I have a bride that has requested a cake with hydrangeas separating each tier (similar to the one at the link below). I've never done this style of cake (though I'm excited to give it a try). I'm debating between using SPS with the multipiece legs (my tiers will be 4" tall so I'll need an extension for extra space) or sytrofoam dummies...which would be the easiest/recommended method? Also, how do I figure up how many flowers I'll need? They will be artificial blooms that the bride is providing, so I need to have a rough estimate of how many stems. Also, the cake will be a 6", 10", 14" all rounds. Thanks for all the help!!

http://www.kaboodle.com/reviews/hydrangea-wedding-cake

SPS makes a multi-piece column/leg. That's what I've used many times for this style cake.

Put you math cap on. The circumference of a round is d * pi. Figure the airspace between the 6" tier and the 10" tier to be 8" for a proportional look.
Therefore 8" * 3.14 = about 25"

Now measure the width of the artificial flower and compute how many you'll need to measure 25" across.

You have to do the next one yourself.

Thanks leah_s! Makes perfect sense!!