Sorry about the latin name thing...it's like my other native language (Horticulture..not Latin
), and I forget to use the common names sometimes.
Macrophyllas are the 'big leaf' hydrangeas, usually flowering in the pink to blue range, though a few are white. They are either mophead (round ball shape) or lacecap (row of large, sterile flowers in a ring surrounding a group of the small, fertile flowers to make a flat top). The leaves are big, bright green and shiny, usually quite fleshy.
I would say a good 2 foot (across) root ball would be great, though it will probably survive with less. Most roots are within 12" of depth, so if you can go a little deeper than that, you should be safe. I would prune 2/3 of the new, this-year's green wood off, and selectively remove a few larger stems right to the base if you can without wrecking the shape--if not, no worries. If you can, tie the rest of the branches up before trying to dig around it. Next Spring when you see where the buds for new growth are, you should take any extra dead sticks out, and prune back to just above the first healthy bud (from the top) on old wood.
Most important, make sure you re-plant at the same soil level, and make sure there are no air pockets around the roots. Water it in heavily and continue to water it 2-3x a week until you turn your hose off for the winter.
Enjoy!!
