An issue for some new users is that they apparently can't plant when using their own backgrounds. This is because you have to define the plantable area: just make sure that Adam and Eve's feet are at diagonal corners from each other and you will be able to plant. If you put them on either the front or back corners, the plantable area will be zero, hence no planting.
Sorry if the instructions in the app don't make this clear. We are fixing the instructions and will have the newest build up soon. Should have a few more plants too!