Moist but well drained soils are best. Bigleaf hydrangeas may wilt in dry soils but also cannot take soggy conditions for any period of time. Tolerant of a range of soil pH levels, however, soil pH will influence flower color.
Avoid pruning bigleaf hydrangeas, except to remove any dead wood. These hydrangeas cannot be cut back or trimmed at any time of the year without impacting the bloom for either the current season or the next.
Bigleaf hydrangeas benefit from a good layer of shredded bark mulch and afternoon shade, particularly in hotter climates. Apply a granular fertilizer formulated for flowering shrubs (like a rose fertilizer) if leaves start to yellow.