Perennial runner beans!!??
In their native Central America the runner bean is a perennial vine with a tuberous root. If you grow runners yourself you may have noticed the large tuberous root on some of the bean plants when removing the plants at the end of the season. Some years ago I forgot to dig up the beans at the end of the season or in the spring, in mid April I noticed some shoots growing from the base of one of the old vines. Over the next week or so several of the other old roots showed the same with some roots putting out up to 5 shoots. All these shoots grew into vigorous vines much earlier in the season than if planted from seed. I now routinely don't remove the beans in autumn but leave them in the ground over winter snapping off the dried vines in January. Most years sometime in April or may between 1 in 4 and 7 out of 8 of the beans send up new shoots, any that don't are replaced with new plants grow from saved seed.
The beans in the photos below are Painted Lady, grown against a south facing wall in a front garden in Sheffield at an elevation of approx 500 ft above sea level. High enough that it's defiantly in the snow on higher ground bit of the weather forecast.
Photo to left taken 16/5/17, shows new shoots growing from old stems and root, this plant is in it's 3rd year of growing back after winter, you can see the multiple stems it had last year. By 10/6 the beans are growing well and starting to climb the strings. Bean plant in 1st photo is the left hand one in the left photo below,the right photo is progress by 22/6.
Runner beans like all beans fix their own nitrogen and anything growing back from a tuber has a store of nutrients in that tuber however for best results a little feed never hurts. Around this time the beans were fed 10 ltrs twice a week for 3 weeks with Growers Ark soil food and Root tonic at 5ml/ltr and Boost it at 2ml/ltr. The plants were regularly watered throughout the season when needed
By 7/7 the beans are well into flowering and we have harvested the first few beans, photos below.
A few more photos taken on the 8/7 showing off the flowers.
These beans kept cropping up to early November, but we had a mild Autumn last year, they will usually keep cropping up until mid October, remember they are planted against a south facing wall.