Sometimes things come together nicely. Last week one of my sisters paid me a visit and I told her about my nightly torchlit forays to hunt for slugs and weevils. A couple of days later an Amazon parcel arrived, containing an LED head torch.
I often look at plants for sale online. I had been looking at Begonias and came across a reference to some of them being iridescent when lit by torchlight at night. Having more than a few Begonias, on my second night of hunting with my new light, I ventured into the greenhouse and turned it on Begonia Cool Breeze ‘Emerald’. I’m not sure what I was expecting but bright blue iridescence so bright it looked light it was the source of the light wasn’t it.
Going round the garden in the dark, I turned the light on several other Begonias and while none matched ‘Emerald’, several showed the phenomenon to some degree. The explanation for it is to do with catching the most light in the very low light environment of a forest floor and the less light the leaves receive the more iridescence they show. Thus it shows more on leaves beneath the plant’s main canopy, or on ‘Emerald’, the leaves at the back of the plant which is under a bench and lit only from one side.
I took pictures of ‘Emerald’ with my iphone and using flash. In the pictures it looks much as it did with the head torch.
In the garden I took a picture of Begonia palmata ‘Tie Dye’. It was only markedly iridescent on leaves below the main canopy. It is growing in a shady area where it gets no direct sunlight but it is not in deep shade.
Not for the first time, I am blown away by the level of accomplishment that plants display vis-a-vis photosynthesis.
Here a couple of links to further explanation of this phenomenon.
http://www.esalq.usp.br/lepse/imgs/conteudo_thumb/Behind-This-Plants-Blue-Leaves-Lies-a-Trick-of-Quantum-Mechanics.pdf
https://www.jungle-leaves.de/the-secret-of-the-blue-leaves-iridescence-and-structural-colors-in-plants/?lang=en
garden ruminations 
Jim, this is totally fascinating. Now I’m wanting to go out with a torch tonight and explore my Begonias to see which ones will glow in the dark! The iridescence is dazzling. (I wonder whether Terra Nova took that into account in naming ‘Emerald’?) I’ve noticed that those with silver leaves still perform very well when tucked away somewhere in the shade. Now you’ve helped me to understand why. Thank you for this beautiful piece of botany this morning!
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It seems to be the ones with a velvety rather than glossy surface that do it, amongst mine at least. I’m interested to know what you find.. I must look at Terra Nova’s info on ‘Emerald’ to see if iridescence is even mentioned.
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That’s amazing.
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What a lovely find from a generous gift.
Have you deleted your Twitter account? I couldn’t find you when I went to share this post and tag you. I thought I’d check as there is quite a lot of #SixOnSaturday posts on there each week.
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I’m no longer on Twitter. The logo change provided the last small push but it’d been on the cards for a long time.
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Very cool! We learn something new often when we garden!
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So true, and a key reason it’s so engaging.
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Brilliant. The success of begonias in low light contributes to their success as house plants.
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That’s pretty amazing!
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Very interesting…I might need to try this .
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