Originally posted by Aku returns:

I only have two extractors and keep rotating them on the same roots surrounding my Mistlands base and very quickly had enough sap to make everything I need. Now I just farm sap for some of the food.

I play on a server with some friends and we ended up with two roots next to each other looking like pin cushions.

It depends how often you visit them, but seems like 3-4 extractors is the max in terms of production.