I planted my hydrangea tree last year. I bought it from a place where plants can be purchased for pennies on the dollar compared to nursery prices. The down fall on buying like this is the plants are dormant. Almost no root, and need to be rinsed well and brought back to life.
Any way I planted it in a large well drained pot last year. Finally in mid to late Augast this year it started blooming. I transplanted it in the ground tonight. The trick to growing in pots over the winter is "Good Drainage" with out it your plants roots rot out. I am in growing zone 5a.