TOMATOES
Lycopersicon lycopersicum
Family: Solanaceae
Tomato seed saving guide also available here as a PDF document (137Kb)
Tomatoes are generally divided into bush or cordon types. Bush tomatoes have several branches, each of which terminates with a flower truss, so the plant forms a bush. Cordons generally have a single major shoot, with trusses (and side shoots) from the axil between leaf and stalk, so the main shoot may form a very long vine. Both these classifications (like the distinction between greenhouse and outdoor) and somewhat arbitrary. Tomatoes are mostly easy to save seed from and, with a few exceptions, easy to keep true to type.
Growing and Roguing
- Grow as you would for eating. In Britain tomatoes are treated as annuals, producing seed the same year that they are planted.
- Tomatoes can usually produce seed outside, though varieties that are slow to grow and ripen do best in a greenhouse or polytunnel.
- Tomatoes are inbreeders and many seedsavers successfully maintain varieties by saving from just two or three plants, though it would be better to save from at least six plants.
- Remove any plants which look sickly or have different foliage to the rest, or any which produce tomatoes different to the rest.
Tomato flower with
protruding stigma
Pollination and Isolation
Most tomatoes are not capable of cross-pollination because in modern varieties the flowers are perfect and self-pollinating (the female stigma is inside a cone of male anthers). This means that different varieties can be grown close together.
However, there are three exceptions: currant tomatoes (Lycopersicon pimpinellifolium), potato leaved varieties, and double blossoms on beefsteak varieties. These often have a protruding stigma and are able to cross-pollinate, especially if there are other protruding-stigma varieties in the vicinity. To be absolutely certain, check a few newly opened flowers using a hand lens. The green stigmas will protrude from the anther tube. For safety, you could grow just one protruding stigma variety a year. If you are growing more than one 'protruding stigma' type, you need to bag the individual trusses or isolate these plants in a mesh cage. The flowers will self-pollinate within the cage or bag.
Harvesting
The seeds are fully mature once the tomatoes are ripe. Allow the fruits to ripen on the plants, if possible, or bring the fruits indoors and ripen them as you would for eating, e.g. in a box or drawer with ripe apples or bananas.
Cleaning Seed
Some varieties contain more seed than others. Large beefsteak or plum tomatoes may yield less than ten seeds, while small or cherry tomatoes can produce scores of seed.
To save a small quantity of seeds
Remove seeds from the fruit and rinse in a sieve under cold running water, rubbing them against the sieve to remove the gel. Spread on paper towel or kitchen paper, label, and leave to dry. In spring you can plant the paper towel with the seeds attached (or cut out to plant individually) into moist compost in a seed tray to start the plants.
To save a larger quantity of seed - soda crystals method
Dissolve 1tsp of soda crystals in a little hot water in a jam jar and fill two-thirds full with cold water. Remove seeds from the fruit and rinse them in a sieve under cold running water, rubbing them against the sieve to remove the gel. Add the seeds to the jam jar and label. After 24 hours the gel coat should have broken down; if not leave it another day. Rinse the seeds in a sieve, again rubbing them against the sieve to remove the last of the gel. Spread them thinly, so none are overlapping, onto a clean, dry surface (e.g. a lunchbox lid or plate). Label and leave to dry. Collect the dry seeds and store in a labelled envelope.
To save a larger quantity of seed - fermentation method
Fermenting tomato seeds
Squeeze the pulp from ripe tomatoes into a suitable container (e.g. large yoghurt pots or small plastic buckets). You can also put the ripe fruits into a food processor with an equal quantity of water and process until you have a pulpy mass. The seeds are hard and will not be damaged.
Put the container into a warm place, where it will begin to ferment. The smell can be overpowering but it is good for the seeds. Fermentation removes compounds that inhibit germination and also destroys seed-borne diseases. You are merely duplicating what happen to a ripe tomato in nature.
After three or four days, when the bucket is topped by a horrible mass of slimy mould, add plenty of water and stir vigorously. Good seeds will settle to the bottom so you can tip the rotting mass away. Rinse and repeat until only good, clean seeds remain. Pour the seeds into a strainer and place them on a clean plate or piece of glass (they will stick to paper). Stir once or twice a day to promote even drying and prevent clumps of seeds forming. They may germinate if not dried quickly, but do not use either direct sunlight or an oven. A cool, gentle breeze is best.
Storage
Tomato seeds will last in storage for about six years.
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