Maybe it's not in enough sun..... maybe more sun makes more scent.... ?????

Violets (and most flowers) smell stronger when the air is warmer. Bring the violet flowers indoors and the smell will appear.

Here in Ottawa, Canada, the smell of the pink and purple scented violets is the first "smelly" of the year. But, I have to get down on my stomach and put my whole face in the patch and inhale deeply! It is worth it, though at the time it is very cool here.

I don't think it is as simple as needing warmth. I don't know a better answer. I just know I used to think that, but I have found numerous occassions where it does not seem to apply.