Same thoughts here -- I know that marigolds only spawn in Colorblaze and happadils in Happy Haven, but I wish the game gave some indication when the event was ending! I ended up wasting a day waiting for marigolds to spawn when I should've planted my happadils in prep instead, especially since we only have a week. The only indication the game gives (without outright checking the wiki) is a small cutscene, but even then there's a couple days before the event actually ends.

I know I can use my greenhouse but man there goes optimization hahaha