Is it permitted to water one's flowers during the 9 days? Or is this not permitted? What is the halacha here? Let me know, thanks.
Welcome to Mi Yodeya! According to the sefer Peninei Halacha (a resource I highly recommend) it is no problem.
Similarly, one may not plant anything that brings joy, like decorative trees, hedges, or flowers (SA 551:2). However, one may maintain a decorative garden, water the garden, mow the lawn, and continue regular maintenance.