"The Russell lupin, Lupinus polyphyllus ... is such a mild-mannered and quintessential cottage garden plant here in the UK and a complete thug in New Zealand," he wrote.
"Colonising stream banks, just like in the picture, they are taking over a habitat so important for New Zealand's unique wildlife ...
"The lupins that look so beautiful are actually a non-native, invasive species. In New Zealand ... their detrimental impact is huge.
"But on the positive side, the pretty landscape lupins create attracts tourists ... and they do provide a good food source to some desirable creatures, such as the long tailed blue butterfly, another non-native."
Blackhall-Miles isn't sure if the photo should have won or not. "What I do know, though, is that the photograph, as a piece of art, did its job. It made me ... look deeper at the garden that is our planet."