Saving Your Own Vegetable Seed

Start with annual, self-pollinating, open-pollinated crops: peas, beans, tomatoes and lettuce. Seed saving runs on its own calendar: a pea worth eating is far too immature to store, and seed is ready only when the pod has gone papery and brown, weeks after the last worthwhile picking. Biennials such as carrots and onions give no seed until their second year, and F1The first-generation offspring of two specific, deliberately chosen parent plants, bred for a predictable, uniform result but not worth saving seed from. Full definition → hybrids do not come true.

Which crops to start with

The realistic starting point is annual, self-pollinating, open-pollinated crops: varieties that breed naturally, so the seed reliably reproduces the parent because there is little risk of cross-pollinationPollen moving from one plant to a different, compatible variety, needed for fruit to set on any variety that isn't self-fertile. Full definition → by a different variety nearby. Peas, French and runner beans, tomatoes and lettuce all fit, and all are practical for a first attempt. Save from healthy, vigorous plants, and from several plants rather than one or two, so the variety keeps a broad genetic base.

Harder are the cross-pollinating crops, such as squash and pumpkins, courgettes, brassicasThe cabbage family: cabbage, kale, broccoli, cauliflower, Brussels sprouts, kohlrabi, swede, turnip and more, sharing the same pests, diseases and rotation rules. Full definition → and most alliums, which need isolation or hand-pollination to keep seed pure. Two courgette varieties flowering near each other can produce seed that throws offspring nothing like either parent.

Some seed will not work at all: F1 hybrid seed does not come true. An F1 is a one-off cross between two parent lines, and seed saved from it gives variable results, not the plant you grew. The F1 label on the packet is the giveaway. Only open-pollinated varieties are worth saving from.

Biennials: harder, especially in Scotland

A carrot, onion or cabbage grown for the plate is harvested exactly when a seed-saver would need to leave it alone, because its energy has gone into the root or head. Seed appears only in year two, after the plant has overwintered and flowered. The best plants are left in the ground, or lifted and replanted in spring, to overwinter, then flower and ripen seed through their second summer. Parsnips, leeks and brassicas follow the same pattern.

A biennial seed crop must flower, be pollinated and ripen its seed before the first hard autumn frost, which is a tighter finish in Scotland's shorter, cooler season than in southern England. First autumn frost is typically late October on lowland ground and mid-to-late September on upland (see Scottish frost dates). Peas, beans, tomatoes and lettuce complete flowering and ripening inside one season without surviving a winter.

Cross-pollination and keeping a variety pure

For outbreeders, isolation distance is how far apart two varieties of the same crop must be so their flowers do not cross. It differs with plant species.

On an ordinary allotment or back garden a mile is beyond most growers, so the practical fallback for brassicas is timing and barriers. Grow only one variety of each brassica species, such as one cabbage, kale or cauliflower (Brassica oleracea), into its second year, or stagger the sowing so flowering does not overlap, which is harder in Britain's short season. Otherwise put each variety inside a fleece or fine mesh cage and introduce pollinators by hand or with flies. Flies pollinate around 40 per cent of brassica flowers while bees do much better, so caged plants may set less seed, and cool, wet flowering weather may ground bees more than flies, and hand-pollination is the workaround. Allow at least 20 plants of the variety to mature, since brassicas are outbreeders.

Remove ("rogue out") any plant that is diseased, off-type or has boltedA plant switching early into flowering and seed production, usually triggered by stress, after which leaves, roots or bulbs turn bitter or unusable. Full page → early as soon as it is spotted, so its traits do not reach next year's seed. Wild brassicas, including oilseed rape, can also cross with brassica crops.

Squash and pumpkins have separate male and female flowers on the same plant, so hand-pollination is the reliable option on a small plot: pick a freshly opened male flower, strip its petals and dab the pollen onto the female flower's stigma, then tape or tie the female flower shut for a day to keep bees from adding other pollen. The female flower has a small swelling, the immature fruit, behind its petals.

Tomatoes rarely need any of this. Most have perfect, self-pollinating flowers. Some varieties have a stigma that can collect pollen from similar varieties, so for safety grow just one of that type a year.

Harvesting: let it mature on the plant

Do not cut anything early. Collect on a dry day to limit fungal rot, once the seed head, pod or fruit has ripened in place; a colour change from green to brown, black or red is usually the signal. For peas and beans, leave pods on the plant until they are papery brown and rattle when shaken. Seed development stops once the stem is cut, so green pods do not finish ripening off the plant. If weather threatens the crop, pull whole plants and hang them somewhere dry and airy, such as a shed roof or greenhouse rafters, to finish drying under cover.

Wet-processing (tomatoes and other fleshy fruit)

Tomato seed sits in a gel coating that inhibits germinationA seed sprouting: breaking dormancy and putting out its first root and shoot, given the right warmth and moisture. Full definition →, so ferment it off rather than just rinsing. Scoop the seed and pulp into a jar of water and leave it somewhere warm for about three days, stirring occasionally; a light mould often forms and the gel breaks down. Rinse through a sieve, discarding anything that floats, since viable seed sinks, then spread it on a paper towel to dry.

Dry-processing (pods and seed heads)

For peas, beans, lettuce and most seed-head crops, once the pod or head is fully dry it can be threshed by hand or in a sack. Winnow by pouring seed between containers in a breeze, or blow the chaff away from a tea strainer or sieve, so the lighter chaff goes and the heavier seed drops.

Drying: the step Scotland makes harder

Everything above assumes a proper finish-drying stage before storage. In a damp Scottish garden it takes longer and matters more, because seed stored even slightly damp is far more likely to mould. Lay seed out to dry on a greenhouse bench, warm windowsill or in an airing cupboard. Judge dryness by more than the calendar:

• Pods and seed heads should be crisp and papery, not leathery, and pea and bean pods should rattle when shaken; a dull, silent pod usually means soft seed.
• Fermented tomato-type seed should feel hard and separate, not tacky or squashy, after roughly one to two weeks air-drying in a warm, bright, not hot spot.
• If in doubt, extend the drying rather than store early: a few extra days costs nothing, while mould in a sealed envelope loses the batch.

Do not speed it up with an oven or dehydrator: strong heat is likely to kill viability, particularly in peas and beans.

Storage: envelopes first, airtight second

Seed still finishing its drying belongs in breathable paper, an envelope or paper bag, never sealed plastic, because trapped moisture causes mould. Once it is completely dry, put labelled paper packets or envelopes in an airtight container with some desiccant such as silica gel or calcium chloride, and store it cool, dark and dry; a refrigerator at 5°C is recommended until sowing. Label each packet with variety and year when you store it, not later from memory.

How long saved seed stays viable

Viability depends on the crop, the seed's condition when stored and how long and how well it is stored, so treat any figure as a guide. Stored dry and cool, most seed remains viable for many years, though some crops are short-lived.

Parsnip is the standout exception: old seed germinates poorly, so buy or save fresh seed every year.

To check seed that has been stored a while, drop medium to large seed in a jar of water: viable seed sinks and dead seed floats. For small seed, or to be sure, fold ten seeds into a damp paper towel in a bag somewhere warm and check after a week or two; if fewer than about half germinate, buy fresh seed rather than rely on the batch.

Common questions

Sources