Actually, bigleaf hydrangeas tend to bloom quite precociously - even first year cutting grown plants can produce flowers. So I'd say it was less an issue of establishment - although that can certainly help - but rather one of climatic conditions. Cold winters or late spring frosts can damage latent flower buds, resulting in a lack of flowers. And with rebloomers (like Endless Summer), some time to establish DOES encourage better flowering, at least from the new growth, which tends to be more prolific in its production after a couple of seasons in the ground.

In a zone 5 garden, winter protection for any Hydrangea macrophylla cultivar is suggested to ensure reliable flowering. Same for zone 6. You are only completely safe without winter protection in a zone 8 or higher although most years zone 7 is fine without as well.

I've found Macs grow fastest/best in moist, DARK (organically-rich), well-tilled soil with adequate drainage. The sooner they get into this, the better off they'll do. To speed up the process, use lots of bark mulch yearly and don't worry about continually raising your beds too too high because they will compress down with decomposition and settling. Effectively, once you have a nice swollen organic mound about 1 foot deep, this will be the breadbasket for hydrangea root expansion, as they like being near the surface. Most places have more or less solid clay after about a foot of depth, so you see what I mean. Luis actually turned me on to a process called "mound layering" which works great. As the soil settles and you can see woody clumps of crown plus some roots ON the surface, add 2-3 inches of mulch and soil on top of the crown every year or two (around October/November), going 2-3 feet out around the plant. This will give more organic soil for the plant to expand into, plus it will protect the crown and new cane buds nicely during harsher months. You can also go in a ring beginning 18+" out from the outermost canes and till in some fresh topsoil to a depth of 1 foot (and tamp back down), which will effectively expand the original hole you dug to plant the hydrangea, once again making room for more root expansion. The bigger the root system, the thicker and longer new canes will be, and hance some bigger and healthier flower heads.

Thanks for the info guys. Springwood, every year I purchase about 50 bags of manure and compost and top all my plants off with a nice deep layer of this then topped off with cedar bark mulch. I think I will bury the hydrangeas with mulch in the late fall to protect them over the winter.

Awesome idea. And feel free to fill some of that in around the root balls come spring. They should grow fast and mightily, especially the middle of year two after planting!