I know we all say it every year but this year will be stringless. No more tough pods or chewy beans.
I know several readers have problems with runner beans (Phaseolus coccineus), being stringy,being small or just not being there when they should.
Let’s go through the basics then:

The seed.
These should be sound but not necessarily fresh. Beans, like all pulses, can be dried an preserve for years without deteriorating. The essential food to get them started is stored inside the shell.Don’t worry if they look shiny and wrinkle. They are fine as long as they are not damaged or have holes in them from weevils.
Moisture is the trigger that brings them back to vibrant life.

Varieties make a difference. I’ve grown both white and re flowered types with no discernible difference in results. Some however swear by one or the other. There are varieties which have been selected over several decades to produce longer, thinner, more tender or less stringy bean pods. Some can produce earlier crops and many produce dwarf plants, making container growing easier.
I do not recommend soaking seeds before sowing or dusting with any sort of compound. The germination rate is pretty high without any help and soaking has been known to contribute to Halo Disease.

The soil.
Here’s the important bit.

Start a trench.Fill your trench.Your trench is your friend.

Runner beans grow fast and thirsty. Preparation is everything. Choose a sunny or at least shade free location and make it weed free. Runner prefer a soil acidity of about ph 6.5-7.0 so lime if your soil is too acid.Runners need lots of water and lots of root space so prepare a trench as long as your run of canes will be and about a spit (spade blade) deep. This needs doing February to early March so it can be filled over the following weeks with compostable waste. This doesn’t need to be rotted down as it will be covered and will mainly be used as a sponge to store water for the roots. The food aspect is of little value in this way but will provide plenty of goodness to the soil in the future.
Anything biodegradable that will hold water/moisture can go in the trench. Newspaper, wool, old used compost from pots and tubs or baskets,straw, grass clippings and garden and kitchen raw veg waste.
Cover with soil when you are ready to plant out your Runners, after soaking the trench first. This ‘sump’ or reservoir will help maintain the moisture levels for the plant which, remember, grows rapidly during what should be our hottest season.
The Support.
Second only in importance to the soil. Beans are grown up supports. They are a twining vine and will happily wrap themselves around any support you offer but also around anything else, including nearby stems from other plants or runner beans. The stems themselves can thicken rapidly and become very tough and rigid before harvesting so a strong support system is recommended, and one which can withstand having the old dry stems removed after the beans have finished. Nets can be utilised if available but are near impossible to reclaim intact and straight strong bamboo canes are more than suitable in most circumstances. Structure designs vary from basic leant against the wall to elaborate permanent structures that involve scaffold poles or wooden frameworks. The important features are strength against the weight of the vines and pods and stability against any late summer wind.

So,we have the seed, soil and support. The rest is down to nature. Water and sunlight. As we can’t rely on rain despite the reputation of our English Summers, we need to supplement by hand. That means watering at least daily, twice daily if possible. Early and late . Avoid the hot period. Water droplets act like magnifiers in direct sunlight. By watering I mean copious amounts. If you can mulch, even better. Consider one 9 litre can of water between two plants per day a reasonable amount. More if the sun is strong. The reservoir you’ve built will help to store all this water or the plants to use during the day and night.
Water can help with pollination too.

Bean flowers and seed pods

If the flowers are not setting, i.e. fertilising and bearing seed pods, a light spray with water in the late evening can help. I’m not sure why, whether it encourages nocturnal insects to visit or if the water helps the pollination itself, whatever it is, it seems to help. I haven’t experienced any great issues with lowers setting so I can’t vouch personally.

 
Bean plants can either be grown from direct sowing or, as most growers do, from planting out those started indoors earlier. Although technically a perennial plant, Runners are treated as half hardy in the UK. so be sure to harden of any greenhouse plants before risking planting out. Sow seed in pots from April. Don’t be tempted to rush things. Pot bound plants will take longer to recover and start growing again. Double up if you are unsure and sow 2 seeds per station, removing the weaker when they germinate. Once again, germination has never really been an issue.

Plant out 2 plants per cane/support . Water well and stand back. No, seriously they don’t grow that suddenly but when they do grow they can gain several inches over night. Bear this in mind when the vines reach the top of the supports, nip out the growing tip about six inches before the top as the vine will continue to grow a little before the plant directs its energy to setting seed. Don’t panic at those words. Seed pods are the parts we eat.
The Runner Bean seed pod is eaten before the seeds themselves develop. Harvest the pods before you see any lumps develop. Those lumps are the seed. Harvest regularly. See development and a lack of moisture can cause the pods to grow tough and stringy.  Water regularly, harvest regularly. Do both in one trip. Be ready to fill several carrier bags at the height of the growing season per harvest. Towards the end of the summer the plant will slow down production of pods an those will start to become tough. Those can be saved for seed collection if you like but will not be much use in the kitchen. 
One last tip:
Legume roots (runner beans are part of the legume family) capture nitrogen from the air as they grow and store it in nodules around their roots. When you clear your plants after they have served their purpose, cut the stems just above the soil and allow the roots to rot down in the soil, releasing the nitrogen into the soil for future plants to use. The actual amount of nitrogen is thought to be pretty minimal but there is nothing to be gained by pulling them so why not?
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