Miracle Gro Liquid takes effect faster than general purpose slow-release fertilizers. Generally speaking, general purpose slow-release fertilizers are what you need with hydrangeas since they are not heavy eaters and will not respond to lots of fertilizers. Matter of fact, too much may increase nitrogen levels and make the shrub stay green and produce fewer or no blooms. For weddings, I always suggest having a florist take care of this. Weather is too unpredictable and you do not have to worry about how big or small the blooms are, why pests are suddenly eating the leaves, powdery mildew problems, etc.

I don't mean to be flip, but there's no perfection in gardening. Those blooms will either look nice or they won't. I don't know why/how fish emulsion would effect blooms that are already set.

Actually, the best way to get the best blooms on the wedding day is to buy the plants from the florist a day or 2 before. They know how to coax those blooms and deal with any issues.

The previous post is very much on point :-) There is no way to ensure the plants will be in flower on that specific day - only climate/weather and the natural bloom cycle will determine what happens. Fertilizing - as appropriate - will not guarantee a flower will appear on a particular schedule. At best, it can only help to encourage the formation of flower buds.

Hydrangeas that are forced into bloom - i.e., florist or greenhouse hydrangeas - have received a very highly controlled program of heat, light, growth hormones and fertilizers......something most homeowners are not able to provide.

Actually, most florists would not know how to coax blooms to perfection, they buy them that way from greenhouses who do know...:) Many florists don't know squat about plants.

former florist who was an exception to that rule...