When the father of a very good friend was confined in the hospital, my sister who works as a doctor there advised me to bring flowers when I go to visit. I asked why. She confided that flowers seem to have a magical effect on most of her patients as they responded positively to these, often enabling a speedy recovery.
I told her that flowers have pollen and they might not be good for people who are sick. She said, yes. But still she continues to notice how a room with flowers changes the otherwise dreary atmosphere of a hospital room, mysteriously lifting up the spirit of the melancholic or ailing person.
No wonder flowers are used for special occasions like birthdays, valentine's day, anniversaries, and most rites as they do not just show how we appreciate the person, or reveal how we try to beautify the room, but I guess it's more on hoping that something positive will come out of the occasion.
Just don't overdo it. The room might look like a funeral parlor. Or otherwise make the person feel that he/she should open a flower shop.