Popsugar Lifestyle Flowers Interesting Facts About Hydrangea 9 Facts Every Hydrangea-Lover Needs to Know 11 July, 2017 by Maggie Winterfeldt View On One Page Photo 1 of 1 ADVERTISEMENT () Start Slideshow Share This Link Copy ← Use Arrow Keys → 1 They Have Their Own Day Hydrangea day is celebrated on January 5, ironically when the flowers are out of season. Even if you can't snip flowers from your own garden, you can purchase some imported from a warmer region from the florist. Previous Next Start Slideshow FlowersGardening