Here's a lovely, messy craft for little kids - and the result does look a little like a thistle! How about making a class-full of these, cutting them out and using them to decorate the bottom of the notice-board with a field of thistles?
You will need:
Purple paint
Green paint
Paper
Instructions:
Paint your fingers purple and your palm and wrist green.
Press your hand onto the paper with your fingers stretched.