Photography tip that I recently learned: Easiest way to get a black background is to take the photo at night, making sure that there is a large distance between the object and any wall behind it. If the flash is unable to reach the wall, then you have a dark background. Final adjustments done with rawtherapee can make it completely black.
For this photo I placed the potted plant on a table and then aimed the camera towards the longest corridor in my apartment (which is not very long).
The flowers have since produced seeds, and some of these seeds are seedlings at the moment. One of the seedlings is a mutant with three embryonic leaves instead of two (a tricot)!