Hmm, how to answer that.
The contest is going to be judged on the floral content, not the background, but the background could add to the floral content. How is that for an answer!
OK, example might work here.
In the following image, the focus is clearly on this single red rose. Yes, the HM is in the background but it is the backdrop to the rose. The rose is the picture.
However, in the same area and at the same time. I also took a picture of the single red rose from a different angle. Yes, the rose is still there as are lots of bushes and a couple trees BUT the picture is most definitely about the Conservatory on the HM building.
So, do you see what my answer means now. What will draw the viewers eyes. In my first picture the first thing the eye focuses on is the rose. In the second picture the first thing that draws the viewer in is the building. That is how you can tell if your picture will make the grade.
If still confused, post it or PM it to me and I will give you an opinion.
RU