It is unclear which type of hydrangea you are referring to. You could plant a climbing hydrangea if it has a rough wall surface to climb with its aerial rootlets; no trellis needed normally (use it on smooth surfaces) but you may want to periodically monitor growth and forward it towards a direction that you approve of. You can also plant a standard panicle hydrangea that is grown as a tree. A Grandiflora or Limelight panicle tree, for example, would grow above your windows and well into the attic at maturity. If you ever use a trellis, ensure it is not made of wood as climbing hydrangea can exceed 80 feet high or wide and will grow for decades, well above the life expectancy of a wooden trellis.
