How to Grow Beans: Build the Frame Before You Sow

Beans are the most productive thing I grow per square metre, and the two mistakes that spoil them are both about sequence rather than skill: building the support after sowing, and not picking often enough. Get those right and one short row will feed you for two months.

The short answer

Build the frame first, then sow at the base of each cane, because a climbing bean reaches within days. Sow only after the last frost, and direct into soil that has reached about 12C. Water deeply and consistently once flowering starts, which is when runner beans drop flowers if they are dry. Then pick every two or three days and pick young, because one pod left to mature slows the whole plant.

Which bean, and my recommendation#

Climbing French beans

Round, fine pods, mild flavour, sets reliably in heat, crops for six to eight weeks. What I would grow if choosing one.

Runner beans

Heavier cropping, long flat pods that get coarse and stringy if left. Needs consistent moisture or the flowers drop. Traditional and demanding.

Dwarf French beans

No support needed, crops in a shorter concentrated burst. Ideal for containers and for succession sowing every three weeks.

Borlotti and drying beans

Grown to maturity and shelled or dried rather than eaten in the pod. Needs a long warm season.

Broad beans

A different crop entirely: sown in autumn or very early spring, hardy, and finished before the others start.

The traditional choice in Britain is runner beans and I think climbing French beans are the better plant for most gardens. The pods are finer, the flavour is better, and they do not sulk and drop flowers the moment the weather turns hot and dry.

Build the support first#

This is not fussiness. A climbing bean seedling puts out a searching shoot within days of emerging, and if there is nothing to grip it flops and tangles into its neighbours.

Pushing canes in later means driving them through the root zone of an established plant, which checks it badly.

Cane wigwam

Six to eight canes tied at the top. Stable in wind because it is a tripod, and it fits a container. My default.

Double row with crossed canes

Two rows of canes crossed and tied to a horizontal cane along the top. Most productive per length of bed and easiest to pick.

Net between two posts

Cheapest for a long run, and nothing to tie in. Posts need sinking 60 cm, because a netted row of beans in August is a sail.

Height

Two metres minimum. Beans will reach the top and keep going, and you will be picking on tiptoe if you go shorter.

Sink the posts or canes deeper than feels necessary. A frame loaded with beans in a summer gale is the most common structural failure in a vegetable garden.

Sowing, and not being early#

Beans are completely frost tender and they rot in cold wet soil rather than germinating.

Two options. Sow indoors in pots two to three weeks before your last frost date, harden off, and plant out after it. Or sow direct once the soil has warmed to about 12C, which in many places is a fortnight after the frost date.

Direct sown beans catch up with indoor sown ones remarkably quickly, so the head start is smaller than it feels.

Sow two seeds per cane, 5 cm deep, and thin to the strongest if both come up. Keep a few spares in pots to fill gaps, because slugs take young beans reliably.

Watering, and the flowers that will not set#

This is the section that matters, because it explains the commonest bean complaint.

Beans flower and then fail to set pods when they are hot and dry at flowering. Runner beans are notably worse for this than French beans.

So from the appearance of the first flowers, water deeply and consistently, and mulch the base of the plants to hold it. That is the fix.

Key points

• Water at the base, deeply, two or three times a week in dry weather rather than a light daily sprinkle.
• Mulch once the plants are established. It does more for consistency than any watering routine.
• Above about 30C, runner bean flowers will drop regardless. Climbing French beans cope far better.
• Spraying the flowers with water is widely advised and does not help. The water needs to be at the roots.
• Poor pollination is rarely the cause. Beans are largely self fertile, and it is almost always moisture.

Picking, constantly#

A bean plant exists to make seed. Once a pod matures, the plant has succeeded and slows down.

So pick every two or three days in high summer, and pick young. French beans at pencil thickness, runner beans while they still snap cleanly and before the pods go lumpy and stringy.

Look underneath and inside the frame, where the ones you miss are hiding and quietly stopping the plant.

Done properly, one row of climbing beans crops for six to eight weeks. Left for a fortnight it more or less stops, and getting it going again is slow.

Feeding, and the nitrogen question#

Beans need very little feeding. In soil with compost in it they want nothing, and a nitrogen rich feed gives you a magnificent leafy plant with modest cropping.

On the nitrogen fixing: beans do fix atmospheric nitrogen via bacteria in root nodules, and most of it ends up in the plant rather than free in the soil. The practical way to capture it is to cut the tops off for the compost heap at the end of the season and leave the roots in the ground, rather than pulling the whole plant out.

That is a real contribution and a modest one. It is the reason brassicas traditionally follow legumes in a rotation, and it is not a substitute for adding organic matter.

What can go wrong#

Slugs on young plants. The main early threat. Keep spares in pots, and go out at dusk for the first fortnight.

Blackfly on the growing tips. Pinch out the affected tips, which removes most of the colony, and let the ladybirds and hoverflies deal with the rest. Rarely worth spraying.

Halo blight, brown spots with pale rings, spread by wet foliage and seed. Water at the base, do not save seed from affected plants, and rotate.

Tough stringy pods. Left too long, every time.

What it costs#

A packet of seed

$2 to $5, and enough for two or three seasons. Beans are among the cheapest crops to start.

Eight bamboo canes

$8 to $18, and they last several years if stored dry over winter.

Pea and bean netting with two posts

$25 to $50 for a long run, and the least fiddly option to pick from.

Mulch

$0 to $30. Free if you make compost, and it is what keeps the flowers setting.

Nothing else

No feed needed in decent soil, no netting against birds, no special equipment.

Where this needs adjusting#

In a hot climate, grow climbing French beans rather than runners, mulch heavily, and consider afternoon shade for the flowering period.

In a short season, start indoors, choose an early variety and grow dwarf French beans, which crop faster than climbers.

In a windy garden, use a wigwam rather than a flat netted row, sink the canes deeper, and consider dwarf varieties, which present nothing to the wind.

Where the guidance here comes from#

The frame-first rule and the pick-young rule are the two things I would want anyone to take from this, and both come from doing the opposite. The nitrogen fixing explanation is deliberately measured, because the benefit is routinely overstated. For sowing temperatures, spacing and disease the RHS advice on growing your own is the reference I check, and Garden Organic is the better source on rotation and on why the roots should be left in the ground.

The short version#

Build the frame before you sow, two metres tall, sunk deep. Sow after the frost into soil at about 12C. Water deeply and mulch from the first flower, because that is when dry plants drop their flowers. Pick every two or three days at pencil thickness. Cut the tops for compost at the end and leave the roots in.

Related reading#

• Vertical gardening: why a netted row of beans yields four times what the same ground would sprawling.
• How to start a vegetable garden: where beans fit in a first year.
• Garden planner: rotation, and why brassicas follow legumes.
• Container gardening: pot volume for dwarf and climbing beans.