Tomatoes (Solanum lycopersicum) belong to the nightshade family (Solanaceae) and originate from Central and South America. For the indigenous natives of Latin America, fruit vegetables were an integral part of their diet. The first tomatoes came to Europe as early as the 16th century, where they were first cultivated primarily as ornamental plants. More productive varieties were not bred until the beginning of the 20th century. From then on, tomatoes also became established in our fields as fruit vegetables. Today they are cultivated in almost all countries of the world – and loved by hobby and professional gardeners alike.
Appearance and growth
Tomatoes are annual and grow between 20 inches (bush tomatoes) and two feet (bar tomatoes) high. Its dark green and fleshy leaves are coarsely pinnate and slightly hairy. The spicy scent of the tomato plants is unique. From May, up to 20 small, yellow flowers appear in the leaf axils, which pollinate themselves. Within two months, green berry fruits develop, which then turn red, yellow or blackish depending on the variety. In the meantime, even green tomato varieties are available on the market and tomatoes are generally distinguished according to their growth and fruit shape:
Tree tomatoes (long main shoot that must be tied open),
Bush or balcony tomatoes (bushy growth and limited height growth),
beef tomatoes (very large, ribbed fruits with five to ten chambers) and
Cherry or cocktail tomatoes (small, cherry or pear-shaped fruits).
Location and soil
Tomatoes thrive on well loosened soils rich in humus and nutrients. Three to five litres of compost per square metre – spread after soil preparation – ensure the basic supply of nutrients and improve the humus content of the soil. The plants react sensitively to heavy soils in which waterlogging can easily occur. The location is a sunny, warm and wind-protected place.
There are different cultivation variants: Tomatoes thrive in tubs and pots, in greenhouses and outdoors. Cultivation in pots is possible with small balcony varieties such as ‘Miniboy’, which grow to just half a metre in height. The pots and pails should have a capacity of at least ten litres. Make sure that the water can drain off well. The cultivation under a tomato house open to the sides is particularly recommended, where temperatures never rise above 35 degrees Celsius even in midsummer. There the plants can be guided up by strings or rods.
Tomato houses are available in many sizes in specialist shops. With a little skill you can simply build the house yourself from wooden slats and UV-resistant greenhouse foil. Important: The open side must face away from the weather side, i.e. must not point west in our latitudes in the United States. All-round closed houses or special tomato hoods for outdoor use are not recommended as permanent rain protection: At changing temperatures, condensation water forms under the film and infestation with fungal diseases is favoured. For this reason, tomatoes should also be aired daily in the greenhouse.
Crop rotation and mixed cultivation
Tomatoes are the most important strong eaters in crop rotation. They should be placed in a new bed every year. If the plants are always in the same place, soil pests such as small roots and the pathogens of the cork root disease can multiply strongly. Along the rows, low and warm herbs such as basil can be placed. Tomatoes are also good neighbours for other plants: It is believed that the smell of the tomato leaves dispels pests. Carrots, radishes, spinach or cabbage thrive in their vicinity. However, potatoes, peas and fennel are not recommended as neighbours. Especially potatoes should be avoided at all costs, as the fungal pathogen of the dreaded potato disease brown rot hibernates in them and infects the tomato plants in spring.
Anyone who deals with the sowing of tomatoes will have encountered the terms “organic seed” or “F1” on the seed packets more often than not. Behind this lies the way in which the seeds were produced – and this is a very important point, especially for self-sufficient people. Organic seeds are so-called seedsolid seeds. The parent plants were traditionally selected by selection over decades or even centuries. If the seed is picked up from the harvested fruit and sown again next year, tomatoes with the same characteristics are obtained again, provided that the plants have not crossed with other varieties.F1 seed, on the other hand, is obtained by seed breeders by means of a rather complex hybridisation process. The desired properties of the mother plants can be specifically recombined by crossing them in the so-called F1 generation – the offspring. The seed obtained from the crossed parent species – the so-called F1 generation – is sold and is particularly efficient. However, the plants are not inherited: if their seeds are collected and sown again, the characteristics of the F2 generation deviate greatly from those of the F1 generation.
It is not only organic gardeners who are critical of the widespread use of F1 seed, because it is ultimately a lucrative business for seed manufacturers because growers and farmers have to buy new seed every year and cannot multiply it themselves. It also leads to the loss of more and more old traditional seed varieties, which is a major problem in many developing countries, for example. There is no reason why F1 seed should not be used for one’s own needs, but in many cases old tomato varieties are just as robust, tasty and high-yielding. In addition, you can no longer buy seedproof varieties only from specialised suppliers – organic tomato seed, such as the ‘Ochsenherz’ variety, is also available in classic garden specialist shops. Whatever seed you use: Tomatoes are best sown and pre-cultivated under glass. You should take care not to sow too early. The period from the end of March to the beginning of April is the best. Then tomato seeds can be sown thinly in single pots or seed trays and kept very light and moist at 18 to 20 degrees Celsius. This succeeds on a bright windowsill or in a heatable small greenhouse. Eight to ten days after sowing, the seeds begin to germinate.
After about three weeks, as soon as the seedlings have developed the first two pairs of leaves, they are individually pricked into pots about ten centimetres in size. Water the young plants constantly and only put in a short drying phase shortly before planting out, in order to give an impulse for root growth.
If you haven’t preferred your tomatoes yourself, you can buy seedlings of all common varieties from the spring in the garden centre or order them from mail-order nurseries. More unusual varieties are usually only offered as seeds. Pre-grown young plants of many varieties are now also available in grafted form. The advantage: The plants grafted onto a strongly growing wild tomato deliver up to 60 percent more fruit and are particularly suitable for cultivation on balconies, terraces or in greenhouses. The only disadvantage is that the fruit tends to burst, so the plants depend on an even supply of water and nutrients. As tomatoes do not tolerate frost, you should wait until the ice saints have passed before planting them out. In an unheated greenhouse, an earlier planting date is of course no problem. If you want to harvest early without a greenhouse, you can plant the seedlings outdoors in mild locations as early as the end of April and cover them with a foil hood if there is a risk of night frost. Remove the cover again in the morning and make sure that the foil hood has spacer rings and air holes. Avoid contact between leaves and foil as this increases the risk of fungal infection.
Tomatoes are strong eaters: you should fertilise the bed with compost and manure before planting and work this well into the soil. A wide planting distance of at least 50 x 60 centimetres ensures aeration. Water the tomatoes vigorously immediately after planting. In the following days, the young plants should not receive any water so that root growth is stimulated again. To ensure that the tomato plants have a better footing, plant them down to the lowest leaf base so that the root base is five to ten centimetres covered with soil. As a result, the plants form additional fine roots on the lower part of the stem and can absorb more nutrients. With grafted tomatoes, the ball of the pot should just be visible!
With the exception of bush tomatoes, all tomatoes need a climbing aid. Spiral bars made of stainless steel or aluminium are practical and easy to clean. Disinfect the sticks in spring with a gas burner or with high-proof alcohol (methylated spirits) to kill harmful fungal spores from the previous year. It is best to insert the sticks into the soil right at the planting stage and turn the main shoots continuously through the coils in order to fix them in place.
If the roots have grown well, you can water the tomato plants more sparingly. Since the plants form a branched root system and can also supply themselves well with water, you should water when the plants leave the leaves hanging in the morning. Cherry tomatoes, whose water is mixed with sea water, remain smaller, but contain more flavourings and health-relevant antioxidants. For this, about four grams of sea salt per litre of rainwater are sufficient. It is important that the soil does not become salty. Otherwise nutrients such as calcium can no longer be absorbed. When watering, the general rule is never to wait until the soil has completely dried out. Not only the fruits of thin-skinned varieties such as ‘Yellow Pearshaped’ or ‘Bernese Rose’ burst open easily otherwise. Water especially the covered tomatoes regularly, in hot periods daily. As long as the soil is still cool, tempered water should be used.
In order to prevent fungal diseases such as late blight and brown rot, the tomato plants must be watered exclusively in the soil and the leaves must not be wetted. Bring it out with the watering can or shower directly in the root area. As wetting of the lower leaves can hardly be avoided, you should remove them as a precaution as soon as the plants are strong enough. If you cover the tomatoes with straw or grass cuttings, the plants will not cool down so quickly and the soil will remain loose. However, do not spread the mulch until the soil has been sufficiently heated.
Tomatoes need a lot of nutrients. Fertilize your tomatoes every 14 days from the start of flowering with a potassium-rich tomato fertilizer (specialist trade) or add some homemade nettle or comfrey liquid manure to the watering water.
In addition to tying, the removal of the shoots in the leaf axils has proved to be particularly effective. With this important care measure during the cultivation period, most tomato varieties yield the highest yield. The stinging shoots, which constantly grow out of the leaf axils, have to be constantly broken out from the young plant stage to the harvest as soon as they are discovered. If they are allowed to grow, the plants produce a lot of leaf mass, but hardly any fruit. The shoots should only be scattered by hand in dry weather and preferably in the morning. The degree of ambition depends on the variety: Cocktail tomatoes can be grown with several shoots, even some bush-shaped varieties do not need to be ambitious. And the closer the plants stand, the more ambitious they have to be. Tip: Pay close attention to the characteristics of the variety names, such as growth habit and width, in August you cut the shoot tip so that no new inflorescences grow; their fruits would not ripen anyway. Alternatively, only the newly growing inflorescences can be cut off, but the shoot tip can be protected. In the course of the culture, individual leaves become yellow starting from below – this is normal. One cuts them off, but preserves the healthy foliage to the end.
Harvesting and recycling
As long as they are still green, tomatoes contain the poisonous alkaloid solanine, which recedes as they mature. They are not harvested until they have fully developed their typical colour. In addition to vitamins B and C, tomatoes also contain many healthy minerals. In the field, the first tomatoes are ready for harvest at the end of July, in the greenhouse a month earlier. Fully ripened, they are the most aromatic. Before the first frosty night, the remaining green fruits are cut off and left on the windowsill. If you add an apple, the tomatoes ripen faster because fruit releases the ripening accelerating ethylene gas. There are no limits to the imagination when it comes to recycling: tomatoes taste great raw in salads, in sauces or ketchup or in soups.
Hardly any other vegetable has such a variety of varieties as tomatoes. When choosing a variety, the most important thing is the taste, which is mainly determined by the content of natural sugars and fruit acids. In addition to personal preference, the intended use also plays an important role. Meat tomatoes are usually low in fruit acid and harmonise well with other types of vegetables in the kitchen. Children especially like the small and sweet cocktail tomatoes, which are also good in salads or steamed on bread. Only varieties with high resistance to brown rot are suitable for outdoor cultivation from mid-May. In addition to modern hybrid breeds and naturally resistant wild tomatoes, some old varieties and newer organic breeds also meet this requirement.
Most varieties belong to the bar tomatoes. Hellfrucht’ and the early ‘Matina’ maintain their top position on the list of the most popular tomato varieties. Other recommended stave tomatoes are Resin Fire, Merano, Planet, Sonata (all F1 hybrids), and Golden Queen (yellow fruity). Tica’ comes from organic breeding and delivers a rich harvest in the small greenhouse. The yellow pear tomato ‘Yellow Submarine’ conquers not only the hearts of children with its pear-shaped fruits weighing only 15 grams. Banana Legs’ comes from North America and bears mild and sweet, light yellow, low juice fruits. Meat tomatoes have five or more fruit chambers. The newer meat tomato ‘Country Taste’ has smaller fruits than usual, but a pulp with a low stone content and an intense tomato taste. Crimson Crush’ is red, has a fruit weight of up to 200 grams and is resistant to brown rot. Ox-heart tomatoes (‘Cuore di bue’, ‘Coeur de boeuf’) are available with heart-shaped, smooth and strongly ribbed fruits. The largest copies can weigh more than 500 grams. Big Rainbow is decorated with orange stripes.
Sweet and small cherry and cocktail tomatoes: ‘Artisan Golden Bumble Bee’ is yellow-orange striped, round and fruity-sweet. Big Mama’ has a fruit weight of up to 250 grams, is low in kernel, suitable for soups, pasta sauces and tomato pesto. Chocolate Cherry’ is a new variety with black-red, spicy-sweet fruits and ideal for outdoor or greenhouse cultivation. The cherry tomato ‘Romello’ is a high-yielding snack tomato for boxes and plant pots. Golden Currant’, a hardy wild tomato with marmel-sized fruits, can be cultivated outdoors as well as in large pots. Sakura’ bears up to 20 fruits on each grape.
Buschtomatoes like ‘Dasher’ also grow in the pot on the terrace, mini buschtomatoes like ‘Tumbling Tom Yellow’ even fit in hanging baskets. ‘Rentita’ and ‘Balcony Star’ don’t need you to be stingy. Evita Basket’ is red, small and heart-shaped and predestined for hanging baskets and balcony boxes. Early Sibirian is a very early bushtomato variety. Indispensable in Italian cuisine are bottled tomatoes such as ‘San Marzano’. Roma’ bears firm, low juice, egg-shaped fruits, which are also suitable for grilling. New in this group is ‘Corianne’ with a pronounced fruity taste.
De Berao’ is particularly suitable for dried tomatoes. The tomato is floury, high-yielding and robust. Heavyweights like ‘Santa Lucia’ weigh up to 500 grams. Organic breeds such as ‘Primabella’ and ‘Primavera’, on the other hand, are asserting themselves in the field as in the bed.
Tomatoes are propagated by sowing. You can find more details under “Sowing” above.
Diseases and pests
The rather high susceptibility of tomatoes to disease is best controlled by selecting robust varieties and by maintaining good soil conditions. In general, susceptibility increases with increasing fruit size.
By far the most dangerous tomato disease is herb and brown rot (Phytophthora). It’s caused by a fungus, as mentioned earlier. Its spores are spread by the wind over long distances and quickly trigger an infection on the moist leaf surface. Also a high humidity and temperatures below 18 degrees Celsius favour the infestation. After infection, the disease can hardly be stopped. The damage can be seen on the foliage and shoots as well as on the fruit. The tomatoes turn brown, harden inside and become completely inedible. Remove the infected leaves immediately at the slightest sign of brown rot infestation. Instead of putting them on the compost, you should burn them. The most effective prevention is a roof over your head. If you do not have a greenhouse or tomato house, you can also use a translucent foil roof to prevent rain. Bridge plates or plastic tarpaulins can also help to counteract the fungus.
The frequently observed rolling of the leaves is not necessarily a disease. The reason for this is either overfertilisation or short-term water shortage. A brightening along the leaf veins in combination with a rolling up of the leaves, however, indicates an infestation with a viral disease. A lack of calsium is evident in the end rot of the flowers. When the weather is hot and dry, the fruit is sunken and brown at the end of the fruit. As a countermeasure you should ensure an even soil moisture.
I am Don Burke, one of the authors at My Garden Guide. I am a horticulturist that cultivates, grows, and cares for plants, ranging from shrubs and fruits to flowers. I do it in my own garden and in my nursery. I show you how to take care of your garden and how to perform garden landscaping in an easy way, step by step.I am originally from Sydney and I wrote in local magazines. Later on, I have decided, more than two decades ago, to create my own blog. My area of specialization is related to orchid care, succulent care, and the study of the substrate and the soil. Therefore, you will see many articles dedicated to these disciplines. I also provide advice about how to improve the landscape design of your garden.