I use a flash (or two) for flower shots. And by using a small(ish) aperture and fast(ish) shutter speed, the background is naturally under-exposed and comes out dark. Choosing the subject with clean background also helps. If there are bits in the BG you can see, a bit of Photoshop work will cure it. :)
Beautiful capture. May I ask how you were able to get that black background? I have a lot of orchid pictures and want to place a black background in Photoshop.
