Dealing with a Glut of Runner & French Beans

On many Scottish plots late July is still the manageable phase: a handful of pods every couple of days. Then the weather turns warm and settled, the plants that sulked through a cool June catch up, and you go from a bowlful every other day to filling a trug every morning. Miss two picking sessions in that window and the plant has already moved from productive to problem. The cause is one mechanical fact: a pod you don't pick doesn't just sit there, it shuts the plant down.

Why leaving pods on the plant stops future cropping

Runner and French beans are grown for their immature pods, but the plant's own goal is mature seed. Once the beans inside a pod start to swell and the pod toughens, the plant registers that a batch of seed is on its way to being finished. For runner beans, once this happens plants stop flowering and no more pods form: pods left on the plant start to swell and set seed, which inhibits further pod production.

Picking young pods removes that signal, so the plant keeps flowering and setting new pods in an attempt to get there. That's why the advice for both crops is the same: pick every two to three days once cropping starts, for as long as you want it to keep producing. Skip that rhythm for a week and pods that were pickable on Monday are tough and stringy the following Monday, and the plant has started putting its energy into finishing those seeds rather than new flowers.

So the fix for too many beans is never to pick less. Pick everything on schedule, even pods already a bit past their best, because leaving them on to deal with later is exactly what stops the plant producing the beans you want. The runner bean growing guide and French bean growing guide give the rule in brief.

If flowering has stopped and there's no backlog of overgrown pods to explain it, check the shoot tips for black bean aphid (blackfly). A heavy colony can suppress new flowers on its own, and the other common cause is lack of moisture at the roots: water in dry weather (5-11 litres per square metre, twice a week) and mulchA layer of material spread over the soil around plants to suppress weeds, retain moisture, and improve soil structure as it breaks down. Full definition → to hold moisture.

How long is too long

There's a narrow window between perfect and too far gone.

Runner beans are best at about 20-25cm long, while young and tender, when the pod snaps cleanly and the beans inside are still small. Beyond that the outer skin develops fibrous strings along the seams, then the pod turns leathery and the beans swell and show through the skin. A pod can cross that line within days of warm growing weather, which is exactly the settled spell that tends to trigger a glut. A stringless variety such as 'Moonlight' (a runner and French bean cross that is stringless and crops well) keeps a slightly overgrown pod usable rather than a write-off.

French beans are picked at 15-20cm, when they snap easily and before individual beans show as bumps. Their pods are thinner and toughen noticeably quicker once they start filling seed, so the window is measured in days.

Neither species gives much grace. Pick-every-2-3-days works because it matches the speed at which a pod moves from ideal to overgrown.

Runner beans vs French beans at a glance

Spreading the glut with succession sowing

Regular picking controls how fast one planting deteriorates, but it doesn't stop every plant in a bed hitting peak production in the same fortnight. For that, sowing timing matters more.

Dwarf French beans are the crop most worth staggering. A dwarf plant crops for a few weeks and then tails off, so one sowing date means one concentrated glut. Sowing every three weeks, from late spring (once the soil has warmed) to mid-summer, gives a continuous supply instead. Beans are frost-tender, so check the regional frost dates before sowing or planting out. Scottish outdoor sowing only opens once the soil is reliably warm, so the season may have room for fewer rounds than a longer southern one, but each wave still hits its cropping window out of step with the one before.

Climbing French beans and runner beans don't respond the same way, because one plant crops across a long window rather than in a burst. Staggering sowings of climbers mainly staggers when the plants start, and in a compressed Scottish season there may not be enough calendar left to make a second sowing worthwhile. The better lever for climbers is fewer plants if a glut has been a problem before, since one wigwam picked every two to three days will out-produce most households' eating rate.

The Scotland factor: why the glut can be uneven

Runner beans need insects, mainly bumblebees, to complete pollination, and without a visit the flower drops instead of setting a pod. A lack of pollinating insects, perhaps because of cold, wet or windy weather, is a direct cause of poor pod set. French bean flowers, by contrast, are self-pollinating.

A changeable Scottish summer produces exactly the conditions that disrupt this. A cool, breezy, showery stretch in late July can mean very few runner bean flowers get pollinated, so plants keep flowering with few pods forming. Then a settled warm spell arrives, bumblebees become active again, and flowers open in that window all set pods at once. The result is a sudden, dense flush all reaching pickable size within days of each other, not a steady build to a peak, and it isn't a sign you've done anything wrong. A sheltered site, such as a fence line or hedge rather than an open bed, encourages bees to visit. Spraying flowers with water to help pods set hasn't been shown to work and may deter bees.

What to do with the surplus

Pods keep best unwashed and loose in the coldest part of the fridge, for roughly 3-5 days before they soften and lose their snap. Washing them first or sealing them in an airtight bag tends to shorten that, so a bumper picking day needs dealing with quickly. Options for a surplus:

• Freeze them. Top, tail and slice, blanch briefly (2 to 3 minutes is typical for runner beans), cool, dry and freeze loose on a tray before bagging. Frozen without blanchingExcluding light from part of a growing plant, usually by earthing up, wrapping or covering, so it grows pale, tender and less bitter. Full definition →, they tend to deteriorate within weeks.
• Pickle French beans. The pickled French beans recipe uses young, slim pods and a tested brine.
• Leave some to mature for seed. Let a few pods ripen on the plant until brown, dry them, and store the beans in a labelled paper bag in a cool, dry place over winter. Seed from French beans comes true because the flowers self-pollinate. Do this on one plant, since leaving pods on the others stops them cropping.
• Give them away. A neighbour or a plot-sharing allotment friend will rarely say no to a bag of fresh beans.

Common questions

Sources