Hydrangeas has two meanings in the language of flower. The flower was seen three times: twice mentioned its name by Kai, once shown at the end in which the mother was narrating.
One is the coldness/heartlessness and this represents the mother's hatred toward Richard or dissatisfaction caused by Kai at the beginning of and the middle of the movie.
Another meaning, is the giver's appreciation for the receiver's understanding: "Thank you for understanding." At the end of the movie where the mother and the flower were shown together, the flower tells the change of the mother's feeling and now the mother accepts what she faces. Thus, you might sense Kai's appreciation.
This sounds sort of distorted but I like to stick to this idea because it is simply beautiful.
Hope this surprises you.
One is the coldness/heartlessness and this represents the mother's hatred toward Richard or dissatisfaction caused by Kai at the beginning of and the middle of the movie.
Another meaning, is the giver's appreciation for the receiver's understanding: "Thank you for understanding." At the end of the movie where the mother and the flower were shown together, the flower tells the change of the mother's feeling and now the mother accepts what she faces. Thus, you might sense Kai's appreciation.
This sounds sort of distorted but I like to stick to this idea because it is simply beautiful.
Hope this surprises you.