Drivhusklubben/Greenhouse Forum/Gewächshausclub

08 Sep 2020 14:33

Sow your favourite tomato again and again

Did you have a tomato in your greenhouse this summer that was so nice you just need it again next year?

Helle Troelsen, a Danish garden adviser, ferments the seeds from her best tomatoes so she can use them year after year.

Get Helles guide here.

When the tomatoes are well-ripened, usually in September, I take seeds from those tomatoes I wish to propagate. At this time the seeds are fully developed. I take seeds from tomatoes I have tested and selected due to their taste and consistency.

Every year I buy seeds and test new tomato sorts. To breed tomatoes that look like the mother tomato I make sure the seeds are open-pollinated seeds and not F1-hybrids. If you propagate seeds from F1-hybrids you can’t be sure to get plants like the mother plant, as F1-hybrids typically are hybridizations of different sorts. A piece of good advice is to read on the seed bag if the seeds are F1-hybrids. If it doesn’t say F1-hybrid the seeds are open-pollinated seeds. Be aware of seeds bought in supermarkets as you can’t with certainty know if they are F1-hybrids or open-pollinated seeds.

Tomato seeds are wet seeds as they have an extra layer on the seed coat, which contains a sprout hampering matter. In nature, this extra layer will disappear when the tomato falls to the ground and decomposes. The seeds will stay in the ground and go through a fermentation process as the extra layer has disappeared. During the fermentation process, an antibiotic matter is formed which helps killing viruses and diseases. 

You can create the same process artificially by fermentation of the tomato seeds. Fermentation means that the seeds are going through this fermentation process which removes the sprout hampering layer and the bacteria, like fungi or viruses, that otherwise would have been transferred to the next generation of tomatoes.


The fermentation process

1: Scrape the wet seeds out of the tomato and put them in a container. I use small plastic pots with caps.

2: Pour a bit of water in – approximately 50/50. Put the cap on and note the name of the sort on the container. Place it in a warm place, like on the kitchen counter, but avoid direct sunlight.

3: Leave them for 2-4 weeks. Stir it once a day. Normally, the fermentation process will start after just one day and a layer of mould will cover the surface, which is a sign that the process has started. The fermentation decomposes the wet layer of the seeds and the mould form the matter which stops the development of bacteria, fungi and diseases. After 2-4 weeks the seeds should have sunk to the bottom and the wet layer dissolved.

4: Pour the seeds into a sieve and wash them in water, scrub off any remains of the wet layer until they are all clean.

5: Dry the seeds on a coffee filter for a week at room temperature and remember to write the name of the sort on the coffee filter. When the seeds are dry, they can be contained in the coffee filter or a paper bag, it should be a dry, dark and cool place until they are sown in April or next year. 


For Helle Troelsen the garden is a place where your senses get stimulated, and you will discover that there is more than just obligations and boring routines in your garden. A garden is a time warp of your own time, rhythm and cycle which you can enjoy. 

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