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Tomatoes

Verena Schmidt Verena SchmidtFolkert Siemens Folkert SiemensChristel Rupp Christel Rupp

Tomatoes are the most popular vegetable for self-cultivation. We provide you with variety tips and let you know what to watch out for when sowing, planting, and caring for these plants.

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Origin

Tomatoes (Solanum lycopersicum) are part of the nightshade family (Solanaceae) and originate from Central and South America. The fruiting vegetable was a permanent feature in the diet of the indigenous people of Latin America. The first tomatoes came to Europe as early as the 16th century, where they were first cultivated predominantly as decorative plants. Varieties with rich yields were first bred at the start of the 20th century. From then onwards, tomatoes began to be widely cultivated in our climes. Today, they are cultivated in almost every country in the world - and they are equally popular among both hobby and professional gardeners.

Appearance and Growth

Tomatoes are annual and grow between 7.87 inches (bush tomatoes) and 3.28 feet (stake tomatoes) tall. Their dark green, fleshy leaves are roughly pinnate and slightly hairy. The spicy fragrance tomatoes exude is unique. Up to 20 small, yellow flowers appear in the leaf axils from May; these are self-pollinating. The initially green berry fruit develops from these within two months, the fruit then turns a red, yellow, or blackish color, depending on the variety. Today, there are even some green tomato varieties available commercially.

In general, we differentiate between tomatoes according to their growth and fruit shape. There are:

  • Stake tomatoes (long main shoot which must be tied up),
  • Bush or balcony tomatoes (bushy growth and limited height growth),
  • Beef tomatoes (very large, ribbed fruit with five to ten capsules), and
  • Cherry or cocktail tomatoes (small, cherry or pear shaped fruit).
Flowering tomato plant

Yellow flowers and slightly hairy leaves and shoots are characteristic of tomatoes

Location and Soil

Tomatoes thrive in well-loosened, humus, and nutrient rich soils. 0.79 to 1.32 gallons of compost per 3 square feet - spread after soil preparation - ensures the basic provision of nutrients and improves the humus content of the soil. The plants react sensitively to heavy soils where waterlogging can form. A sunny, warm, sheltered place makes an ideal location.

There are different cultivation varieties: Tomatoes thrive in containers and pots in the greenhouse and outdoors. Small-growing balcony varieties, which grow to about 11.81 inches, such as ‘Miniboy’, can be successfully cultivated in pots. The pots and containers should have a capacity of at least 2.64 gallons. Take care to ensure that the water can flow off easily. Cultivation under a tomato house where temperatures never exceed 95 degrees Fahrenheit, even at the height of summer, is highly recommended. Plants can be led upwards with ties or stakes here.

Tomato houses are available from many large trade retailers. With a bit of skill you can also construct a house yourself from wooden lattices and UV-resistant greenhouse film. Important: The open sides must always face away from the weather side, meaning at our latitudes they may not be west facing. Completely enclosed houses or special tomato covers for outdoors are not recommended as permanent rain protection: Condensation forms under the film in fluctuating temperatures, creating favorable conditions for fungal disease infestations. This is why greenhouses where tomatoes are grown should be ventilated every day.

Tomato house

A tomato house protects the sensitive plants against the rain

Crop Rotation and Mixed Cultivation

As strong uptakers, tomatoes are in first position in crop rotation. They should be placed in a new plant bed every year. If the plants are always in the same position, soil pests such as lesion nematodes and Pyrenochaeta lycopersici pathogens can spread extensively. Low, heat-loving herbs, such as basil, can be placed along the rows. Tomatoes also make good neighbors for other plants: It is suspected that the scent of the tomato leaves wards off pests. Carrots, radishes, spinach, and cabbage all thrive in the vicinity of tomatoes. However, potatoes, peas, and fennel are not recommended as neighbors. Potatoes in particular should be avoided at all costs, as the fungal pathogen of the dreaded potato blight overwinters in these and infects the tomato plants in the spring.

Sowing

People who sow tomato seeds will often be confronted with the designations “ecological seeds” or “F1” on the seed packets. This indicates the manner in which the seeds were created - and this is a very important point, especially for self-sufficient individuals. Ecological seeds are so-called open-pollinating seeds. The parent plants are traditionally chosen over decades or even centuries through selection. Save the seeds from the harvested fruit and sow them again in the coming year and you will once again have tomatoes with the same properties, provided the plants have not interbred with other varieties.

F1 seeds on the other hand are harvested from seed breeders through a highly labor-intensive hybridization. Here, the desired features of the mother plants can be precisely combined through hybridization with the so-called F1 generation - the offspring. The seeds harvested from the hybridized parent species - the so-called F1 generation - are sold and are particularly high-performance. However, the plants do not have a secure heritage: If you collect their seeds and sow them again, the properties of the F2 generation will deviate heavily from the F1 generation.

It is not only ecological gardeners who have a critical view of the wide-spread of F1 seeds, as this is ultimately mainly a lucrative business for seed manufacturers as gardeners and farmers must buy these seeds new every year and cannot propagate them themselves. This also leads to the loss of more and more old, open-pollinating traditional varieties and that is a big problem in many developing countries, for example. There is no harm in using F1 seeds for your own requirements, however in many cases old tomato varieties are equally as robust, tasty, and high-yielding. You can now also by open-pollinating varieties from other places and not just from specialist providers - ecological tomato seeds are now also available in traditional garden centers, for example, the variety ‘Oxheart’.

No matter what seeds you use: The sowing and pre-cultivation of tomatoes is most successful under glass. Take care here not to sow the seeds to early. The period from the end of March until the start of April is ideal. Then tomato seeds can be sown sparsely in individual pots or seed trays and kept in very bright, moist conditions at 64.4 to 68 degrees Fahrenheit. This can be done on a light window ledge or in a small, heated greenhouse. The seeds will begin to germinate after eight to ten days.

Pre-cultivated tomato plants

Tomatoes should be pre-cultivated in pots from the end of March

After about three weeks, as soon as the saplings have developed their first leaf pair, prick them out individually into roughly 3.94 inch pots. Water the young plants continuously and only give them a brief dry period shortly before planting out in order to provide them with a stimulus for root growth.

Planting

If you have not brought on your tomatoes yourself, you can also buy saplings of all standard varieties from the spring in your garden center or order them from market gardening suppliers. More unusual varieties are usually only available as seeds. Many varieties of pre-cultivated young plants are now also available as grafts. The advantage: Plants grafted to strong growing wild tomatoes deliver up to 60 percent more fruit and are particularly suitable for cultivation on the balcony, patio, or in the greenhouse. The only disadvantage: The fruit tends to burst, so the plants are dependent on an even supply of water an nutrients.

As tomatoes do not tolerate frost, you should play things safe and wait until the final frosts are over before planting them outdoors. Of course, in an unheated greenhouse, an early planting schedule is not a problem. If you want to harvest early on without a greenhouse, you can plant the saplings outdoors at the end of April in a mild location and cover them with a film when there is a risk of night frosts. Remove the cover first thing in the morning and make sure that the film cover has distancing rings and ventilation holes. Prevent the film coming into contact with the leaves at all costs as this will increase the risk of a fungal infection.

Planting depth of tomato seedlings

Plant the tomato saplings so deep that the top of the pot ball is covered with 1.97 inches of soil. Then the plant will form additional roots

Tomatoes are strong uptakers: So you should fertilize the plant bed with compost and dung before planting and work this well into the soil. In addition, a planting distance of at least 19.69 x 23.62 inches ensures ventilation. Water the tomatoes thoroughly after planting. Refrain from watering the young plants in the following days to once again stimulate root growth. Ensure the tomatoes have a more secure footing by planting them up to the lowest leaf base, to ensure that the root base is covered with 1.97 to 3.94 inches of soil. In this way, the plants will form additional fine roots on the lower part of the stem, enabling them to absorb more nutrients. The pot ball should only just be visible for grafted tomatoes!

All tomatoes except bush tomatoes require a support structure. Spiral rods made from stainless steel or aluminum are practical and easy to clean. Disinfect the rods in the spring with a gas burner or high-percentage alcohol (methylated spirits) in order to kill off harmful fungal spores from the previous year. Ideally you should push the rods into the soil at the same time as planting and continuously wind the main shoot through the coils in order to fix it.

Supporting rod for tomatoes

Most tomato varieties require a support. A spiral rod, for example, is suitable for this

Care

If the roots have grown in well you can water the tomato plants more sparsely. As the plants form a branched root system and can also easily supply themselves with water, you should water when the plant leaves are hanging in the morning. Cherry tomatoes, whose water is staggered with salt water, remain smaller, however they have more flavor and health-benefiting antioxidants. Around 0.14 ounces of salt water per 0.26 gallons of rain water is enough. It is important here not to let the soil become oversalted. Otherwise it can no longer absorb nutrients such as calcium. In general, when watering: Never wait until the soil is fully dried out. Otherwise, it is not only the fruit of the thin-skinned varieties such as ‘Yellow Pearshaped’ or ‘Berner Rose’ that will easily burst. Water covered tomatoes regularly in particular; daily during hot periods. You should use temperate water, provided the soil is not cool.

Watering tomatoes

The most important rule when watering: Only water the soil area wherever possible

In order to prevent fungal diseases such as blight, you should only water the tomato plants in the soil area and avoid wetting the leaves. Direct the watering can or spray directly in the root area. As it is almost impossible to avoid wetting the lower leaves, you should carefully remove these as soon as the plants are strong enough. Regularly pruning the tomatoes also prevents blight from spreading.

If you cover the tomatoes with straw or grass cuttings, do not cool the plants down too quickly and the soil will remain loose. However, only bring out the mulch if the soil has warmed up sufficiently.

Tomatoes require a lot of nutrients. Fertilize your tomatoes every 14 days from the start of flower formation with a potassium-rich tomato fertilizer (trade shop) or add a little homemade stinging nettle or comfrey liquid manure to the water.

Removing epicormic tomato shoots

During thinning the shoots are removed from the leaf axils. This makes the plants form more fruit

In addition to tying up, removing epicormic shoots, i.e. the shoots in the leaf axils, is also a proven technique. Applying these important maintenance measures during the cultivation period will lead most tomato varieties to put out the highest yield. The continually growing new shoots from the leaf axils must be broken off continuously as soon as they are discovered: from the young plant stage until the harvest. If they are allowed to grow, the plants will produce lots of foliage but barely any fruit. You should only remove the epicormic shoots in dry weather by hand, and ideally in the morning. The amount of epicormic shoots that should be removed depends on the variety: Cocktail tomatoes can be readily grown on several shoots, even some bush forms do not require the removal of epicormic shoots. Plus: The more closely together the plants are, the more epicormic shoots should be removed. Tip: Pay close attention to the properties and growth shape and width for the variety name.

Trim the shoot tips in August to ensure that no new inflorescences grow in; the fruit from these flowers will no longer ripen anyway. Alternatively, only prune the newly growing inflorescences, but leave the shoot tips. During cultivation some individual plants start out yellow from beneath - this is normal. Prune these but leave the healthy foliage until the end.

It is not generally worth overwintering tomatoes. But you can give it a try with well maintained bush tomatoes that are kept in pots on the balcony and are still healthy at the end of the season.

Harvesting and Use

Many people wonder whether green tomatoes are edible or poisonous. They do indeed contain the poison alkaloid solanine that can build up with increased maturity. They should only be harvested if their variety-typical color has fully formed. Then the tomatoes also have lots of healthy minerals in addition to vitamins B and C. Outdoors, the first tomatoes are ready to harvest at the end of July, a month earlier in the greenhouse. They are most aromatic when they have fully ripened. Cut of the remaining, still green fruit before the first overnight frosts and leave the tomatoes to ripen off the vine by storing them indoors. If you place them together with apples, the tomatoes will ripen more quickly as the fruit gives off ethylene gas which accelerates ripening. When remember: Never put them in the fridge!

There are no limits when it comes to using tomatoes: They taste great raw in a salad, cooked in a sauce or in soups. You can increase the shelf-life of tomatoes by boiling them down or making your own ketchup. Strained tomatoes are also easy to make yourself.

Variety Tips

There are hardly any other vegetables that demonstrate the kind of range of varieties of tomatoes. Taste is king when it comes to choosing a variety, and this is predominantly determined by the content of natural sugars and fruit acids. In addition to personal preference, the intended purpose also plays a role. Beef tomatoes are generally low in fruit acids and harmonize well with other types of vegetables in the kitchen. The little, sweet cocktail tomatoes are particularly popular with children: these tomatoes can also be used in a salad or steamed and spread on bread. Only varieties with a high tolerance to blight can be considered for cultivation outdoors from the middle of May. In addition to hybrid breeds and the naturally resistant wild tomatoes, some old varieties and newer organic breeds also fulfil this requirement.

Stake tomato ‘Banana Legs’ (left) and beef tomato (right)

Most varieties are stake tomatoes. ‘Hellfrucht’ and the early ‘Matina’ maintain their top position on the list of the most popular tomato varieties. Further recommended stake tomatoes are ‘Harzfeuer’, ‘Meran’, ‘Planet’, ‘Sonata’ (all F1 hybrids), and ‘Golden Queen’. ‘Tica’ originates from ecological breeding and delivers a rich harvest in small greenhouses. The yellow pear tomato ‘Yellow Submarine’ is not only a favorite among children with its tiny, 0.53 ounce pear-shaped fruit. ‘Banana Legs’ comes from North America and has mild, sweet, light-yellow, less juicy fruit.

Beefsteak tomatoes have five or more fruit chambers. The new beef tomato ‘Country Taste’ has smaller fruit than usual, however its fruit flesh has few seeds and an intensive tomato flavor. ‘Crimson Crush’ is red with a fruit weight of up to 7.05 ounces and is resistant against blight. Oxheart tomatoes (‘Cuore di bue’, ‘Coeur de boeuf’) are available with heart-shaped, smooth and heavily ribbed fruit. The largest examples can weigh more than 17.64 ounces. ‘Big Rainbow’ is decorated with orange stripes.

Sweet, small cherry and cocktail tomatoes: ‘Artisan Golden Bumble Bee’ is yellow and orange striped, round and fruity-sweet. The fruit of ‘Big Mama’ weighs up to 8.82 ounces, has few seeds, and is suitable for soups, pasta sauces, and tomato pesto. ‘Chocolate Cherry’ is a new breed with black-red, spicy-sweet fruit; it is perfect for cultivating outdoors or in a greenhouse. The ‘Romello’ cherry tomato is a high-yielding snack tomato for boxes and plant containers. ‘Golden Currant’ is a resistant wild tomato with marble-sized fruit that can be cultivated both outdoors and in large pots. ‘Sakura’ bears 20 pieces of fruit on each cluster.

‘Chocolate Cherry’, a black-red cocktail tomato

‘Chocolate Cherry’, a black-red cocktail tomato

Bush tomatoes such as ‘Dasher’ also grow in pots on the patio, mini bush tomatoes such as ‘Tumbling Tom Yellow’ even fit in hanging baskets. ‘Rentita’ and ‘Balkonstar’ do not require thinning. ‘Evita Basket’ is red, small and heart-shaped and almost made for hanging baskets and window boxes. ‘Early Siberian’ is a very early bush tomato variety. Plum tomatoes such as ‘San Marzano’ are indispensable in Italian cuisine. ‘Roma’ has firm, low-juice, ovate fruit that is also suitable for grilling. ‘Corianne’ with its pronounced, fruity flavor is new to this group.

Marzano tomatoes

Marzano tomatoes are particularly suitable for sauces due to their powerful, fruity aroma

‘De Berao’ are particularly good as dried tomatoes. The tomatoes are floury, high-yielding, and robust. Heavy-weights such as ‘Santa Lucia’ reach about 17.64 ounces on the weighing scales. Ecological breeds such as ‘Primabella’ and ‘Primavera’, on the other hand, hold their ground both in the field and in the plant bed.

Propagation

Tomatoes are propagated through sowing. You can find more details under the heading ‘Sowing’ earlier on this page.

Diseases and Pests

The best way to control the extremely high susceptibility of tomatoes to diseases is to select robust varieties and ensure good soil conditions. The susceptibility generally grows with increasing fruit size.

By far the most dangerous tomato disease is (Phytophthora). As already mentioned, it is caused by a fungus. Its spores are spread by the wind over long distances and quickly trigger an infection on damp leaf surfaces. High humidity and temperatures below 64.4 degrees Fahrenheit are also favorable for an infestation. Once an infection has taken hold, the disease is almost impossible to stop. Its damaging effects can bee seen both on the leaves and shoots, as well as the fruit. The tomatoes turn brown, harden on the inside and are completely inedible. Remove infected leaves immediately at even the slightest indication of blight. These should not be placed on the compost, but burned. The most effective prevention is a roof overhead. If you do not have a greenhouse or a tomato house, a transparent overhead cover made from film that holds off the rain is also for prevention. Multi-skin sheets or plastic tarps can also help to combat the fungus.

Blight on tomatoes

Blight often occurs in high humidity. You should only water the lower leaves to prevent an infestation

The commonly observed rolled leaves do not necessarily mean a disease. This is caused by either over-fertilizing or a short-term lack of water. Lightening along the leaf veins in combination with rolled leaves, however, indicates a viral infection. A lack of calcium is indicated by blossom-end rot. In hot, dry weather, the fruit ends are depressed and brown. Ensure evenly moist soil as a countermeasure. Occasionally, a soft-bodied mite infestation may occur, this can be recognized, among other things, by stunted and twisted leaves.

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