Runner beans are a veg plot staple – one of the easiest crops to grow, producing an abundance of long green pods from mid-summer to early autumn. Most are climbers, producing large harvests in a small area, with a few dwarf varieties, ideal for containers.
Give runner beans sun, rich soil and plenty of water – they particularly thrive in cool wet summers. Pick the pods regularly when young, tender and stringless, to keep the harvest coming through summer and into autumn.
Month by Month
Most runner beans are climbers – they need tall, sturdy supports and do best in the ground, but can also be grown in large containers. As they grow vertically, climbers produce a large crop in a small area of ground. There are also a few dwarf varieties (up to 45cm/18in tall) – these are quick to grow, but produce a smaller crop. They’re great in containers and raised beds, and in exposed sites. Climbing beans take more time to reach cropping stage, but produce beans over a longer period, from mid-summer to early autumn if picked regularly.
There are many varieties to choose from, with different pod sizes, flower colours (red, white or both), disease resistance and heat tolerance. Look in particular for varieties with an RHS Award of Garden Merit (AGM), which shows they performed well in trials – see our list of AGM fruit and veg.
What & where to buy
You can buy a wide choice of runner bean seeds in garden centres and from online retailers. Many also sell young plants in spring and early summer – ideal if you only want to grow a few or don’t have space indoors to grow them from seed yourself.
Preparing the Ground
A pH of 6.5 (slightly acid) is preferable for a good crop, so add lime if your soil is more acidic.
Putting up supports
Climbing beans need tall supports to twine up, which are best put in place before sowing or planting.
The traditional method is to grow them along a double row of bamboo canes, 2.5m (8ft) tall, with 45–60cm (18in–2ft) between the two rows. Space the canes 15–30cm (6–12in) apart within each row and slope them inwards, then tie each pair near the top to a horizontal cane, to form a sturdy A-frame. If growing more than one double row, allow at least 1.5m (5ft) between them.
If you don’t have room for a double row of canes, you can make a wigwam. Again, use 2.5m (8ft) canes, four or five per wigwam, spacing them 15–30cm (6–12in) apart at the base. Tie the tops of the canes together. Wigwams make an attractive feature in a border or patio container, as well as on the veg plot.
With dwarf beans, you can insert short twiggy sticks between the plants to keep them upright and lift the pods off the soil.
From mid-April to May, start runner beans off indoors on a sunny windowsill, in a propagator or in a greenhouse. This will give you an earlier crop than sowing outdoors.
Use small pots or trays of deep modules and fill with moist multi-purpose compost. Sow one bean into the centre, 5cm (2in) deep, and water well.
Keep in a warm, bright place, at over 12°C (54°F). Seedlings will grow rapidly and need watering regularly.
The young plants can be moved outside once all risk of frost has passed, usually in late May or early June – see Planting out, below.
Sowing outdoors – in the ground
Seeds need warm conditions to germinate, so wait until all risk of frost has passed and your soil has reached 12°C (54°F) – usually by mid-May in the south of the UK, and two weeks later in the north.
Before sowing, prepare your site well and put supports in place – see details above. If your soil is heavy and wet, warm the ground in early spring by covering with clear plastic or cloches for about four weeks ahead of sowing.
Then sow the large seeds individually 5cm (2in) deep – two at the base of each bamboo cane. Once they germinate, thin to one seedling per cane, and protect from slugs and snails.
When sowing dwarf runner beans, allow 30cm (1ft) between plants and 50cm (20in) between rows.
Sowing outdoors – in containers
You can sow seeds outdoors into pots of multi-purpose compost in spring – either into small pots for transplanting into the ground later, or into large containers as their final growing site.
Sow one bean per small pot, 5cm (2in) deep, and place in a cold frame or sheltered spot. Once the plants reach 8cm (3in) tall, in June or July, plant them into their final positions – see Planting out, below.
Alternatively, sow into a large container as their final growing site. For dwarf beans the container should be 30–45cm (12–18in) wide, and for climbing beans 75cm (30in) wide, 45cm (18in) deep and heavy enough to keep it from toppling over once the climbing beans are at the top of their supports.
For climbing beans, insert a wigwam of 2.5m (8ft) canes (see Putting up supports, above) before sowing.
Then simply sow the seeds into the container of potting compost, 5cm (2in) deep and 15cm (6in) apart. With climbing beans, you can sow two seeds at the base of each cane, then thin out to leave the strongest seedling.
Wait until after the last frost before planting indoor-raised or bought young plants outside. Harden off to acclimatise them to outdoor conditions for a couple of weeks, either by putting them in a cold frame or placing them in a warm, sheltered spot, covered with fleece.
Make sure your planting site is ready – see Preparing the ground and Putting up supports above.
If planting in a container, choose multi-purpose or loam-based compost. Containers should be at least 75cm (30in) wide and 45cm (18in) deep for climbing beans, and 30–45cm (12–18in) wide for dwarf beans.
Plant one climbing bean at the base of each bamboo cane and water well. Loosely tie the stems to the canes to get them started.
When planting dwarf beans, space plants 30cm (1ft) apart.
Spread a mulch of well-rotted manure or mushroom compost around plants in July to help hold moisture in the soil.
Why add mulch? An organic mulch, such as garden compost or well-rooted manure, is a great way to add nutrients and valuable micro-organisms to your soil. It also holds in moisture and deters weeds.
Keep the growing site weed-free. Consider planting through weed-suppressing membrane – this reduces the need for weeding and prevents the pods of dwarf beans being damaged by contact with the soil.
Encouraging pods to form
Runner bean flowers sometimes fail to ‘set’ (produce pods) – there are several possible causes and solutions:
Ensure the soil is constantly moist and doesn’t dry out. Add mulch after planting and water regularly and generously, ideally in the evenings
Flower set is better in alkaline, chalky soil. If your soil is neutral or acidic, try applying lime
If this is a recurring problem and you live in a mild area, try growing varieties with some French bean parentage, which set pods more easily in warmer summers. Examples include ‘Firestorm’ and ‘Moonlight’
Pick pods when young, tender and stringless, about 15–20cm (6–8in) long. The pods should snap easily and the beans inside should still be small and pale in colour.
Regular harvesting – ideally every two to three days – is essential to prevent any pods reaching maturity. Once this happens, plants will stop flowering and no more pods will form.
Runner beans are one of the easiest vegetables to grow, but they are tender, so must be kept indoors until after the last frost. If a late cold snap is forecast, cover your plants overnight with cloches or fleece.
Seedlings and young plants are vulnerable to slugs and snails. Keep watch, too, for black aphids on the shoot tips and under leaves – squash them or wash them off with a jet from the hose before they get established.
These large, vigorous plants also need plenty of moisture to crop well, so water them regularly, especially during dry spells. Hot weather can also hinder cropping.
Occasionally, fungal or bacterial diseases such as rust or halo blight can develop, while in warm, dry conditions red spider mites can cause problems.
The southern green shield bug is a relatively new pest found on runner beans and – although only in certain locations at present – is more serious than our native shield bugs, which do negligible harm to runner beans.
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