I usually sprinkle my leftover grain mix' in my town wastelands but I don't look for mesurable result.
I do it when I go for a walk, where I walk and I see that nature is a bit wild. Like in the places that have a bit of wild herbs not cut or remove. I don't care much about the time of the year best to the plant either.

This way, I usually see some flowers from flower mix' the next year. And once I had a few tomato grains that I sprinkle on top of some dried sewer mud and I had actual tomato fruits on it almost every year until the wasteland was repurpose.

Nature does not need much human intervention to grow. But I'm sure that with more care, I could get some better result.