Salem

Why are the berry bushes not producing any fruit?

They have already been picked clean, and have some random game mechanic for the regenerating berries. Just forget about them for awhile, and eventually there will be more berries on the bushes.

Many of the bushes around me I picked like a month and a half ago, still no respawn... So try not to count on them for the stuff you need, or just walk farther away and find some unpicked ones.

can the same be sade for maple leaves?

Leaves around me have all respawned in the same amount of time, I have no real idea on the mechanics but just from observation I'd say they have a higher respawn rate. I still believe it takes at least a couple of weeks though.