How to grow runner beans

Runner beans are one of the most-popular summer veg. They're easy to raise from seed and a few plants will produce enough beans for a family.

How to grow runner beans: month by month

Best runner bean varieties

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How we test runner beans

We started off our seeds in a greenhouse in modules containing a Best Buy compost for sowing seeds in early May. They were ready to plant out at the beginning of June, after all danger of frost had passed. We grew each variety up its own wigwam of six canes, planting two plants per cane. As the summer was dry at our test site in the Cotswolds, we watered regularly. We controlled weeds by hand hoeing. Our experts assessed the emergence of the seedlings, the vigour of the plants and the characteristics of each variety, such as height and bushiness, flower colour and the length, colour and shape of the pods. The pods were picked weekly from the beginning of August into early October. Three times during the season we rated the skin quality and stringiness of typical pods. There was little to choose between the taste of the different varieties, although the runner/French bean crosses were typically smoother, sweeter and less 'beany flavoured.

When to sow

Avoiding gluts of beans

Beans produce plentiful crops so to avoid being overwhelmed, the trick is to grow just the right amount of plants for your needs. In the Which? Gardening magazine trial, most varieties produced at least 0.5kg per plant, and our Best Buy runner-bean varieties produced up to 1kg per plant in a season. So a single wigwam of a dozen plants would be plenty for a small household.

Indoors

For the earliest crops, sow runner beans indoors in the second week of May in the south of the UK and the third week of May in the north. Sowing earlier often runs into trouble as the plants can be killed by late frosts when planted outdoors. Sow the seeds into individual small pots or module trays containing a Best Buy compost for sowing seeds. The plants will be ready to plant outdoors when they're about two weeks old - don't plant out if frost is forecast. 

Outdoors

You can sow runner beans in the ground where you want them to grow. Depending on how cold it is where you live, the earliest time to sow outdoors is late May. Don't be in too much of a rush as you can sow outdoors as late as early July.

Caring for your plants

Ground preparation

Runner beans produce better crops in a moisture-retentive soil. However there's no need to dig an old-fashioned bean trench as just digging in or mulching with organic matter, such as garden compost or soil improver, will help.

Creating a support

Use bamboo canes, at least 2.4m tall, pushed well into the ground. You'll see all kinds of imaginative structures on allotments, but when Which? Gardening trialled bean supports, we found that the best three methods were: wigwam, X-frame, and A-frame. 

A wigwam is quick and easy to put up. It also has a neat, compact shape that takes up little space. 

An X-frame is created with pairs of bamboo canes inserted at 45 degrees to the ground, crossing halfway up and tied in the middle. These are strengthened by a horizontal pole tied where the canes cross. The beans are easy to pick as they hang on the outer edge of the support. 

An A-frame is very robust, easy to erect and dismantle, and good at suppressing weeds.

Planting

Space plants at least 15cm apart, in single rows, double rows that are 60cm apart, or around wigwams. Runner beans are damaged by frost so cover them with fleece if frost is forecast.

Watering 

Once they get going, runner beans need little attention, apart from regular watering in dry summers. Give a good soaking every day in hot weather, or twice a week in normal dry conditions. If plants get too dry, they won't flower or set beans well.

How and when to harvest

Harvest in: July to October

The main job is keeping up with picking beans. They need picking every two to three days in warm conditions. You want to pick them before they develop seeds and turn tough to eat. Any that have passed their best should be picked and composted to encourage the plant to keep producing fresh pods.

Common growing problems

Yellowing plants

Planting too early when temperatures are low will cause bean plants to turn yellow and fail to thrive. The best advice is to resow at the right time and start again.

Failing to make beans

Sometimes plants flower but don't produce beans. There are several possible causes, including dry roots and cold or hot nights. Usually cropping picks up as conditions improve. Runner-bean varieties that have been crossed with French beans are less prone to this problem, such as 'Moonlight'.

Read more about plants failing to make beans.

Blackfly

Blackfly is the most common pest and damages the plants by sucking their sap. Either squash these insects or spray them with an organic insecticide.

Read more about blackfly.