Tomato (Solanum lycopersicum*)

The original tomato, in the wilderness of the highland of Peru, was a herbaceous plant (non woody, herb like);bearing small green fruit. This is rather different from our contemporary image of a tomato. What has not changed, since tomatoes were cultivated, is the word we use practically every day, especially in summer. The word tomato derives from the Nahuatl word tomatl, meaning swelling fruit.

The exact date of domestication in South America remains unclear. The Spanish spread the plant in their Caribbean colonies and cultivated tomatoes in their homeland around 1540. Tomatoes appeared in Italian literature in 1544 and was referred to as pomo d'oro or golden apple. The Italian name for tomato still is pomodoro. Indeed, the plant that was first introduced had small, yellow fruits.

Its arrival in England was, like you would expect of the weather, cold. Regrettably for our plant of interest it closely resembles deadly nightshade, a particularly toxic plant. As a gardener, I also suspect that the first tomatoes to reach Britain were acclimatised to warmer conditions and did not perform as desired under higher latitudes. Unlike the French, tomatoes did not renounce conquering Great Britain and by the mid-18th century it became a common sight on most tables. Tomatoes were introduced in the Middle East early in the 18th century. The Iranians have named it "gojeh farangi" or foreignplum.

ANATOMY AND TAXONOMY:

The tomato is a fruit, more precisely a berry. It belongs to the Solanaceae family, with deadly nightshade, potatoes and eggplants. Some species of the family Solanaceae have narcotic properties.
The word Solanum* finds its origin in the latin solamen meaning to solace or comfort and lycopersicum* literally means wolf peach. In German myth, werewolves were said to be summoned using deadly nightshade, a plant whose flowers closely resemble those of tomatoes.
Determinate bushes and vines bear their fruit all at once. This characteristic is preferred by commercial growers to keep the cost of harvest low.
Other plants are indeterminate, meaning that harvest will keep on right through to the end of their growing season. This type of plant has completed its cycle when hit by the first frost and then dies. Most heirloom varieties are indeterminate and are preferred by home growers.

SELECTION:

Around 7500 cultivars of tomatoes are available worldwide.Tomatoes come in all sorts of shapes, textures and colours: red, yellow, orange, pink, white, cream, purple, black, green, and stripped, plus everything in the middle. Wherever you may be worldwide you should be able to grow several cultivars that will suit your needs.
Tomato selection is focused on 3 different aspects: ease of cultivation, extended harvest season and culinary use. Early selections addressed practical problems and tried to produce plants that were better suited to different climates, soil types and were more resistant to pests and diseases. Since storage was not available, it became necessary to harvest for as long as necessary throughout the growing season. Plants were selected that were able to produce crops for extended periods. As the popularity of tomatoes grew, so did the need to produce plants that could fit into and compliment traditional dishes. Tomatoes are used to create delicious sauces, to eat fresh, to stir-fry, to can and more. Make sure you select varieties that are suited to your needs. Fruits only are edible, as leaves and stems are toxic if ingested.

GROWING REQUIREMENTS:

It is important not to plant a tomato crop where the previous year you grew a member of the same family or closely related (i.e. eggplants, potatoes, chillies or tomatoes). Crop rotation is essential.
Tomatoes grow well with 7 hours of sunlight per day and a soil pH between 5 and 7 (slightly acidic). Do not plant your tomatoes out when average temperatures are below 13C or over 27C, as it will impact on flowering, especially older varieties with larger fruits. If you live in a hotter climate select your varieties carefully. Ovules and pollens are destroyed when day time temperatures are over 38C and night time temperatures over 20C for 5 to 10 days.
Soil type does not seem to affect them as long as it is well drained and fertile. Once planted in its final position, leave young plants to establish for 3-4 weeks, before fertilizing with an N-P-K (nitrogen-phosphorus-potassium) ratio of 5-10-10. For initial growth, young plants need nitrogen. However, potassium encourages fruiting. It is important to obtain the right ratio, as an excess in nitrogen will cause the plant to grow more green material than fruits. Lack of calcium often causes blossom rot and bottom of fruit blackening. Some people use unwanted milk that they dilute with water and pour the mixture underneath their bush (do not water this over the foliage).
For a tomato plant to offer generous fruits for many weeks, you should fertilise your bush/vine 2 or 3 times during the growing season (more often if they are in pots). Hungry plants display symptoms such as yellow, fading leaves and black/purple tips. On the other hand, overfed plants are lush and soft but do not produce a lot of fruit. These plants will be weak, susceptible to wind damage, pests and diseases.
Stake your plants as early as you can for support and avoid the breaking of branches. Tomatoes can be grown in containers, the bigger the better to give plenty of room to the roots. A good rule of thumb is to select plants with smaller fruits. Use quality potting mix, fertilize and water your plants often.
To prune or not to prune? Here is a question heavily debated by horticulturists, gardeners and producers. For some, pruning is essential, others are strongly against, while a minority of tomato lovers have positioned themselves somewhere in the middle. We advise you to do whatever works for you. However, all agree on the fact that determinate plants should not be pruned.
The quality of your crop relies on your watering regime. Tomatoes need regular and thorough watering at the base of the plant, not on the foliage.

PESTS AND DISEASES:

The golden rule with all fruits and vegetables is the healthier they are the less susceptible they will be to pests and diseases. Adopt a proactive approach and ensure that your soil, watering and fertilizing regime is right.When attacked by insects, a healthy tomato plant produces molecules which slow the growth of insects.
The most common tomato pests are aphids, white flies, Colorado potato beetle, red spider mites and slugs.
Mildew and blight are the most common diseases encountered when growing tomatoes. They can be lethal at seedling stage, so always offer your little ones a good aeration and disinfect propagation units before re-use. Tobacco mosaic virus has to be mentioned, as it is contagious. Do not place infected plant material in your compost. Infected leaves appear discoloured: yellowish and/or with pronounced veins.

COMPANION PLANTS:

Tomatoes should not be planted next to rosemary, potatoes and fennel. However, carrots, parsley, coriander and parsnips (Apiaceae family) constitute good companions, as they attract beneficial insects, such as parasitic wasps and predatory flies.
Other families such as alliums (garlic, chive and onion) and mints (basil, oregano and spear mint) cover the smell of tomatoes, making it difficult for insects to locate the plant. They may also enhance the flavour of tomatoes, try basil!!
Asparagus and tomato mutually benefit from one another. Asparagus repels tomato root nematodes and tomatoes are toxic to asparagus beetles.

HARVEST:

Tomatoes can be harvested before they are ripe and placed on a window sill. Adopt this technique, if you suffer from possum, rat, bird or fruit fly attacks.
The flavour of tomatoes deteriorates when they are placed in a fridge.
To obtain a regular supply of fresh tomatoes, select varieties with harvest seasons that do not overlap. By doing so, you will be picking fruits all through the growing season.
If you end-up harvesting more than you can handle make sauce, freeze them, can them or simply share them with your neighbourhood.

SEED COLLECTION:

If you have been hooked by a particular variety and want to collect seeds, make sure you select the best fruits and that they are free from pests and diseases. Seeds must be disinfected, as many pathogens can spread from the parent plant to the seedling.
Two methods are available:
-Place seeds with pulp in a glass and let it ferment for a week at room temperature (4 days if temperatures are between 25C to 28C). It will result in the growth of beneficial fungi that will eliminate many pathogens that are on the surface of the seeds. Once the treatment is over wash the seeds and dry them before placing them in an envelope.
-Remove the pulp and dip seeds in a 1% hydrochloric acid solution for 24h, then rinse, dry and store.

Neither treatment eliminates viruses or bacteria.

SUMMARY

WHY grow your own tomatoes?
Commercial growers do not make money because their tomatoes have a great flavour. They breed tomatoes for the consistency of their size and shape, which facilitate mechanized picking and shipping, pests and diseases resistance and their ability to mature after picking. So try to grow heirloom varieties to discover new flavours. Furthermore, why bother growing varieties of tomatoes that are readily available at your local supermarket? Health wise, tomatoes are made of 93 to 95% water, have virtually no calories (18 to 20 kcal per 100 grams) and are rich in vitamins A, C, E and potassium.

WHAT are tomatoes?
Tomatoes are from South America and belong to the Solanaceae family. Botanically, they are a fruit.

WHEN can you grow tomatoes?
As soon as the risk of frost is over you can plant tomatoes out. From seedling stage to your first tomato, it will take around 2 to 3 months.

HOW can you grow tomatoes?
When the time comes to transplant your tomatoes, bury the stem up to the first leaves to give your plants better anchorage. Do not plant them too close. Observe a strict watering regime, which is the key to a successful, healthy tomato crop. Fertilize with an NPK ration of 5-10-10. If you live in a cooler climate, do not mulch too early to give the soil time to warm up. Once the weather gets hot, mulch promptly. The most common tomato pests are aphids, white flies, slugs, red spider mites and Colorado potato beetles. Blight, mildew and potato mosaic virus are the most common diseases.

WHERE can you grow tomatoes?
Anywhere, as long as it is a sunny and warm spot, getting at least 7hours of sunlight a day and in a fertile soil. They grow best with day temperatures below 27C and above 13C. Day temperatures above 38C, even for a few days, can prevent flowering.

(*Should have been in italics)

Aurélie Quade