Most of our pansies are in shade most of the time. The ones I photographed are in full sun, and were miserable their first few weeks (while their siblings went wild in the shade). And then some switch got thrown and BANG! Blooms! Because… <sigh> Dunno.

Under the most carefully controlled conditions of temperature, humidity, and soil, a plant will do as it damn well pleases!

— sign spotted at a commercial greenhouse