Why Save Your Own Bean Seeds

Beans are among the most rewarding crops to save seed from, and they sit at the easy end of the seed-saving spectrum. The plants are mostly self-pollinating, the pods dry down naturally on the stems, and the resulting seed is large enough to handle without tweezers or a magnifying glass. A single healthy runner bean plant left to mature will give you far more seed than you need for next year's row, leaving plenty to swap with allotment neighbours or tuck into a seed tin for the year after.

There is a satisfaction in it beyond the economics. Save seed from your best plants year after year and you gradually select for beans that crop well on your soil, in your particular corner of the country. That slow, patient adaptation is something no packet of bought seed can offer.

Choose the Right Plants and Pods

Selection starts long before the pods turn brown. Walk your rows through the season and mark the plants you want to keep.

• Pick plants that are healthy, vigorous and free of disease — anything with rust, chocolate spot or mosaic virus should be avoided entirely, as problems can pass through the seed.
• Favour plants that cropped early and heavily, with pods set low on the plant rather than only at the very top.
• If you are growing an F1 hybrid, don't bother saving seed — the offspring will be variable and often disappointing.
• Leave pods at the base or end of the row rather than picking them young for the kitchen. Runner beans left to swell become stringy and tough, but that matters not a jot when the seed is the goal.

Broad beans and runner beans cross-pollinate reasonably freely, so if you are keeping two varieties of either, either grow only one this season or keep them well apart with a tall crop or a hedgerow between. French beans, both dwarf and climbing, are far more self-contained and can usually be saved side by side without worry.

Letting the Pods Mature on the Plant

Patience is the whole game here. Leave the pods on the plant until they have turned from green to yellow, then to a brown or parchment colour, and finally to a dry, papery husk that rattles when you shake it. A French bean pod should snap rather than bend. Broad bean pods will darken to near-black.

In a decent September this happens neatly out in the garden. In a wet, grey autumn — which is more often the reality — the pods can start to mould before they finish drying. If the forecast is grim, lift the entire plant, roots and all, and hang it upside down in a dry, airy shed or garage. Tie a paper bag or an old tray underneath to catch any beans that drop, and give them a few weeks to finish drying indoors. Good airflow matters far more than warmth.

Shelling and Finishing the Drying

Once the pods are properly brittle, shelling is a pleasure. Twist or snap each pod open over a bowl and the beans should fall out cleanly, with none of the white, spongy material clinging to them. If a pod is still leathery or the beans resist coming free, put the whole lot back to dry for another week.

Spread the shelled beans in a single layer on a plate, tray or sheet of newspaper in a warm, airy room — an airing cupboard, a spare bedroom or a sunny windowsill out of direct glare. Leave them for a fortnight, turning them occasionally. The test is simple: press a bean with your thumbnail. A properly dry bean shatters or splits; one that is still damp will dent or squash. Discard any beans that are shrivelled, cracked, discoloured or holed, and keep only the plumpest, firmest specimens.

Storing Seed Through to Spring

Beans keep best in the dark, and they hate damp and warmth in equal measure. Glass jars with screw-top lids are ideal, as are paper envelopes or cotton bags kept inside a larger tin. Avoid plastic bags, which trap moisture and can encourage mould.

• Label every container with the variety and the year — you will not remember in April.
• Store somewhere cool, dark, dry and frost-free, ideally between 5°C and 10°C. A bedroom wardrobe or a cool pantry is better than a warm kitchen cupboard.
• If your storage spot is at all humid, add a small sachet of silica gel to the jar.
• Check for bruchid beetles — tiny round holes in the beans are the giveaway. If you spot any, pop the jar in the freezer for 48 hours to kill eggs and larvae before sealing it up again.

Stored this way, bean seed will germinate well for three to five years, so there is no need to save a fresh batch every single season.

Checking Viability Before You Sow

Come spring, it is worth a quick germination test before you commit a whole row. Lay ten beans on damp kitchen paper, fold it over, seal them in a bag and leave it somewhere warm. Check after a week. If seven or more have sprouted, sow as normal. If fewer, simply sow a little thicker to allow for the gaps, and consider saving a fresh batch this coming season.

Sow your saved runners and French beans from late April into May once the soil has warmed, and broad beans either in late autumn or from February. Handle them gently — home-saved seed can be a touch more brittle than shop-bought — and water the drills before sowing rather than after. With any luck, next summer's crop will be every bit as good as the one that produced it.