Saving seeds means harvesting seed from your own vegetable plants, drying it properly and storing it cool, dark and dry for the next season. Start with easy self-pollinators such as tomato, bean, pea and lettuce, and always choose open-pollinated varieties rather than F1 hybrids. Let the seed ripen fully on the plant, dry it bone dry and store it in a paper envelope or glass jar with the name and the year on it. Stored well, a lot of vegetable seed stays viable for three to six years.
Sound like something for you? Good. In this article I will walk you through the whole process: why you would bother, which varieties work and which do not, how to prevent crossing, how to go about it for each crop, and how to keep your seed good for years. Concrete, with rules of thumb and a couple of handy tables.
Why save your own seed?
There are three good reasons to save seed yourself.
It is free. One ripe tomato gives you enough seed for dozens of plants. One lettuce that bolts hands you hundreds of seeds. So you never have to buy another packet every spring.
You get locally adapted varieties. If you save seed from your strongest, healthiest plants every year, you are automatically selecting for plants that do well in your soil and your climate. After a few seasons you have a strain that suits your garden better than anything you can buy in a shop.
You are self-sufficient. You are not dependent on whatever the seed trade happens to stock that year. And you keep old, unusual varieties alive that would otherwise disappear.
There is one important condition attached, and it decides whether this works or fails: the variety.
F1 hybrid or open-pollinated? This is the most important thing to know
This is the trap most beginners fall into, so read this bit properly.
On seed packets and plant labels you will roughly find two kinds of varieties: open-pollinated varieties and F1 hybrids.
An open-pollinated variety came about the classic way, through crossing and selection. The key feature: if you harvest seed and sow it again, the offspring are virtually identical to the parent plant. The variety stays “true” (source: De Bolster, organic seeds). Exactly what you want when you save your own seed.
An F1 hybrid is something else entirely. F1 stands for “Filius primus”, the first generation after a cross between two different parent lines. That first generation is very uniform and often extra vigorous. But, and this is crucial: if you save seed from an F1 plant, you do not get a copy of that plant back. The next generation (the F2) breaks apart again into all sorts of different types, with variable looks and variable quality (source: De Bolster; Eosta). So you have no idea what you will get, and usually it is a disappointment.
The rule of thumb is simple: if the packet or label says “F1” or “F1 hybrid”, there is no point saving seed. Choose varieties without that marking, and you can often spot them by terms such as “open-pollinated” or “organic open-pollinated”. Not sure? Check the original seed packet or ask the seed supplier.
Preventing crossing: self-pollinators versus cross-pollinators
Even with an open-pollinated variety, something can still go wrong: crossing with another variety of the same crop. Whether that is a problem depends on how the plant pollinates.
Self-pollinators pollinate themselves inside their own flower, often before the flower even opens. The chance of crossing with another variety is very small. These are the easiest crops to start with. Tomato, lettuce, bean and pea belong to this group (source: Zadenbibliotheek Nederland). Here you can happily grow several varieties side by side and still save true-to-type seed.
Cross-pollinators are pollinated by insects or by wind, with pollen from another plant. If another variety of the same crop is flowering nearby, they cross easily. Think of pumpkin and courgette, all the brassicas, beetroot, carrot and sweetcorn. Here you only get true-to-type seed if you let just one variety of that crop flower, or if you isolate the varieties.
You can isolate in a few ways:
- Spatial isolation: keeping enough distance between two varieties. With pumpkin and courgette you are quickly talking hundreds of metres, far more than an ordinary garden allows, so in practice you grow just one variety per species.
- Physical screening: covering female flowers with fine insect mesh and pollinating by hand.
- Timing isolation: letting varieties flower at different moments.
An extra reason to be careful with pumpkin and courgette: crossed fruits can contain more cucurbitacins, which makes them bitter and mildly toxic (source: Diana’s mooie moestuin). So always taste a small piece of a home-saved pumpkin or courgette before you cook a whole meal with it. Bitter? Do not eat it.
Practical rule of thumb: if you want to start without any fuss, stick to self-pollinators. Tomato, bean, pea and lettuce will give you true-to-type seed almost every time, even with several varieties standing next to each other.
Overview: the method per crop at a glance
| Crop | Pollination | Difficulty | Method in short |
|---|---|---|---|
| Tomato | Self-pollinator | Easy | Ripe fruit, ferment seed with its gel, dry |
| Bean | Self-pollinator | Easy | Pods bone dry on the plant, shell them |
| Pea | Self-pollinator | Easy | Pods bone dry on the plant, shell them |
| Lettuce | Self-pollinator | Easy | Let it bolt, harvest the fluffy seed heads |
| Pepper/chilli | Self-pollinator | Easy | Fully ripe fruit, take the seed out dry |
| Courgette | Cross-pollinator | Moderate | Let a fruit grow on until hard, scoop out the seed |
| Pumpkin | Cross-pollinator | Moderate | Fully ripe fruit, scoop out the seed and dry it |
| Cabbage | Cross-pollinator | Hard | Overwinter, let it flower, harvest the seed pods |
| Beetroot, carrot | Cross-pollinator | Hard | Biennial, overwinter, let it flower |
Below I work out the most important crops in more detail, from easy to hard.
Saving tomato seed: fermenting step by step
Tomato is the most popular crop to start with, and rightly so. There is just one extra step involved: fermenting.
Why ferment? Every tomato seed sits inside a jelly-like coating. That gel contains substances that inhibit germination, so the seeds do not sprout inside the fruit. In nature that layer disappears as the fruit rots away. By letting the seeds ferment for a few days you imitate that rotting process: the gel layer dissolves, and you remove disease organisms along with it. The result is cleaner seed that germinates better and stays viable longer (source: Zadenbibliotheek Nederland).
Here is how you do it:
- Pick one or more fully ripe, healthy tomatoes from an open-pollinated variety.
- Cut them in half and spoon out the seed with its gel into a tub or a glass.
- Add a splash of water.
- Put the tub somewhere warm and light, on a windowsill for instance, but not in bright sunlight and not on a radiator. Put a lid on it if the smell bothers you.
- Leave it for roughly 3 to 5 days and stir now and then. A layer of mould forms on top, which is part of the process (source: Zadenbibliotheek Nederland; De Tuin op Tafel).
- Top it up with plenty of water. Good, heavy seeds sink to the bottom. Empty seeds, skins and mould float. Carefully pour off the floating part.
- Rinse the good seeds clean in a fine sieve.
- Spread them out on baking paper or a plate (not on kitchen paper, they stick to it) and let them dry thoroughly.
Done. Kept dry and cool, tomato seed stays viable for years, up to about four to six (source: mooiemoestuin.nl; De Tuin op Tafel).
Bean and pea: let them ripen and shell them
This is possibly the easiest seed there is, because the bean or pea is the seed.
Simply leave a few pods on the plant and do not pick them to eat. Wait until the pods are brown, paper dry and hard, and the seeds rattle when you shake the pod. Then pick them on a dry day.
Shell the pods and take the seeds out. Let them dry on a bit longer indoors afterwards, because there is often still some moisture in them. Only put them away once they are so hard that you cannot dent them with your fingernail.
Watch out: pick too early, while the pods are still green, and the seed is not fully formed, so it germinates badly or not at all. Patience, then.
Lettuce: let it bolt
You normally eat lettuce before it flowers, but for seed you deliberately leave a few plants standing.
Let a few nice, healthy lettuce plants bolt: they then form a long flowering stem with small flowers. After flowering, fluffy seeds appear, a bit like on a dandelion. Those fluffy heads do not all appear at the same time.
Harvest the ripe heads regularly, or cut off the whole flowering stem once most of it is ripe and let it dry on indoors over a tub or a bag. Then rub the seeds out and blow the light fluff away. One lettuce plant gives you an enormous amount of seed (source: Stadstuinieren).
Pepper and chilli: just harvest them dry
Peppers and chillies are beautifully simple. No fermenting and no water involved.
Let the fruit ripen fully on the plant, so often redder (or yellower) than you would eat it. Cut it open, take the seeds out and lay them on a plate or on baking paper to dry. That is all there is to it.
Small tip for hot chillies: wear gloves when you take the seeds out, because the heat sits precisely around the seed membranes.
Courgette and pumpkin: let them grow on until hard
This is where ripeness really matters, because ready to eat is not the same as ready for seed.
You eat a courgette young and soft, but at that point the seed is nowhere near finished. For seed you let one fruit grow on completely until it is big, hard and a dull yellow, and the skin can no longer be dented with your fingernail. The same goes for cucumber: let one turn yellow and fat. With pumpkin it is easier, because you only eat those when they are ripe anyway.
Cut the ripe fruit open, scoop out the seeds, rinse the flesh off in a sieve and lay the seeds out to dry. For pumpkin and courgette, remember the crossing issue (see above) and preferably grow just one variety per species.
Ripeness: nearly always later than eating ripe
The biggest mistake in seed saving is harvesting too early. Remember this rule:
Seed is only ready when it is fully ripe, and that is often much later than the moment you would eat the vegetable.
- Courgette and cucumber: let them grow on until yellow and hard.
- Bean and pea: pods bone dry, seeds rattling.
- Lettuce: only harvest once the fluffy heads form after flowering.
- Tomato and pepper: fully ripe, a little past eating ripe is perfectly fine.
Unripe seed is not fully formed and germinates poorly or not at all. When in doubt, leave it hanging longer.
Drying: bone dry, otherwise it goes mouldy
Drying properly is the most important step for a long storage life. Seed that is not dry enough goes mouldy or heats up, and loses its viability.
Spread your cleaned seed out on a plate, on baking paper or in a fine sieve, somewhere airy and out of the sun. Stir it around now and then so everything dries evenly. Count on a good one to two weeks, and longer in damp weather. The rule of thumb is: too long beats too short (source: Stadstuinieren).
How do you test whether it is dry enough? A good test: a genuinely dry bean or pea cannot be dented with your fingernail and snaps when you try to bend it in half, it does not fold. Flat seed such as tomato or pepper should feel crisply dry and should no longer stick together. Not sure? Leave it out for another few days.
Storing: cool, dark, dry
Are your seeds bone dry? Then storage comes down to three words: cool, dark and dry (source: mooiemoestuin.nl; Gardeners’ World). Those are the conditions in which seed holds on to its viability longest.
Practical tips:
- Packaging: paper envelopes breathe and let residual moisture escape, handy if you are not 100 per cent sure about the dryness. Glass jars seal airtight and keep moisture out, ideal for bone dry seed. A much-used combination: seed in a paper envelope, and that envelope inside a sealed (freezer) box or jar with a sachet of silica gel to absorb moisture.
- Always label with the name of the crop, the variety and the year. Without a label you will not know what is what in a few months, and that is the single most common mistake.
- Location: a cool, dark cupboard, for example against a north wall, works fine. The fridge keeps a constant low temperature and extends storage life further still. The freezer is an option too, but only if the seed is truly bone dry and airtight, otherwise moisture damages it.
- Avoid temperature swings and damp. A shed that alternately freezes and thaws is less suitable than a stable cupboard indoors.
Remember the core of it: dry and consistently cool. That is why big seed banks such as the one on Svalbard store seed at around -18 °C in extremely dry conditions (source: Stadstuinieren). At home you do not need to go that far, but the direction is the same.
How long does seed stay viable?
Seed slowly loses its viability. How long it stays good varies a lot per crop. Some seed is better bought fresh every year (onion, parsnip), other seed keeps for years. The table below gives guide figures for good, dry storage.
| Crop | Keeps (years) |
|---|---|
| Onion, leek | 1 to 2 |
| Parsnip | 1 |
| Parsley | 2 |
| Carrot | 3 to 4 |
| Bean, pea | 3 |
| Lettuce | 3 to 4 |
| Pepper, chilli | 3 to 4 |
| Sweetcorn | 2 |
| Beetroot, chard | 4 to 5 |
| Cabbage, broccoli, cauliflower | 4 |
| Spinach | 4 to 5 |
| Tomato | 4 to 6 |
| Cucumber | 4 to 5 |
| Courgette, pumpkin | 5 |
(source: mooiemoestuin.nl; Gardeners’ World; De Tuin op Tafel)
These numbers are guidelines. Badly stored seed is finished much sooner, well stored seed can last longer. Viability also drops gradually within a single year, so old seed often gives a slightly thinner stand.
Do the germination test: unsure about old seed?
Not sure whether an old packet still has anything in it? Then do a germination test at home, it saves you a failed sowing.
- Lay 10 seeds on a damp piece of kitchen paper.
- Fold the paper over and put it in a sealed bag or box (or cover it with cling film) so it stays damp.
- Put it somewhere warm and keep the paper damp.
- Check every few days. Count on 1 to 2 weeks (source: Gardeners’ World; mooiemoestuin.nl).
Then count how many of the 10 have germinated. If 8 come up, that is a solid germination rate of around 80 per cent and you can sow as normal. If only 3 or 4 come up, sow more thickly to make up for the low rate, or buy fresh. Nothing at all after two weeks? Bin the seed and start with new.
The 5 most common mistakes
- Saving seed from an F1 hybrid. You get unpredictable offspring. Choose open-pollinated varieties.
- Harvesting too early. Unripe seed germinates badly. Let it ripen fully on the plant, usually later than eating ripe.
- Putting it away not dry enough. Damp seed goes mouldy. Dry it bone dry and test it.
- No label. Without a name and a year you lose track. Write it on straight away.
- The wrong storage spot. Warm, damp or variable conditions shorten storage life considerably. Cool, dark and dry is the standard.
Frequently asked questions
Can I save seed from a supermarket tomato?
Those are often F1 hybrids, whose offspring are unpredictable. You can try it as an experiment, but you do not know what you will get. For a reliable result, buy open-pollinated varieties once and save your own seed from those afterwards.
Why does tomato seed need fermenting and pepper seed does not?
Tomato seed sits in a jelly-like coating that inhibits germination and which fermenting removes. Pepper and chilli seed sits dry inside the fruit, so you can simply take it out and dry it (source: Zadenbibliotheek Nederland).
How do I know if my seed is dry enough to store?
It has to be bone dry. At that point a bean or pea can no longer be dented with your fingernail and snaps rather than folds. Flat seed feels crisp and no longer sticks together. When in doubt, dry it longer.
Can seed go in the fridge or freezer?
Yes, as long as it is genuinely bone dry and airtight. A cold, constant temperature extends storage life. Moisture in the packaging is what does the damage, so add silica gel if you want to be safe.
Which crops are easiest to start with?
Self-pollinators: tomato, bean, pea and lettuce. They give true-to-type seed almost every time, even if you grow several varieties side by side.
Why did my home-saved courgette turn bitter?
It has probably crossed with another courgette or a pumpkin, which pushes up the cucurbitacin level. That makes the fruit bitter and mildly toxic. Always taste a small piece, and do not eat it if it tastes bitter (source: Diana’s mooie moestuin).
Getting started
Saving seed is not complicated science. Start small this season: let a few nice tomatoes go fully ripe, let a few beans ripen on the plant and let one lettuce bolt. Choose open-pollinated varieties, let everything ripen properly, dry it bone dry and store it cool, dark and dry with a neat label on it. Next spring you sow your own harvest, and that feels good.
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