The way it worked for me is I tell the florist the height of the pillars, the circumference within the pillars where a plastic florist thing can be set to hold the oasis (wet foam) and how far the flowers have to stick out --(the outside perimeter) to get that hanging over effect on the two tiers. The florist comes up with the set up. That oasis stuff (wet foam) can have formaldehyde in it and I prefer to leave that between the bride and the florist.
And that might be lily of the valley which is not at all edible to a poisonous degree.
And I would do it the same way if I couldn't stick the florist with it ;) Shop where I could buy the plastic dish dealio
And since you've got some cascading there too I'd get some fresh flower spikes
Hey are you in North Mississippi???????