Only the big redwood trees, the ones you can't harvest. Each tree has 8 spots, 4 on top and 4 on bottom. 1 Sap per ~11min on official (I think?), will distribute 1 to a single tap iirc. Max 30 sap held at a time per tap. Multiple Taps only benefit in how much sap will be stored in total at a time, and will not change the rate of production.