Fred. Different plants can be called daisy tree, do you know which yours is, for example is it Argyranthemum? If you're not sure, could you post a picture? I did a quick Google search for Argyranthemum and allelopathy (the term for when a plant affects the growth of another plant) and didn't find anything. I've grown Argyranthemum and I don't recall its having that effect. Could it be that the environmental conditions didn't suit the primrose and celandine (different plants can be called celandine too, just to compicate things)? Is it too hot and dry where they are located? I'm guessing you are in the UK?
Does the yellow daisy tree look like this?
