I have a bride who wants silk flowers cascading down the cake from the topper to the bottom tier.  If I were dealing with fondant instead of buttercream I'd have no problems.  However, I've dealing with a buttercream base.  I'm wondering if there is an awesome technique that someone uses to hold flowers in place.  Would I need to put floral wire and maybe straws into the sides?  I'm a little concerned about the structural stability of that on the cake sides.  Would melted chocolate secure the flowers to buttercream?  I use Indydebis buttercream which is a shortening based buttercream so it is a very stable base.  The bride is also lactose intolerant so I cannot use anything that has milk products in them.  Any suggestions?

I'd use drinking straws over the stems of the flowers, and white chocolate in the straws and painted on the backs of the flowers to provide a barrier between them and the cake. You can insert the biggest flowers first, them add the smaller ones without inserting them into the cake at all if you can prop them in around the bigger ones.