This has maybe always been this way, but I just noticed it today.
I plant my garden. Sometimes I water it before I leave for good measure, even if the cells are already dark.
I am rewarded for watering with little gifties, moreso since I reached Level 5 skill with the gardening.
Turns out, I can keep watering and watering and watering those poor seeds, and keep getting tickets and musicboxes and food, for about as long as I have patience, I think. (Though it turns out that my patience is on the low end for this activity, so I didn't keep at it more that a few repetitions.)
I suppose it could be good to just prevent the unneeded watering, like with the trees... or you could make the seeds die, too.
And maybe this all goes away when the legendary new gardening interface is revealed!