Crimson flowered broad beans not setting

[bertiefox]

I'm growing crimson flowered broad beans for the first time and in the polytunnel. As so little seed was supplied from the seed company I wanted to bulk it up by collecting it from the plants in the tunnel.
It's given me a fabulous display of flowers for weeks, and is still going, but very disappointingly almost none have set for pods. There are loads of insects in the tunnel which manage to pollinate most things, and the doors and vents are wide open all day, so I don't think it can just be that.
Why are the beans not setting? Could the temperature be too high? I keep the tunnel pretty humid and moist with overhead sprinklers so I would be surprised if it was dry setting.

[garnetmoth]

I tried to grow fava beans once, but they were in a bad location. Ive always heard of them being some of the earliest beans, so I think of them in cooler weather. My guess is too warm...? Good luck, hope you get some increase from them! (can you keep the tunnel open all night or are there other things that may be damaged?)

[mybighair]

I'm not sure of the reasons but Broad beans don't seem to like polytunnels. At a guess I'd say its the heat, they are a cool season crop and don't set well outside if we have a hot summer, but there may be more to it than that.

I know some beans are triggered to pollinate by rain hitting the flowers, so you could try tapping the plants/flowers and see if that helps.

[grunt]

I concur, it is most likely too warm for them. I first grew favas on the coast in British Columbia, starting to harvest about mid April, when the maximum temperatures were around 12C.

[bertiefox]

Thanks to all of you for the advice. The 'too hot' would seem most likely as we have had an exceptionally warm spring and early summer. The times I've grown ordinary fava beans before the springs have been much cooler. I just hope I get enough seed to keep the strain going, it's pretty enough to grow in the ornamental garden!

[bertiefox]

Update: the solution was to pinch them out. It seemed they would go on getting taller and taller with more and more pretty flowers, until I decided to nip out the tops. Then the beans started setting like mad and I've now got a whole lot of pods with my future seed... as my intention was to bulk up my stock of this pretty fava bean.
So the answer to getting beans to set is to pinch out the tops once they've got to a reasonable size.