The Mayflower under the moonlight.
When the atmospherical pressure start to go down, the plant begin to stress making it blossom, into the beautiful picture below.
(wikipedia)
The same process repeats in different plants, e.g. The cannabis plant, she needs to be polinated in order to breed; when you isolate it from the male plant, she creates the flower in hopes to interbreed, which after processing is what we smoke, If the plant fails to polinate, she makes the perfect flower without seeds.