Linda From Maine wrote:
There are several ways, including placing a portable black board or cloth behind the subject.
I look for sunlit flowers or plants with dark shade behind. You need to understand how to set your exposure to keep your background dark and the subject from being over-exposed. I shoot in raw and do additional editing if needed for this look.
I also really like backlighting. The background of the below was a cliff face in deep shadow and I was shooting towards the sun.
Linda, the Hibiscus is stunning.