Looking To See was wondering what in nature is blue.

That had me looking through my snapshots - a lot are untagged so it is never a completely pointless exercise, even if this thread strictly is. Turns out I have a lot of evidence of blue. I'll update this when I feel like it, and other members should also feel free to add their photos (but not stuff from the web, that would spoil it). Please correct any IDs as appropriate. 

Right. Some of the commonest blue things in nature are flowers so here's for starters...