Orn -
Many people use black velvet as a backdrop because it "absorbs" the shadows and provides a cleaner view of the tree. The cardboard may reflect light and provide an unwanted glare in your photo if you use flash. You can also set-up with several lights and play with them until the shadows are minimal.
Another tip: The angle of view should not be too high. Try not to show the back rim of the pot.
Here are a few links to get you started:
Photography set-up link
Picture taking tips
-Candy