It’s probably due to our warmer summers and hotter nights. Unfortunately if the night-time temperature consistently exceeds 16C (62F) runner bean flowers often fail to set - however much you water the plants or spray the flowers. This is particularly true with red-flowered varieties grown from dark, mottled seeds. However varieties do differ. Pale-seeded, white-flowered runner beans show much more tolerance to warmer nights. They crop more heavily in warmer summers.
However if we get a cool summer, red-flowered runner beans perform better than white-flowered ones. So it's a good idea to sow both. Good red-flowered varieties include 'Wisley Magic', the early-cropping 'Red Rum' and 'Lady Di'. 'White Lady' is an excellent white-flowered runner like.
The most heat-tolerant beans of all are French beans and these crop heavily in hot conditions, although they often fail in cooler summers. Climbing varieties take up less space and tend to be less prevalent to slug damage. I recommend ‘Blauhilde’ for its dark-purple beans, lilac flowers and dark foliage and ‘Cobra’ a green French bean. I always sow a mixture of French and Runner beans. And now that we have windier summers I use tripods rather than rows - as bean crops can be devastated by strong summer gales.
Making a bean tripod
- Place a dustbin lid on the ground.
- Use eight tall canes and place the first four opposite each other (as though they were the four main compass points) roughly 12 inches away from outer rim of the lid so that you’re creating a larger circle.
- Slant them into the ground so that they make a tepee shape.
- Remove the dustbin lid and place that last four midway between the compass points and tie securely at the top.
Sowing beans direct
- If you are sowing beans direct into the ground you must wait until mid-May as beans are frost-tender and will only germinate in warm conditions. Place 3 beans round each cane and plant a handful of beans inside the centre of the tripod as spares for gapping up. Water seeds well in dry weather until they germinate.
- Plant some slug decoy plants to protect your beans. These could be lettuces or French marigolds. Slugs adore both and this will hopefully prevent them nibbling the growing points of your beans.
Raising beans in pots
- Begin in mid-April and sow two to each small pot.
- Weed out the poorest of the two when young. Plant two plants to each cane once they have started to produce true leaves. Add some decoy plants as protection. Water until established.
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