From 831 cherry blossom banquets became an annual event at court, and as the Heian period deepened 'hanami' came to refer only to sakura.
As cherry blossom parties became fashionable amongst the aristocracy, 'hanami' began to appear in works such as 'The Tale of Genji' (源氏物語).
"Yes, the cherry trees put this truth very plainly: none of the glory of blossoms and autumn leaves lasts long in this fleeting world."
-Murasaki Shikibu (紫式部 ? 973-1031?).