Seed saving

Saving 5 varieties of tomato seeds using the fermentation method, waiting for mould to form on the top (yes, really).

As seeds are ripening in the garden now is time to think about which seeds to save for sowing next year, or pass on to friends for their gardens. It’s an easy and satisfying process and we even have a seed packet (at the bottom of this screen) that you can print out and make up to store them in.

Seeds for saving fall into 2 categories: dry, like poppies, beans etc. or wet, like tomatoes or squashes, which are encased in fruit. Bearing in mind for both categories, you should make sure that the plant you are taking the seed from is an open pollinated or heritage/heirloom variety not a hybrid variety to ensure that the seeds will come true to the parent plant.

Saving dry seeds

Collect ripe seed on a dry day, as soon as the seedheads (e.g. capsules or pods) ripen - often indicated by a colour change from green to brown. Pick the seedheads and lay them out to dry on a greenhouse bench, warm windowsill or in an airing cupboard. If they don’t open when dry, gently crush pods and capsules to release the seed. After extracting the seed, clean off any surrounding material (chaff) attached to them, as this material could cause rot.

Place dry seed in labelled paper packets or envelopes in an airtight container with some desiccant to remove excess moisture. Suitable materials include calcium chloride (sold in DIY stores for use in dehumidifiers) or silica gel. Keep the container in a cool, dark place at an even temperature.

Saving wet seed

This is a more complicated process. Most seed is ripe when the surrounding fruit is ripe and ready to eat eg. tomatoes. However seeds of the cucurbit family (cucumbers, courgettes, squashes) should be harvested at maturity and then left in a warm dry place for a few weeks before being processed to allow their seeds to mature

Seed from most fleshy fruits and berries can be simply mashed in a fine sieve and then the pulp rinsed away in cold water. Then the seed left to dry for a few days on paper towels.

However some wet-seeded crops (particularly tomatoes and cucumbers) have a germination-inhibiting enzyme in a jelly around their seeds, which needs to be removed through a process of fermentation:

1. Remove the seeds, juice and pulp and put into a jar.

2. Leave the mixture to ferment for 2-3 days in a warm place (22°C is good) until mould forms on the top. This mould contains the germination inhibiting ‘jelly’ around the seeds, and this needs to be removed.

3. Top up the jar with fresh water and give it a good shake.

4. Pour off the pulp and mould making sure not to pour the seeds out too – the good ones should sink which is useful.

5. Top up with fresh water again, and repeat this process until the water is really clean.

6. Tip the seeds out into a sieve and then then spread them out to dry in a single layer on a non-porous surface until thoroughly dry.

7. Place dry seed in labelled paper packets or envelopes in an airtight container with some desiccant to remove excess moisture. Suitable materials include calcium chloride (sold in DIY stores for use in dehumidifiers) or silica gel. Keep the container in a cool, dark place at an even temperature.

Click on this link to the file to print the seed packet. Then follow the instructions.

Label with the type and variety of seed, the date collected and any special information for sowing .

Thanks to Amanda Abbitt for her expertise, and Gwen Nabbs for finding the seed packet template.