Stolen from a post on Tribe, by a woman called "Sugar"
" I have super short hairs (The longest spot is about 2 1/2 inches) and I use a couple of methods. I usually start by hot gluing the flowers to a piece of felt. The I make a little flap on the back to thread a bobby pin through. Then I backcomb the spot I want to pin it to and pin it in in a couple of directions. Also you can do the little flap thing and use an alligator clip. Or sometimes I glue them to the felt and them stitch a wig clip on the back and then do the backcombing and stick it in my hair. Those things hold on the the finest of fine hair. You can find them pretty cheap on ebay."
How to attach flowers to hair? - Makeup and Hair for Dancers - tribe.net