Drying
Leaving the pods to hang: drying runner beans in a wet autumn
The hardest part of saving runner beans in London is not the bees but the weather at the end of the season. October here is usually mild and wet, and pods that are nearly dry can go mouldy in a week of drizzle.
Packed 12 October 2025Re-checked 25 January 20266 min
Knowing when a pod is ready
Pods for seed stay on the plant long after the eating pods have been picked. They swell, the beans inside grow fat and colour up, and then the pod slowly loses its green, going yellow, then pale brown, then papery. A pod that is ready feels light and leathery, and the beans move inside it when you shake it. That rattle is the sign I wait for. Beans taken from a soft green pod usually shrivel as they dry, and many of them will not germinate.
Timing depends on when the pods set. Pods formed in July have all of August and September to ripen, and those are the ones I mark for seed. Pods that set in late August are a gamble in a normal year; they may reach full size but not dry before the frosts. On our site the first light frost usually arrives in late October or November, but a wet spell before that is the real danger, because nearly dry pods soak up rain, turn black and grow mould inside.
Pulling the vines into the shed
In a dry autumn I pick each pod as it rattles and lay it in a shallow crate. In a wet one, which is most of them, I cut the whole plants at the base once most of the seed pods have turned yellow, pull the canes out, and hang the vines upside down from the shed roof. The pods carry on drying from what is left in the stems and leaves. The shed looks like a witch's kitchen for a fortnight, and this method has saved my seed in at least three of the last five years.
The shed is not warm, so moving air matters more than heat. I keep the door propped open on dry days and shut when it rains, and I check the hanging pods every weekend for black patches. Any mouldy pod comes down and is opened at once. Often the beans inside are still sound if the mould is only on the pod, and they go straight onto a tray indoors. A bean with mould on the seed coat itself goes on the compost, because it is not worth risking the rest of the tin.
Shelling, and the hammer test
Shelling is a job for November evenings at the kitchen table, with the radio on and a newspaper spread out. Dry pods split with a twist between the fingers. The beans go into shallow trays in a single layer, sorted as I go: shrivelled, split, discoloured and very small seeds come out, and so does anything with a small round hole, the sign of a bean weevil. The good seed then stays in the trays for another two or three weeks in a heated room, stirred now and then with a hand.
The test for dryness is a harsh one. A properly dry runner bean should not dent when pressed with a thumbnail, and if you put one on a board and hit it with a hammer, it should shatter into pieces rather than squash flat. It feels like a waste of a good bean, but I do it to two or three from every lot before anything goes into a jar. Beans that are not fully dry go mouldy in storage, and a sealed jar simply traps the damp in with them.
- Wait for the rattle in the pod before picking.
- Pull whole vines under cover if the forecast is wet for a week.
- Sort out shrivelled, split, discoloured and holed seed while shelling.
- Dry in single layers indoors for two or three more weeks.
- Thumbnail test first, then the hammer on a spare bean.
Cool, dark and dry
Seed lives longest when it is cool, dark and dry, and of the three, dry matters most. My beans go into paper envelopes, one lot per envelope, and the envelopes stand in a big glass jar with a screw lid. At the bottom of the jar sits a sachet of silica gel, the kind that comes in shoe boxes, dried out in a low oven first, or a small cloth bag of uncooked rice dried the same way. The jar lives at the back of the understairs cupboard, the coolest dark place in our terraced house.
Every lot of beans also spends a few days in the freezer before it goes into the jar. Bean weevils are uncommon on beans grown outdoors in Britain, but they arrive in beans brought from elsewhere, swap envelopes included, and their eggs can hatch in storage and ruin a jar. A few days of freezing kills them. The seed must be properly dry first, or ice crystals damage it, and it must come back to room temperature before the envelope is opened, so that no condensation settles on the cold seed.
Lifting the roots, for the curious
Runner beans are perennials in the mountains of Central America where they come from, and the plant makes a thick, tuberous root. In a mild London winter some roots survive in the ground on their own, and on our site a clump of runner beans sometimes appears in May where nobody sowed them. A few people lift the roots in autumn, like dahlia tubers, keep them in dry compost in a frost-free shed, and plant them out again after the last frost. The plants start earlier and flower sooner.
I tried it with six roots two winters ago. Four survived in a crate of old compost under the shed bench, two rotted, and the four that grew gave pods a couple of weeks before my sown plants. It is a pleasant experiment, but it is not seed saving. Plants from lifted roots are last year's plants, with last year's crosses in them, so I treat their pods like any other lot and label them as coming from overwintered roots. Seed is still how the variety carries on.
Written from the notebook in the shed, on half a plot in Walthamstow.