I examined the bushes more closely and noticed that the larger non blooming bush is composed of mostly fresh green sprouts coming up from the base of the bush whereas the smaller blooming bush is mostly green sprouts coming out of brown (old) sprouts. Is there a way to prune them that will make them both bloom next year? The leaves on the non blooming bush are almost twice the size of the leaves on the blooming bush. Why?

First, with bigleaf hydrangeas you cannot prune to encourage flowering. Since the vast majority bloom on growth that was produced the previous season, pretty much ANY pruning will reduce or eliminate flowering, not produce more.

You have made some important observations. The fresh green sprouts of the non-blooming shrub indicates that most, if not all, of its growth is new wood. New wood - or this season's growth - has to mature or ripen to produce flowers next year. In zone 6, that happening successfully without offering winter protection to the plants is a bit of a toss-up. Most hydrangea gardeners in that climate zone DO protect or wrap their hydrangeas over winter and it is advised for all the macs that don't bloom on both old and new growth, like the Endless Summer or Forever and Ever series.

The one that is blooming is producing growth from old wood - the brown twigs and branches. That it is doing this without any protection may be attributed to its closer proximity to the house. A more protected or sheltered location or the reflected radiant heat from the house may be enough to protect the plant against excess winter cold.

Perhaps move the nonbloomer over next to the bloomer--that way they will both get some protection from the house. At least you wouldn't be losing more blooms that way.

Kate

The non bloomer is next to the garage which is attached to the breezeway that you see in the picture so it is also protected. The issue seems to be the pruning job that was done on the non bloomer that is causing it not to bloom. These plants were both the same and doing fine prior to the pruning.

I would guess that the pruning removed most of the bud bearing old wood-hence the lush non-blooming bottom new wood. Next year should be back on track....