As you might know, this flower is called "Himawari" or sunflower and is one of the symbols of the summer in Japan. The Japanese weather satellite is named "Himawari", by which you can see how familiar the word "Himawari" is to the Japanese people.
The word "Himawari" is used as a season word in "Haiku" or an old Japanese style poem. Haiku was originated by Basho Matsuo, who was a famous poet in the 17th century. When one makes a Haiku, at least one season word should be contained in it.