Old Tomato Seeds: How Long Do They Last & How to Revive Them?

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Nothing makes me happier than purchasing more and more packets of seeds. Looking through all those colourful sachets showing vegetables and flowers at their best, with new and exciting varieties that promise tastier, more reliable crops being bred all the time. 

‘Do I really need that packet of seed?’ Is a question I should ask myself more often, but I simply can’t resist the promise of things to come. And generally, a packet of seed is much cheaper than purchasing a nursery-grown seedling or young plant so it’s a cost-effective way of creating your own vegetable garden. 

But if you’re like me, you’ll struggle to get through the sheer amount of seed packets you buy, some of which are very generous with their quantities and you’ll always end up with plenty left over for next year.

So in this article, we’re going to investigate just how old is too old – namely, just how long do tomato seeds last?

Learning (the hard way) how to propagate old tomato seed

My mum gave me a packet of the highly reliable Ailsa Craig tomato seed that she had grown in the garden when I was young. These seeds were around fifteen years old but I was so determined to germinate these archaic seeds that I tried everything. I soaked some in warm water, cold water, marinated them in wet paper tissue, I even soaked some in a mild tea solution as I read this could help with softening the seed casing.

Needless to say, I wasn’t successful, the seed packet had lived in the shed for 15 years and was exposed to all the elements – the seeds had simply stopped being viable.

If you look at the back of any new seed packet it will have a ‘packed in’ year and a ‘sow by year‘, very much like fresh produce has ‘best before’ dates. But if you’re sensitive to food waste you’ll know these are mainly just for the supermarkets’ benefit (I personally find that the reduced sections always have the best stuff anyway, it’s ripe, tasty and ready to eat!).

Your seed packet will normally give you 2-3 years between these dates as a guide for when your seeds will be at their best. 

How long can you keep tomato seeds before they won’t germinate?

The Millennium Seed Bank at Kew Gardens is home to 2.3 billion seeds and is the most diverse wild plant seed resource on Earth, ensuring that seeds stored today will be saved for generations to come.

“Every 1% we reduce a seed’s moisture content doubles its life span. Our initial drying phase increases a seed’s life 40 times over. This can take between two weeks and six months…After which, they are placed in labelled jars and stored in our sub-zero chambers. These collections are curated to international gene-bank standards”

I’m not suggesting that you go to the same lengths as the MSB to store your seeds but here are some helpful tips that might help you understand how long they will last and how to get the best longevity out of them.

How to store tomato seeds to prolong viability

I currently have five-year-old tomato seed which still reliably germinates every year without any additional help so it’s not always the age of the seed to be concerned with, it’s how you store them.

The best possible way to take care of your tomato seed is to store them in a cool, dry, dark and stable environment. Mine are stored in my Grandma’s old fold-out toolbox which I honestly find hard to lift because it’s so full of reduced and expired seed. 

We keep our seeds inside the house, in a cold room that doesn’t have a radiator. A seed is simply an embryo of a plant with a small amount of food encased in a hard shell for protection. Given the right conditions, warmth, water, light this seed will germinate. Storing your tomato seed correctly will suspend it in a dormant state until it is given what it needs to start life. 

People often think that you need to store your seed in an air-tight container. This can be a good way to prolong your seeds, however, it may not always be the right place. Any moisture trapped can cause your seeds to grow mould, especially when they are tightly packed and may not have enough airflow between the seeds. 

When you open a new packet of seeds they will often be packed inside a small foil sachet inside the packet to help control moisture in the atmosphere. Once opened make sure you reseal your packet to keep them safe and fresh for another growing year.

How to revive old tomato seeds

If you’re attempting to revive old tomato seeds, there are some popular ways in which gardeners help the process along:

Testing the viability of old tomato seeds

First of all, if you’re interested in testing the viability of your seed beforehand, pop your seeds into a small glass of water, give it a gentle stir and leave for 20 minutes. Some seeds will sink to the bottom, some will float to the top. ‘

General opinion says that these floating seeds are not viable but, having done this test with tomato seeds among others, I have found that it’s not always accurate. Floating seeds can also germinate, it may just show which seeds are denser. But if you have a generous amount of old seed it could be an interesting experiment of your own. My gut would always go with sowing them all though, because it can’t hurt to try.

Using a heated propagator to revive old tomato seed

When reviving old seeds we can’t forget the importance of a perfect germination environment. In my most desperate of times, I have found myself praying to the germination gods, this gives mixed results… The most reliable way is to get your hands on a heated propagator. This little bit of kit will bring you a lot of joy as you watch all your seedlings emerge, and is especially beneficial for tomato, pepper, chilli and aubergine seeds – those that like a warm start to life.

Pre-soaking old tomato seeds can improve germination

I mentioned earlier that pre-soaking your seeds in water can help soften the seed casing. This should be overnight at the most, as you don’t want to wet your seed too much that it rots. 

Most years I will make a cosy wet paper tissue duvet for some special saved tomato seeds that I simply have to germinate (like the five-year-old Zlatava we picked up at Chelsea Flower Show). I will re-moisten the tissue with warm water when it has dried out a little and take an occasional peek to see the progress. 

Soaking your seeds in a very weak solution of water and tea or coffee is a way of mimicking nature. These little seeds are designed to be resilient enough to withstand the trials and rigours of the natural world, so some think that a slightly acidic water solution like that of your morning brew can emulate a seed having been digested and travelling through an animal, which would begin to break down the seed casing before germination.

Conclusion

Hopefully, some of these tips may help you prolong the life of your tomato seeds and revive some old packets that you just can’t let go of. The chances of your 100-year-old tomato seeds germinating are slim, but if you’re looking for inspiration, this determined kindred spirit has had some very interesting results with some 87 year old seed, so there’s always a chance!