How to grow runner beans

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.

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.
 

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.

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.

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.

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.

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’