I believe the flowers ... all of them, not just Bells of Ireland ... that are used in commercial bouquets are treated to prolong their fresh look. I know of at least one spray used to make flowers last longer. It's called Aquafresh, but I have no idea what's in it or where to go to buy it. Distributors of florists' supplies, I suppose.
"Isn't it enough to see that a garden is beautiful without having to believe that there are fairies at the bottom of it too?" - Douglas Adams