I recommend using Gorilla Glue. There's nothing better. You can purchase it at Wal Mart. Good luck. Your flowers sound pretty.
I agree with Janice, E6000 usually works well and letting it sit a few mins, putting on both pieces and clamping it can really make a difference. Another options that people recommend (but I've never used) is Loctite Glass Glue. Wishing you the best!
E6000 Multi-Purpose Adhesive
Hi Angela: You can try Locktite Glass Glue or Amazing Goop 170011 Marine Adhesive. Here is a site that I found that may help you out. https://empressofdirt.net/glue-outdoor-garden-art/ Just about any marine glue should work, but check the site for more information. Good luck with your project:)