How do I enter the competitive portion of the Flower Show?
You do not have to have a sponsor but you will need to read the Exhibitor's Guide for this year's Show. It is now on the show web site and available for downloading.
You don't say if you are planning to exhibit in the horticulture classes (plants grown in post) or in the artistic classes (arrangements, pressed plants, etc.) Reading through the guide will give you the information you'll need to enter.
The exhibiting at the Flower Show page is very useful; please read it carefully.
In the meantime, if you have questions, please contact firstname.lastname@example.org
Hope this helps. Good luck!