Seed saving from many vegetable and fruit varieties is incredibly easy, and tomatoes are a great place to start. This is because the flower pollinates itself as it opens, so crosses are rare. Not impossible, however, and it’s always best to err on the side of caution any time you want to be sure that the variety will breed true.
Lots of the tomato seeds that can be puchased at your local garden centre are ‘F1’ varieties, meaning they’re a ‘filial’ cross between two different parent plants. Avoid saving seeds from these, as they will not breed true – and if you’re saving seeds in order to preserve particular characteristics that you like, it’s a waste of time.
Decide which plants you’ll be seed saving from
First, and fairly obviously, make sure you’re saving seeds from your favourite varieties! The plants should be disease-free, and the fruits themselves slightly over-ripe. The actual method for saving tomato seeds varies according to who you ask. There are basically two methods, fermentation (which can save loads of seeds at a time) and the more straightforward drying, which is fine if you want to save just a few seeds.
There is a gelatinous coating on the seeds that contains chemicals which slow or even prevent germination. It can also harbour harmful bacteria which will then affect the seedling. This can be removed by fermentation.
To do this, slice a tomato around its equator and scoop the seeds out into a water-filled jar. Leave them there for at least a day. Some say you should leave the mix for 5 or 6 days, until a mouldy scum has developed on the surface, then pour it off, rinse the seeds, and dry them. Others say this is far too long and may result in diseases (canker, for one) spreading to the seeds themselves. In fact, a single day is enough to soften the grip of the coating, and a firm rinse in a fine sieve will then remove it altogether.
Don’t bother to hang on to any seeds which are still floating, as they won’t germinate. Pour them off with the excess water.
However long you leave the seeds to ferment, rinse them several times to ensure all remnants of the coating have been removed. Then spread them out onto a paper towel or plate until they’re completely dry.
This method is much less work than the above, and in just a few minutes you can save enough seeds to fill next year’s garden with tomato plants.
Cut the fruit open, as described above, and scoop a few seeds out onto a paper towel. Squeeze a seed firmly in the towel, and the coating…pops right off. The seed can then be laid out on another towel, or paper plate, as when using the fermentation method.
Some people may worry that this method, while removing the coating, won’t remove the harmful bacteria. In fact this doesn’t seem to be the case.
Tomato seeds remain viable for 2 to 3 years if stored properly, which means completely dry in a cool, dark place. If you have a favourite open pollinated tomato, and especially if it’s an heirloom type which may be difficult or impossible to find again, do yourself a favour and save some seeds. Then you’ll be able to enjoy them every year!