Hydrangeas are a genus of 70-75 species of flowering plants native to southern and eastern Asia (China, Japan, Korea, the Himalayas, and Indonesia) and the Americas.
Most are shrubs 1 to 3 meters tall, but some are small trees, and others lianas reaching up to 30 m (98 ft) by climbing up trees.
They can be either deciduous or evergreen, though the widely cultivated temperate species are all deciduous.
source wikpedia
So can rabbits eat Hydrangeas at all?
Unfortunately, they cant eat them at all. Hydrangeas are poisonous to rabbits and will harm them if they are eaten.