CULTIVATION OF TOMATO SEEDS.
TOMATO BOTANY AND CROSS FERTILIZATION RISKS:
Lycopersicon, which means wolf-peach, is a species of the family Solanaceae. Except for lycopersicum, our common tomato, there are also eight other kinds of tomato in this family. Several of these are used in modern tomato breeding to incorporate resistance from different kinds of attacks. Of these the only one to be grown to some extent for consumption is L. pimpinellifolium, currant tomato, which has small fruits. They can all be annuals or perennials depending on the climate zone they live in. In latitudes without frost they are perennials but are annuals in the north of Europe.
The original tomatoes were, largely, cross-fertilizing and it was not until they arrived in Europe and went north where there were no suitable insects, that self-fertilization became dominant. In the common lobate-leaved varieties, the pistil has retro-developed and is hidden in a dense cone of stamens and the risk of cross-fertilization is extremely slight, estimated to be 0,5 "“ 2%. Variants with so called potato tops, double-blooming beef-steak tomatoes and the currant tomato, L. pimpinellifolium, do have long pistils which reach out from the stamens and the risk of cross-fertilization rises dramatically to 5"“10 % and is a lot greater for the currant tomato. Normally, the insects aren"™t particularly interested in the small yellow tomato flower with its minimal contents of nectar and pollen. But if there is nothing else around and the opening of the flowers has been delayed by cool weather, occasionally the bee or bumblebee especially, can cause cross-fertilizations. To secure good and speedy fertilization, especially in greenhouses, the plants should be shaken a little to aid the pollen in reaching the stigmas of the pistils; outdoors the wind usually takes care of that. For hobby growers it is most important to get seeds for next year"™s tomato plants and the odd cross fertilization doesn"™t matter. Several sorts may grow together, but it is a good idea to keep other flowering crops between them. When growing seeds professionally or for seed-banks, or just wanting to keep your sorts pure, a distance of at least 50 m between them is sufficient, or preferably 200 m, depending a little on which species of tomato you grow. If the spaces between the different sorts are smaller, you could cover the tomato plants with plant cloth. That will certainly stop the insects. Do so if you really want no cross-fertilization whatsoever.
Generally the tomato is considered to be a bisexual self-fertilizer, however without risk of the genetic damage normally occurring by inbreeding.
TOMATO CULTIVATION:
The tomato needs well-fertilized soil rich in phosphorus and humus, with the ability to retain moisture with a PH-value between 6,0 and 7,0. However, too much nitrogen and water causes overgrown tops and soft fruits which easily rot. To avoid contamination, Potatoes must not have been grown in the same soil for the past 6 years. Tomatoes however, may be grown in the same soil for years as long as they keep healthy. The tomato needs heat and sun and must grow in a sheltered place or a greenhouse. Ground cover is good after the soil has warmed up. If the temperature in the greenhouse reaches more than 30°C, airing the greenhouse is necessary. If not, the tomatoes could let go of their flowers and that would obviously cause poor fertilization. Likewise, if the night temperature is less than 13°C or above 23°C. The potato varieties that have leaves are the most sensitive to high temperatures.
Tomatoes are rarely attacked by insects, with the exception of aphids and whitefly, which can cause problems in greenhouses. Fight them repeatedly with showers of tansy-, garlic- and wormwood teas or with pyrethrum and rotenone if the attacks are stubborn. Several varieties of fungi, bacteria and viruses are far greater threats to the tomatoes. Set out only healthy, strong plants and strengthen their resistance with repeated showers of nettle water and extracts of algae and other preparations. Avoid planting too closely and burn all affected parts of the plants, if attacked. Especially in greenhouses, it is good to sprinkle the tomatoes now and then, with water mixed with skimmed milk and also teas of garlic and yellow onion peel, to further hinder and fight attacks.
Tomatoes thrive in the company of the onion family, parsley, basil, cress and carrot, but dislike the presence of potatoes, fennel and corn anywhere near.
Tomatoes are usually grouped as greenhouse tomatoes and field tomatoes. The limits are fleeting and many so-called greenhouse tomatoes can grow well outdoors and likewise field tomatoes can grow in greenhouses. The very tall (6-8 m) typical greenhouse tomatoes that market gardeners use, cannot live in outdoor climates. Nowadays, these sorts are predominately F1-hybrids. Tomatoes are also grouped according to size: tall, medium and short. Another grouping is according to the size of the fruit, from red currant tomato to beef tomato. Shape is also used to group the various sorts: flattened round, cherry, plum, drop-shaped etc. Finally, you could group them according to their use, such as: tomatoes for pasta, tomatoes for juice, for salad, for drying etc.
Sow indoors 7-8 weeks before setting out, just under 1 cm deep. Basically, in February-March for greenhouse seedlings (unheated greenhouses) and March-April for outdoors seedlings. The best germination temperature is 22-23°C. Then the seeds normally would germinate in 5-14 days. If the temperature is lower, it might take 4 weeks before the seedlings appear. Place the seedlings in a light and airy place, preferably at a temperature of about 18°C. When a few real leaves have appeared, the plants can be potted. Now the temperature can be lowered a little, especially at night.
Temper the plants gradually before setting out, especially the ones destined for outdoors. Do not set out until the risk of frost at night is completely over and the nightly temperature keeps above 7°C. Tomato plants for a temperature controlled greenhouse, can of course be set out earlier, as soon as the soil has warmed up a bit.
Plant them a bit deeper than they were in the pots and never allow them to dry out completely. Tomatoes grow roots along the whole stem so overgrown plants can be planted deeply or lying under-ground with only the top above ground. Too early sowing and setting out of tomato plants, spoils their growth and cause lanky plants and poor yield. Do not hurry the sowing if you don"™t have a really good nursery.
Tomatoes need a mutual distance of 35-55 cm. If the tall and medium sized sorts are grown outdoors in enclosures or net cages, without pinching out the shoots in the axils, a much greater distance between the plants is needed, up to 1.5 m.
Pick the fully ripe and sun-warmed tomatoes for eating. If there is risk of nightly frosts before all the tomatoes are ripe, they can ripen indoors in a cool, dark place (8-12°C). The whole de-leaved plants can also be hung up indoors, upside-down, and harvested gradually.
TOMATO SEED HARVEST:
The tomato, botanically speaking, is a "˜swelling of the walls around the ovary of the flower, with rooms filled with seeds and fruit juice"™, and is classed as a berry.
The fruits ripen unevenly on the plant and must be harvested every now and then. Only fully ripe tomatoes yield good seeds. The colour should be well developed and the fruit feel soft when you squeeze it. The small leaves at the fastening should show a tendency to dry up. Harvest fruits only from completely healthy plants, and only fruits typical of the sort. Do this from several different plants to keep the all-important genetic variation.
The seed-rooms are clearly visible if you cut the fruit in halves along the "equator" not through the fastening and the flower. The least hint of green colour in the jelly-like substance around the seeds, shows that the fruit is not fully ripe. Those tomatoes are for the pot or the freezer. Only fully-ripe fruits with yellow seeds and clear or slightly orange-red gel should be harvested. The gel around the seeds contains substances, which prevent germination inside the warm moist tomato, and protect the seeds from various bacteria and viruses. If the fruit is allowed to fall to the ground it soon begins to rot and ferment and the jelly-like substance is dissolved. This process kills bacteria and fungi that could harm the seed and the plant when it begins to germinate and grow.
There are several ways of harvesting and treating the seeds.
1. If you harvest just one or two tomatoes, you can just squeeze them and scatter the seeds on a piece of kitchen roll and allow them to dry so they stick to the paper. Fold the paper and write the name of the sort and the date on the paper and save until sowing. Then you just tear off a piece of paper with a couple of seeds and plant it, and so on. The disadvantage with this method is that you bypass the useful normal fermentation process, which would kill "bad bacteria".
2. If you have a larger crop, up to a bucketful of seed tomatoes, it is easiest to cut the tomatoes at the "equator" and squeeze the pulp and seeds and gel out over a bowl. Pour the mass into a glass jar with lid and add water to a 1/4 - 1/3 of the volume, to help start the fermentation. Write the name of the sort and date on the jar. The jar should not be more than half-full to enable you to shake it at least twice daily during fermentation, without it welling over. Open the lid and let in oxygen after shaking. If it"™s impossible to shake the jar due to too much content, stir the contents with a fork or spoon.
The fermentation needs 2-5 days depending on temperature, ripeness and sort. If the temperature is too high the fermentation process goes quickly and a lot of the bacteria survive. On the other hand, if it is too cold the process lasts a long time and the seeds begin to germinate in the soup. The best result is achieved with 21-25°C. On top of the refrigerator is usually an excellent place for fermentation. Already after 24 hours there is a cover of grey-white mold on the surface and the typical smell of fermenting, moldy tomatoes when you open the lid.
When the seeds fall to the bottom of the jar after shaking, the fermentation is done. Fill the jar with cold water and allow the seeds to fall to the bottom. Then carefully pour out the soup of fruit mass and unripe seeds. Pour in more water and repeat the procedure until the water is clear. Unripe seeds float or sink slowly and are thrown out with the water.
Pour the seeds into a sieve and rinse thoroughly under running water. Shake off as much water as possible and then pour out the seeds onto a towel. Fold the towel and press the water out. With a knife, scrape off the seeds that are stuck onto the towel and pour them out on a dry towel and continue to press out more water.
Scatter the seeds onto netting to allow them to dry as quickly as possible in an airy place but not in direct sunlight. A seed-drying machine that can deliver 40°C, dries the seeds in 5-6 hours. A hair-dryer or fan on cool setting, works wonders during rainy periods. The faster it dries, the better. During drying it is important to rub the seeds to prevent them from sticking together.
3. If you harvest buckets full of tomatoes, it is easier to just cut them and see that they are ripe. Then just use a potato masher, pureeing machine or meat grinder, which doesn"™t harm the seeds, or a kitchen machine on slow speed with blunt knives. The mass of fruit is poured into a clean bucket or drum covered to allow it to ferment as above. Stir several times a day and when bubbles appear on the surface and there is a thick layer of mold, scoop up the fruit meats and rinse the rest in several changes of water. Dry as above.
Good quality seeds that are kept in a cool and dry place keep their fertility for up to 10 years. Storing the seeds in a freezer prolongs the storage time with many years, but then the seeds must be very carefully dried for several weeks before storing them in airtight containers for the freezer and afterwards allowed to regain room temperature without being exposed to air. Otherwise, condensation will begin, with harmful consequences for the seeds.
300-350 seeds usually weigh 1 g, but in some sorts with small seeds it is the double amount/g.
Growing seeds for tomatoes contradicts the old saying that you cannot have the cake and keep it. After removing the seeds you still have the fruit-flesh left to eat.
TOMATO BOTANY AND CROSS FERTILIZATION RISKS:
Lycopersicon, which means wolf-peach, is a species of the family Solanaceae. Except for lycopersicum, our common tomato, there are also eight other kinds of tomato in this family. Several of these are used in modern tomato breeding to incorporate resistance from different kinds of attacks. Of these the only one to be grown to some extent for consumption is L. pimpinellifolium, currant tomato, which has small fruits. They can all be annuals or perennials depending on the climate zone they live in. In latitudes without frost they are perennials but are annuals in the north of Europe.
The original tomatoes were, largely, cross-fertilizing and it was not until they arrived in Europe and went north where there were no suitable insects, that self-fertilization became dominant. In the common lobate-leaved varieties, the pistil has retro-developed and is hidden in a dense cone of stamens and the risk of cross-fertilization is extremely slight, estimated to be 0,5 "“ 2%. Variants with so called potato tops, double-blooming beef-steak tomatoes and the currant tomato, L. pimpinellifolium, do have long pistils which reach out from the stamens and the risk of cross-fertilization rises dramatically to 5"“10 % and is a lot greater for the currant tomato. Normally, the insects aren"™t particularly interested in the small yellow tomato flower with its minimal contents of nectar and pollen. But if there is nothing else around and the opening of the flowers has been delayed by cool weather, occasionally the bee or bumblebee especially, can cause cross-fertilizations. To secure good and speedy fertilization, especially in greenhouses, the plants should be shaken a little to aid the pollen in reaching the stigmas of the pistils; outdoors the wind usually takes care of that. For hobby growers it is most important to get seeds for next year"™s tomato plants and the odd cross fertilization doesn"™t matter. Several sorts may grow together, but it is a good idea to keep other flowering crops between them. When growing seeds professionally or for seed-banks, or just wanting to keep your sorts pure, a distance of at least 50 m between them is sufficient, or preferably 200 m, depending a little on which species of tomato you grow. If the spaces between the different sorts are smaller, you could cover the tomato plants with plant cloth. That will certainly stop the insects. Do so if you really want no cross-fertilization whatsoever.
Generally the tomato is considered to be a bisexual self-fertilizer, however without risk of the genetic damage normally occurring by inbreeding.
TOMATO CULTIVATION:
The tomato needs well-fertilized soil rich in phosphorus and humus, with the ability to retain moisture with a PH-value between 6,0 and 7,0. However, too much nitrogen and water causes overgrown tops and soft fruits which easily rot. To avoid contamination, Potatoes must not have been grown in the same soil for the past 6 years. Tomatoes however, may be grown in the same soil for years as long as they keep healthy. The tomato needs heat and sun and must grow in a sheltered place or a greenhouse. Ground cover is good after the soil has warmed up. If the temperature in the greenhouse reaches more than 30°C, airing the greenhouse is necessary. If not, the tomatoes could let go of their flowers and that would obviously cause poor fertilization. Likewise, if the night temperature is less than 13°C or above 23°C. The potato varieties that have leaves are the most sensitive to high temperatures.
Tomatoes are rarely attacked by insects, with the exception of aphids and whitefly, which can cause problems in greenhouses. Fight them repeatedly with showers of tansy-, garlic- and wormwood teas or with pyrethrum and rotenone if the attacks are stubborn. Several varieties of fungi, bacteria and viruses are far greater threats to the tomatoes. Set out only healthy, strong plants and strengthen their resistance with repeated showers of nettle water and extracts of algae and other preparations. Avoid planting too closely and burn all affected parts of the plants, if attacked. Especially in greenhouses, it is good to sprinkle the tomatoes now and then, with water mixed with skimmed milk and also teas of garlic and yellow onion peel, to further hinder and fight attacks.
Tomatoes thrive in the company of the onion family, parsley, basil, cress and carrot, but dislike the presence of potatoes, fennel and corn anywhere near.
Tomatoes are usually grouped as greenhouse tomatoes and field tomatoes. The limits are fleeting and many so-called greenhouse tomatoes can grow well outdoors and likewise field tomatoes can grow in greenhouses. The very tall (6-8 m) typical greenhouse tomatoes that market gardeners use, cannot live in outdoor climates. Nowadays, these sorts are predominately F1-hybrids. Tomatoes are also grouped according to size: tall, medium and short. Another grouping is according to the size of the fruit, from red currant tomato to beef tomato. Shape is also used to group the various sorts: flattened round, cherry, plum, drop-shaped etc. Finally, you could group them according to their use, such as: tomatoes for pasta, tomatoes for juice, for salad, for drying etc.
Sow indoors 7-8 weeks before setting out, just under 1 cm deep. Basically, in February-March for greenhouse seedlings (unheated greenhouses) and March-April for outdoors seedlings. The best germination temperature is 22-23°C. Then the seeds normally would germinate in 5-14 days. If the temperature is lower, it might take 4 weeks before the seedlings appear. Place the seedlings in a light and airy place, preferably at a temperature of about 18°C. When a few real leaves have appeared, the plants can be potted. Now the temperature can be lowered a little, especially at night.
Temper the plants gradually before setting out, especially the ones destined for outdoors. Do not set out until the risk of frost at night is completely over and the nightly temperature keeps above 7°C. Tomato plants for a temperature controlled greenhouse, can of course be set out earlier, as soon as the soil has warmed up a bit.
Plant them a bit deeper than they were in the pots and never allow them to dry out completely. Tomatoes grow roots along the whole stem so overgrown plants can be planted deeply or lying under-ground with only the top above ground. Too early sowing and setting out of tomato plants, spoils their growth and cause lanky plants and poor yield. Do not hurry the sowing if you don"™t have a really good nursery.
Tomatoes need a mutual distance of 35-55 cm. If the tall and medium sized sorts are grown outdoors in enclosures or net cages, without pinching out the shoots in the axils, a much greater distance between the plants is needed, up to 1.5 m.
Pick the fully ripe and sun-warmed tomatoes for eating. If there is risk of nightly frosts before all the tomatoes are ripe, they can ripen indoors in a cool, dark place (8-12°C). The whole de-leaved plants can also be hung up indoors, upside-down, and harvested gradually.
TOMATO SEED HARVEST:
The tomato, botanically speaking, is a "˜swelling of the walls around the ovary of the flower, with rooms filled with seeds and fruit juice"™, and is classed as a berry.
The fruits ripen unevenly on the plant and must be harvested every now and then. Only fully ripe tomatoes yield good seeds. The colour should be well developed and the fruit feel soft when you squeeze it. The small leaves at the fastening should show a tendency to dry up. Harvest fruits only from completely healthy plants, and only fruits typical of the sort. Do this from several different plants to keep the all-important genetic variation.
The seed-rooms are clearly visible if you cut the fruit in halves along the "equator" not through the fastening and the flower. The least hint of green colour in the jelly-like substance around the seeds, shows that the fruit is not fully ripe. Those tomatoes are for the pot or the freezer. Only fully-ripe fruits with yellow seeds and clear or slightly orange-red gel should be harvested. The gel around the seeds contains substances, which prevent germination inside the warm moist tomato, and protect the seeds from various bacteria and viruses. If the fruit is allowed to fall to the ground it soon begins to rot and ferment and the jelly-like substance is dissolved. This process kills bacteria and fungi that could harm the seed and the plant when it begins to germinate and grow.
There are several ways of harvesting and treating the seeds.
1. If you harvest just one or two tomatoes, you can just squeeze them and scatter the seeds on a piece of kitchen roll and allow them to dry so they stick to the paper. Fold the paper and write the name of the sort and the date on the paper and save until sowing. Then you just tear off a piece of paper with a couple of seeds and plant it, and so on. The disadvantage with this method is that you bypass the useful normal fermentation process, which would kill "bad bacteria".
2. If you have a larger crop, up to a bucketful of seed tomatoes, it is easiest to cut the tomatoes at the "equator" and squeeze the pulp and seeds and gel out over a bowl. Pour the mass into a glass jar with lid and add water to a 1/4 - 1/3 of the volume, to help start the fermentation. Write the name of the sort and date on the jar. The jar should not be more than half-full to enable you to shake it at least twice daily during fermentation, without it welling over. Open the lid and let in oxygen after shaking. If it"™s impossible to shake the jar due to too much content, stir the contents with a fork or spoon.
The fermentation needs 2-5 days depending on temperature, ripeness and sort. If the temperature is too high the fermentation process goes quickly and a lot of the bacteria survive. On the other hand, if it is too cold the process lasts a long time and the seeds begin to germinate in the soup. The best result is achieved with 21-25°C. On top of the refrigerator is usually an excellent place for fermentation. Already after 24 hours there is a cover of grey-white mold on the surface and the typical smell of fermenting, moldy tomatoes when you open the lid.
When the seeds fall to the bottom of the jar after shaking, the fermentation is done. Fill the jar with cold water and allow the seeds to fall to the bottom. Then carefully pour out the soup of fruit mass and unripe seeds. Pour in more water and repeat the procedure until the water is clear. Unripe seeds float or sink slowly and are thrown out with the water.
Pour the seeds into a sieve and rinse thoroughly under running water. Shake off as much water as possible and then pour out the seeds onto a towel. Fold the towel and press the water out. With a knife, scrape off the seeds that are stuck onto the towel and pour them out on a dry towel and continue to press out more water.
Scatter the seeds onto netting to allow them to dry as quickly as possible in an airy place but not in direct sunlight. A seed-drying machine that can deliver 40°C, dries the seeds in 5-6 hours. A hair-dryer or fan on cool setting, works wonders during rainy periods. The faster it dries, the better. During drying it is important to rub the seeds to prevent them from sticking together.
3. If you harvest buckets full of tomatoes, it is easier to just cut them and see that they are ripe. Then just use a potato masher, pureeing machine or meat grinder, which doesn"™t harm the seeds, or a kitchen machine on slow speed with blunt knives. The mass of fruit is poured into a clean bucket or drum covered to allow it to ferment as above. Stir several times a day and when bubbles appear on the surface and there is a thick layer of mold, scoop up the fruit meats and rinse the rest in several changes of water. Dry as above.
Good quality seeds that are kept in a cool and dry place keep their fertility for up to 10 years. Storing the seeds in a freezer prolongs the storage time with many years, but then the seeds must be very carefully dried for several weeks before storing them in airtight containers for the freezer and afterwards allowed to regain room temperature without being exposed to air. Otherwise, condensation will begin, with harmful consequences for the seeds.
300-350 seeds usually weigh 1 g, but in some sorts with small seeds it is the double amount/g.
Growing seeds for tomatoes contradicts the old saying that you cannot have the cake and keep it. After removing the seeds you still have the fruit-flesh left to eat.
