted to the potato, resulting in a freak plant which may produce tubers below ground (potatoes) and tomatoes above. This odd plant is sometimes called the "potomato" or "pomato".

Student Activities

The following student activities can be used as extensions of the Tomatosphere experiment. Teachers should choose activities to compliment the curriculum and needs of the students or groups of students. The activities may be adapted to individual, small group or whole class settings.

Safety note: Be aware of any student allergies. Remind students to wash their hands well after handling plants.

The tomato plant

Tomatoes are flowering plants

Plan an investigation

Discuss with students the basic requirements for the growth of green plants. Ask students to predict what would happen if any of these requirements were not met.

Divide the class into small groups. Ask each group to decide which condition of plant growth they wish to investigate (i.e. sunlight, air, water, nutrients or warmth). Discuss with students the process to follow in planning and carrying out their investigation.

Theory, prediction, experiment and observation

Distribute an Investigation Plan sheet to each group. Groups must submit their plans for approval before beginning their investigations.