I have an order for cakes that have a woodsy, rustic theme and I plan on placing 2 rosemary stems criss-cross on the tops of the cakes (chocolate, vanilla and lemon cake with buttercream). Sooooo...with rosemary having a potent scent, will the rosemary 'flavor' seep into the buttercream?  I've seen rosemary on lemon-rosemary cakes and the like, but don't really want it to seep much into the chocolate and vanilla). Anyone have experience with this? I advised the customer to place it on very last minute but just wanted to double check with someone.  Thanks!

The essential oil in rosemary is really strong, so yes having the client place the stems on at the last minute is good advice. Just touching the leaves leaves a scent on your hands, so I'd imagine it will rub off slightly on the buttercream. 

You could sugar the rosemary, but it would give it a wintery icicle look. 

Thank you, thank you!