Kitchen Garden Forum

Am I right in thinking that the flowers on runner beans have to be sprayed (water) for them to 'set'?
The last time I grew them I did do this but would like to know the reasoning behind it....and also if it is completely necessary.
Of course, wouldn't be doing it with the hose this time but a spray bottle just as good I would think.
I'd appreciate your comments.

Glory B

I've never done it gloryb, and have always had good crops. It's traditional - would be interested in the rationale. I do mulch my runners (and everything else) very heavily though, don't know if that makes a difference?

I don't do it either and have huge crops of beans. There's all sorts of stories about spraying with water; spraying with lemonade (to attract bees I think), etc etc. I have sprayed with water in the past when I grew beans in the garden and could use a hosepipe for watering but it wasn't a deliberate thing, I just got distracted. Made no difference anyway.

Hi Chantal and Sprout....I'm sure it was my Dad that gave me this tip....maybe it's an old-wive's tale.
That's an interesting tip about the spraying with lemonade Chantal, but if there's no real need to spray....especially with water being as scarce as it is....I shan't bother. I'll concentrate more on the mulching etc..

Many thanks,
Glory B

I believe its to do with pollination, like stirring up some flowers with a paint brush. I think it is supposed to spread the pollen onto the anthers.

I'm sure someone else know the science though.

David

I have in the past sprayed the flowers, in the coll of the evening, but it did not make a huge differance as far as I could tell, always got plenty of beans.

The real pain is with the bees, they can drill into the flowers from the back to get at the nectar resulting in no bean.......

Dont think it is the normal honey bee that does this though.

Jerry

Hi Jerry and David...got this info from RHS site...it mentions the fact that it's not necessary to spray flowers...also info on the 'boring' bee plus a couple of other snippets.
You are both old hands I'm sure but should prove interesting to other beginners like myself.


RHS Help & Advice
Failure of runner beans to set pods
It is normal for runner beans to set more flowers than they can carry as beans, but attention to the following points should ensure a worthwhile crop.

Good cultivation
Runner beans are deep-rooted, requiring a well-drained but moisture-retentive soil to which organic matter has been added the previous autumn. A pH of 6.5 is preferable (acid soils may need liming). Rotate the crop annually to reduce soil pest and disease problems. Don’t sow or plant outside until late May to avoid cold damage (runner beans need a minimum soil temperature of 10ºC/50ºF to germinate).

Watering
Watering the soil at the base of the plant has a beneficial effect on flowering and pod setting. Apply a mulch to conserve soil moisture. In dry weather water from when flower buds appear, giving 5-11 litres per sq m twice a week throughout the cropping period. Syringing flowers with water doesn’t help pod set, but if done in late evening may cool the flowers.

Temperature
Warm temperatures, especially at night, may inhibit bean formation by preventing pollen grains from germinating. Cropping should resume when cool nights return in September.

Pollination
Flowers need bees (mainly honey and bumble) to pollinate the flowers. Cold, windy weather deters bees, so position plants in a sheltered site. Runner bean nectar isn’t very rich in sugars, and bee numbers visiting runner beans often increases after July, when more attractive nectar sources have finished flowering.

Short-tongued bees can’t reach nectar from the front of the flower, and so bite a hole in the flower base to gain access. This isn’t adequate for pollination. Although there’s no way to prevent this, other bees usually pollinate sufficient flowers for a good crop. Growing sweet peas nearby will also encourage more bees to visit the area.



Well I see I have done one thing right, although not intentionally I have to admit. To grow sweet peas nearby, that's so long as they get a move on!

Glory B

Hello Glory B, hope your well.
I noticed the R.H.S site say that syringing the flowers late at night may cool the flowers.
Then they say cropping should resume with cooler nights.
Well the way i look at that, is if you syringe the beans a couple of times in an evening it's got to help.
Or do you think i'm stuck in my ways.

Kind regards Old Herbaceous.

Theres no fool like an old fool.

Thanks Herbal I'm feeling fine except for a bit of wilt damage due to this humid weather.
It's not so bad being stuck in your ways as you ask. If these particular 'ways' work then why change them?
Yes, I see what you're saying....so there was a method to my Dad's madness after all?
Well I have flowers forming on my container grown beans....so, when it cools down I shall be out there with a fine water spray.....just for him!

Best regards Herbal,
Glory B

Glad to see the RHS has caught up with me - I've banged on about moisture at the roots (7 barrow loads of compost in 25' x 2' trench) and my parallel rows of Broad Beans, Sweet Peas and Runner Beans (the BBs are full of flowers and insects now, the SPs are just starting and will keep them going until RB time, they are just starting to climb) ever since I've been on the forum.

Humble bees are one reason to appreciate derelict plots and mossy nettle patches. Somewhere for them to nest.
I remember my dad showing me as a very small boy a bumble bee nest he had just found in his Iris's, a beautiful thing of carefully gathered straggly moss, with mishapen alien pods inside.