Lily of the valley will not flower
What to add to soil when Lily of the valley will not flower? I have hydrangea blooms beautiful, Hosta blooms beautiful in same flower bed. Gardenia grow great, though flowers do not last long but I think this is normal.
Lily Of The Valley may struggle in warmer growing zones.
Many people in warmer climates will grow them as annuals.
Here are a few links for you.