Mums are sun worshippers. They need six to eight hours of direct light daily. If your plant lives in shade, it stretches like a teenager trying to reach a snack. It gets leggy. It flops over. It looks pathetic.
Move your potted mums into the brightest spot you have. Even a few extra hours of morning sun makes a huge difference. For in-ground mums, trim back any tree branches hogging the light. They’ll sulk for a day, then explode with growth.
Chrysanthemum Care for Fall Blooms and Rebloom | Leafy Zen
Fun fact: Mums are photoperiodic. They sense shorter days and lower light to set buds. That’s why they’re fall’s natural clock. So don’t mess with that—no bright porch lights at night. It confuses them.