After a bit of discussion and deliberation I know it's a turnip not because i ate some (although i did have a tiny nibble - it was tasteless) but because i asked my waiter.
So much effort must go into these gorgeous garnishes i only wish they tasted good too, then the hours of prepartion would be even more worthwhile!
Have a look at this site and learn how to make you're own http://www.finedinings.com/Garnishes.htm It beats a sprig of parsley any day!
p.s. My favourite is the courgette flower - simples!