From my experience
Rabbits will have a taste of pretty much everything but there are many plants which are poisonous to them. The hydrangea is one of those ..
We have a house
Rabbit, her name is Miss Grace and we have no choice put to put her in a run as if she'll eat the carpet, the flowers will be no problem
Here's the list anyway ..
http://www.ukcompanion.rabbits.org.uk/plants.html