The two are not related.
"Under the umbrella among flowers" is a word describing a poetic scene, which means a place where flowers are blooming and the scene under the umbrella. This word often appears in ancient poetry to describe beautiful gardens or flowers.
"Double Ninth Festival" is a traditional festival, also known as the "Double Ninth Festival", celebrated on the ninth day of the ninth lunar month. The Double Ninth Festival originated in ancient China and is a festival that emphasizes respecting the elderly and praying for blessings. People usually climb high, admire chrysanthemums, wear chrysanthemums, drink chrysanthemum wine, etc. to celebrate the festival.