Instead of spending money on flowers that will die in a few days, why not write your spouse/partner a love letter? Write about how it was when you first met and when you knew that you loved them and wanted to spend the rest of your life with them.
Talk about them as a parent (if applicable) and how you love watching them interact with your children.
Talk about your favorite things about them and how you love waking up next to them every morning and falling asleep next to them every night.
That's a gift that will live forever....long after the flowers fade.