Conversation

Begonias are forest floor plants and some are highly specialised for low light conditions. In the darkest places, they have metallic blue leaves.

The colour comes from iridoplasts – a special type of chloroplast for capturing as much light as possible. They work by having many tiny surfaces which absorb light. An accidental side effect is that any light that reflects back gives the leaves an iridescent blue sheen.

A similar reflection effect causes the blue colour in Morpho butterfly wings.