Runner beans (Phaseolus coccineus) are a bit of a British institution, though they are grown in Ireland too. Because I have had to look further afield for seeds this year I have noticed that European catalogues still sell this plant as an ornamental rather than as a crop. I suppose it is not so bizarre because the flowers are showy. The flowers are typically scarlet but there are some with red and white flowers, others are salmon pink and others are white. Runner beans are possibly my favourite summer vegetable but the beans need to be picked young or older varieties can be stringy – many modern kinds are less so. It is traditional to try to grow the longest bean you can but these are inedible. Unlike French beans where you can eat the dried seeds if you can’t keep up with the crop, you can’t do this with runners. Runner beans are, strictly, perennial and you can save the tuberous roots if you keep them free of frost, to plant the next year, but no one bothers.
Runner beans are widely planted but they cause a lot of heartache, mainly because they bloom but do not set pods. More of that soon. I will start with the basics. You need to provide these twining plants with support and this can be a wigwam or double row of canes. Traditionally hazel rods were used and the stems do grip these better than canes. I often make a wooden framework and set up twine vertically and they climb up this perfectly – and if you use natural twine the whole lot can be cut down and composted at the end of the year – I hate using plastic net. Wigwams are a nice idea but I don’t like them because the beans hang below the foliage and they are very hard to see hanging in the interior of the wigwam.
You can also get dwarf runner beans, such as ‘Hestia’ and these are OK in pots but I hate them in the open garden because the long beans flop on the soil and get filthy, eaten by slugs and bend into awkward shapes. It is bad enough prepping runner beans when they are straight – don’t expect me to show any gratitude if presented with a handful of grubby, bent beans.
Runner beans need a rich soil that does not dry out in summer. They also prefer some lime in the soil. As a child we always dug out the bean trench in autumn and it was left open all winter so we would fill with all the kitchen waste. Then lime was sprinkled over this in March and the trench filled in to leave a mound of soil. Runner beans are not frost hardy and the large seeds do not need to be sown until about a month before the date of the last frost of spring – which means I sow in mid April. I sow in cell trays and the individual plants can be put out in mid or late May without disturbing the roots and before the seedlings start to make their long, thin shoots (below). If you sow too early and you have rambling plants to put out they rarely recover from the stunting of being potbound.
A sunny spot is needed, ideally sheltered from strong winds. And you must protect the seedlings from slugs and snails. Keep the plants moist and they will soon be racing up the supports.
I would plant them about 20-25cm apart. I often pop in a spare seed at the same time as planting the seedlings.
And then the flowers come. But a good crop of flowers does not always translate into a good crop of beans! Often the flowers drop off and no beans form. There are many reasons for this happening:
Birds – Sparrows in particular, often attack runner bean flowers. Birds see red flowers, unlike insects such as bees, and associate them with a sugary drink of nectar. So rather than just being naughty they are having a sugar fix when they peck off the blooms – it is annoying though. If you grow pink or white-flowered beans they leave them alone.
Bees – Bees are not attracted to red flowers but bumblebees in particular will discover that the flowers contain nectar. The trouble is that they are too clever and they find out that the best way to get to the nectar is to chew a hole in the back and suck the nectar out, without pollinating the flowers. Once again, try the pink and white flowers. Some people suggest spraying the plants with sugar solution but I have never tried because it sounds a perfect way to attract flies and wasps.
Cold water – It is often said that beans will not set if the plants are watered with cold, mains water – the shock of the drop in soil temperature makes the flowers drop off. I am not wholly convinced but it is better to keep the soil constantly moist rather than let them dry out and then soak. Drought will cause a lack of pods.
Lime – It is sometimes thought that a lack of lime will cause poor setting. I am not sure about this but lime is beneficial anyway.
Steamy nights – The most likely cause of poor setting is high night temperatures. Although runner beans are Mexican they grow at high elevations and if the night temperatures is too high the flowers will not produce pods. This often happens in July and August when the plants are just coming into flower. Don’t panic if the first flowers do not form pods – there is nothing you can do. When the nights cool the pods will form. By September you will be picking baskets of them
Look out for Runner-French hybrids, listed in the catalogues as such. Because French beans do not suffer from pollination problems, these hybrids set pods easily – every flower is a pod.
Because beans like lime and they add nitrogen to the soil it makes sense to follow them with brassicas in a rotation.