In the UK runners are eaten exclusively as green beans. To eat them as green beans pick them before you can even feel the bean distinctly inside the pod. It is not possible to give a length because that will depend on variety and growing conditions. Some will grow a foot long and remain tender, others not so. By regular picking when they are young and tender they will keep producing. Depending on the variety you may need to string them (or use a bean slicer).

If you intend to use them for shellies they can be a bit bigger but personally I am not a fan and they have not been bred for this purpose. As for dried beans, I've never even attempted to use runners for that.

I grow them every year just for aesthetics. I've never eaten them, probably because I never have enough at one time. I just let them go to seed & then harvest the seeds for the following year.

FWIW, I did read (somewhere) that you shouldn't eat them raw because they contain phytohaemagglutinin, which can be toxic in large quantities, but eating them cooked is fine.

We probably won't get very many a time either, but we can pick them and mix them in with the beans from the bush bean plants to cook for dinners. Just wasn't sure how big to let them get.

Thanks,
Edie

"... in large quantities ....." is the key regarding toxicity. I have nibbled on plenty of raw ones over the years.

Runners grow far more successfully here than common beans and are to be seen in every vegetable patch.

I grow scarlet runners almost every year for the flowers and mature beans, which to me resemble butterbeans. I grow other beans for snap beans. In terms of productivity, the runners can't keep up with a good pole bean like Ky wonder.

In Austria (Styria), these are known as Käferbohnen or Beetle beans. The purple-mottled dried beans are cooked and eaten as a salad condiment, preferably with some pumpkin seed oil vinaigrette. Yum!
We are trying to grow some this year to get some of the dried beans.

We had our first picking of these for dinner tonight. They are wonderful! Imagine that - I'm almost 60 and this is the first time I've ever tasted these. Oh, what I've been missing all these years - silly me!!! So we only planted a few plants this year since we had no clue what they were like. Next year - all around the fence!
Edie

Anyone wanting to grow scarlet runner, I've had near perfect germination from dried beans in the bulk section at Whole Foods Market for a fraction of the price of buying seeds. The three plants I have right now were scavenged off the floor in the bulk section. Swear someone could start an entire farm from the floor sweepings of that bulk section.

Over here there are many. many named cultivars selected for various traits including stringlessness. If you can only obtain something generically called 'Scarlet Runners' you may not be getting the best flavour. A bit like growing a crop of 'cabbage' or 'tomatoes' without a varietal name.

coffeehaus - thanks for the mention of Kaeferbohnen. I'd never come across that use of runners before. I have a stack of dried beans - I always keep far too many for seed. Maybe I'll try that recipe.

Millions of runner beans end up on composts heaps here, especially at the end of the season, because they are considered unusuable once past the green bean stage.

Here is a link that might be useful: Runner bean thread

I too have planted some under the trees just as flowering beans.
They do not produce enough(like pole/bush beans) I will harvest the few there is as shelly. I started mine in April(I think), they are still going with 3 to 4 hours of sun.
Another bean that I plant for just flowering purpose, is Hyacinth Pole Beans (aka lab lab) They are hot weather lovers and no are flowering. They are pretty, (flowers , beans, foliage) smell real nice and bloom till frost.