My Endless Summer Hydandeas are getting very large with beautiful leaves but not blooming. I have not treated the soil for a specific color as any will do! I've read sometimes too much, too little or dappled sun can be a problem. Should I just move the plant and see how it does in another place? When is the best time to move it? Thanks!

If these are the common mophead type, Hydrangea macrophylla, the most common reasons for non-flowering are:
1. damage to the flowering buds from winter cold or late freezes (not really appropriate for remontant or reblooming cultivars like Endless Summer).

2. Pruning too much or at the wrong time.

3. Fertilizing with excess nitrogen (like with a lawn fertilizer) -- this will push foliage rather than flowering.

4. Excessive shade.

My standard recommendation for those located in zone 6 or lower is to provide winter protection for macs and to avoid pruning as much as possible. And if you go through previous posts or the archives, the performance of 'Endless Summer' in particular but also various other of the reblooming or old wood/new wood bloomers seems to be sporadic at best. While many of these cultivars are reputed to have increased hardiness and many skip protecting them in winter, they will often die back to the ground annually and seem to take most of the growing season to regain size and leaf structure at the expense of producing many flowers. IME, 'Endless Summer' is not nearly as "endless" as the breeders would like us to think :-)

A rich organic soil, on the acidic side, and morning sun/afternoon shade is the ideal situation for most hydrangeas. And sufficient water during the growing season.