If you use felt or some other material for your background that has a texture to it make sure the background is far enough away from the flowers so it is out of focus. Otherwise the texture may show. Be sure your camera is reading the flower for exposure. If the black background is to prominant the camera will try to turn it grey making the colors in your flower was out. You can easily over ride the settings on your camera to compensate for the exposure.
Try to stay away from direct flash if you can. I like to put a light source to one side slightly in front and shine it through a thin white cloth or plastic material. Doing that will really difuse the light giving it a soft look. On the oppostie side put a white card that will reflect light back towards the flower. You can move the card closer or farther away from the flower to control how dark the shadows will be. If you need you can bounce a 2nd light into the card and onto the flower. Light works like a pool ball on the table with no english. It will bounce off the card at the same angle it hits the card. You can also place a white card just below the lens of your camera to bounce light straight into the flower. It doesn't need much so the spill from the other lights should be enough. You can tilt this card back and forth and see how it changes things. All this should give you a nice soft light. If you decide you want more shadows you can use a black card to one side. It will act to absorb some light from the flower on the side nearest the card.
If you are lucky enough to have a garage or a covered patio that has a large opening to the north you can take advantage of that. Get basically anything large and white that you can find. Bounce the sunlight into the garage and you will have a really nice light. It is just a matter of placing the flower and camera to take advantage of the light. Again you can bounce more light to one side with a card if you need.
I really like bouncing light off of cards and onto the subject instead of pointing the light at what I am shooting. Just moving the cards can give you all kinds of different feels and it is much easier than moving lights around.
