Never buy vegetable seed again! How to save money by harvesting this year’s beans, lettuces and tomatoes

Every year, our gardens and allotments yield a huge crop of seed, yet most of us let it go to waste. Here’s how to save it – and a small fortune

If you are any kind of gardener, I bet you have a drawer filled with half-empty packets of vegetable and herb seeds. It is easy to get stuck in a cycle of buying new seeds each growing season because you have forgotten you already had some, or you are not sure what is out of date. We all do it, but it is possible to break the habit – and now is the time.

Collecting your own seeds makes sense in many ways. You save money. You avoid all the embodied energy in bought seeds: the transportation, the colour printing, those silver foil packs that can’t be recycled. As long as you dry your seeds properly, so they will store well, you might also find you get much better germination because they are fresh. You will also have something to barter with. If you didn’t get the hang of saving chilli seeds, say, but have plenty of lettuce (and a single lettuce can produce more than 10,000 seeds), there will be a gardener somewhere who is willing to swap. Look out for local Seedy Sunday events, where seed savers come together in late winter or spring to do just that.

Perhaps the greatest joy of saving your own seeds is that you can select for plants that thrive in your garden. Don’t bother collecting any from plants that didn’t do well or went to seed early – that would be selecting for early bolting or weak genes. But every time you save seeds from a plant that excelled, you are slowly creating plants ever more perfectly suited to you, your soil and your gardening style. If a certain tomato does well under your haphazard watering regimen, or a bean thrives in your poor soil, that is something to celebrate and perpetuate. This is called “landrace gardening” and allows seeds to adapt to place.

When you save those seeds time and again, you are making an investment for future gardeners, too. Think of it like this: you got here because your ancestor saved you some seeds – now, it’s your turn.

You will need to collect your seeds on a dry day: have a container handy, as seedheads can be brittle and all your bounty may be lost if you don’t collect the seeds over something. You might then need to spread them out, so they can continue to dry indoors. Once bone dry, label and store somewhere dry and cool – not the windowsill or anywhere near the kettle. Moisture is the enemy.

Will everything give you usable seeds? Not quite, especially when you are just starting out. If collected and stored properly, any seed will germinate, but look out for “F1 hybrid” on the original seed packets, usually after the variety name. These plants were created by crossing two different parent varieties in strictly controlled conditions, which means their offspring will not have the same characteristics as the original plant you grew. It doesn’t really make sense to save seeds from F1 hybrids, as you have no idea what you will get.

Instead, you want to save from “open-pollinated” varieties – where pollination is handled by insects or the wind. Ideally, you should take seeds from several plants of the same variety, because each one will vary slightly in appearance, harvest time, hardiness, slug resistance and other characteristics. You want all this variation because it boosts the potential for the plants to adapt to a range of conditions.

However, many vegetables are so promiscuous that if, for example, you save the seed of your delicious, sweet courgette and Sid down the road is growing mammoth marrows with which to storm the horticulture show, your lovely courgettes may get Sid’s bound-to-be-flavourless but ginormous genes in the mix. This may make for something brilliant, but it is more likely to make for something watery and less flavoursome.

In order to keep varieties true, you might need to learn how to isolate plants from the pollinators. Sometimes, that is about distance, or even hand-pollinating the plants. Alternatively, let the pollination dice roll and start the journey of creating a new variety, but understand that there may be many flavour failures ahead before you land on the perfect mix.

Thankfully, there are plants that won’t cross-pollinate; they are all good starting points to learn the ropes and entice you to start breeding your own vegetables and herbs. Here are some of the easiest seeds to save.

Tomatoes are a doddle to save seeds from, because they tend to stay true to type (ie the offspring will have the same characteristics as the parent) and they self-fertilise, meaning if you grow 10 varieties it is very unlikely they will cross with one another.

Collect fully ripe tomatoes, cut the fruit in half and scoop out the seed and surrounding gel; eat the rest of the tomato. Put the seed and gel into a glass or jam jar and label it. If there is not enough gel, add a little bit of water – just enough to swirl it around; a teaspoon or so. Cover the glass with kitchen paper or cloth and leave on a warm windowsill. It will start to ferment and probably smell quite bad. When white mould starts to appear, the gel has broken down enough – leave it too long and the seeds will start to germinate. At about 20C, this will take three days.

Remove the mould and pour the remaining mixture into a sieve. Wash off any remaining debris. Place the seeds on a plate (not on kitchen paper, to which they will stick). The seed tends to clump together, so break them up during drying, so you have individual seeds. Once fully dry, store your seeds somewhere dark, cool and dry.

Saving seeds from French beans is very easy. It doesn’t matter if you have grown different varieties, too, as they don’t readily hybridise with each other; just a few metres between plants is enough to make sure varieties stay true.

Wait till the pods are yellow, then, if necessary, bring them indoors to dry further. Once they rattle, remove the seed. The seed is dry enough if you can’t leave an indentation on the skin with your thumbnail. If the seeds need to dry more, spread over a plate and leave until ready.

Runners are much more promiscuous than French beans and will readily cross with anything you or your neighbours are growing nearby – you need to separate varieties by at least 100 metres. Either accept that you will get a hybrid or, if there are no other gardeners nearby, grow a single variety and collect from that. I grow greek gigantes one year and black coat the next; each year gives me enough seed to make this system work. French and runner beans are different species, so they won’t cross from natural pollination.

Peas are the easiest of the lot – you need only a few plants and there is little chance of cross-pollination. Those pods that you missed when harvesting, and are now browning and turning parchment-like, are your free seed for next year. If the weather is dry, leave them on the plant to dry completely; if not, bring the pods in. Shelling is easy enough; if you have loads, put them in an old pillow case and whack it against the wall. You can dry the seeds further if they need it.

Throw out any that are damaged, discoloured or have small holes in them. These have been beset by pea moths, which are now pupating in the soil somewhere; the seed damage usually makes for bad germination.

Lettuce is an old favourite of mine. Just one or two plants can give you more than enough for several years and, as they self-pollinate, you don’t have to worry too much about hybridisation. But you are dependent on a good summer, as the seedheads can go mouldy in wet weather.

The flowers don’t come out all at once, so you have to go out every few days and collect the seeds from white plumes of thistle-like seedheads. I find its easiest to go out with a container and shake the seedheads to further sort and clean indoors. If the weather is wet, you are better off uprooting the whole plant and hanging it upside down inside to dry; put a paper bag over the seedheads and save what you can. Gently rub the seedhead into a sieve and shake it; the seeds will fall to the bottom and the fluff will rise on top, making it easy to pick off.

Parsley, dill and herb fennel are in the carrot family, Apiaceae, and give you a huge abundance of seeds from just a few plants. It’s one family where fresh seeds make a huge difference, so if you have ever found any of these herbs hard to germinate from bought seed, you will be surprised to see your own seeds germinate quickly and readily.

Dill, being annual, will give you plenty of seeds by the end of the summer; collect it on a warm day when it is brown and bring it indoors to dry further. Fennel plants are perennial, but the seeds appear at the same time as dill, towards the end of the summer. The seedhead tends to shatter easily, so you have to keep your eye out – the minute it is buff-coloured, collect the seeds and dry off further inside. Dill and fennel will readily self-seed about the garden, so if you don’t have time to collect seeds, let the garden take care of it.

Parsley will hybridise with other parsley plants, so if you are growing flat-leaf and curly you will get something in between. Parsley is biennial, its two-year lifecycle meaning it will need to overwinter to set seeds the next summer. I think it is a very pretty flowerhead and I love to leave it to live out its full life in the garden.

Flat-leaf parsley is not always winter-hardy, though, so if you are anywhere less than sheltered, it makes sense to dig and pot up plants to overwinter in a greenhouse, if you can.

Basil comes in many varieties. If you have grown different types and they are already flowering, the insects will have cross-pollinated them and thus anything saved will now be a mix. There might be something wonderful in there, there might not. It’s a gamble, but one worth taking.

If you want to keep the varieties true and they have not yet flowered, choose one you want to keep seeds from, let it flower and pick the flower spikes off all the other varieties. Once the flowers have withered on your seed-saving plants, you can let the others flower (they are beloved by pollinators). When your target flower spikes have gone completely brown, snip them off and bring them indoors to process the seeds. They rather cling to the seedhead, but are easy enough to rub off on to a plate.