Many Japanese people go to the park to see cherry blossom. Actually, I went to a park near my house with my wife, and took some pictures.
During walking through the park, my wife asked me why Japanese people held parties below the trees of cherry blossoms. I've never doubted such questions, and couldn't reply the answers. I'll look into this tradition tonight!
Anyway, there are some shops, which sell junky foods like Banana with chocolate or sweet apples. They are often appeared in festivals in Japan, and then O-hanami seems to be festival.