Er.. Usually a bouquet is just placed in the vase I think.. The vase should fit the bouquet and in that case it's not held together by anything but the vase itself. If you want to put something around them you could try using the Poser torus, adjust the "fatness" and Y-scale of it to make a broad, thin ring-like shape, then apply some satin/silk material to it.

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You just can't put the words "Poserites" and "happy" in the same sentence - didn't you know that? LaurieA
  Using Poser since 2002. Currently at Version 11.1 - Win 10.