I was asked how I take my plant portrait shots (flower/plant on black background). I just took photos of my setup, using my little snapshot camera, so I apologise for the quality of the pictures!
My camera is a CANON EOS 650D digital SLR. I bring the plants into my living room where I can get indirect light at a north-west facing window. I have a copy stand against which I prop a sheet of matt black mountboard, which is angled AWAY from the window.
Clipped into the camera holder of the stand is a steel rule, which can be lowered down to the pot surface if I need to show scale.