If he got them at a local nursery, they probably are a variety that will survive your winters. They will lose their leaves for the winter, and grow back in the spring. If they are a "macrophylla" variety, DO NOT prune the "dead" branches after the leaves fall off. This type of hydrangea blooms on "old wood" the next spring. Shrubs that are planted in the fall usually do just dandy--be sure to water them for the next few weeks, too. Good luck!