I've build a multifarm:
However, when I right click the farm blocks no GUI appears… So how do I access it?
Minecraft – How to access the multifarm GUI
minecraft-feed-the-beastminecraft-forestryminecraft-java-edition
Related Solutions
Since the pack has MineFactoryReloaded, I would look into using the Planter and Harvester with MFR's rubber trees. The rubber should be interchangeable with IC2 Rubber because of the ore dictionary. You should also be able to use the harvester and planter with the IC2 Rubber trees, but I think that is less productive. On the other hand you'll produce lots of rubber wood which could be used as wood, or tossed into an IC2 Extractor to get more rubber.
I had the same problem. You have to click in the normal setting for Minecraft: OPTIONS, VIDEO SETTINGS and set GUI scale on large. If that does not work I do not know
Best Answer
Remove the dirt, the farm places humus itself.
The farm also has to be exactly four blocks high. The horizontal size depends on the size of your multifarm. All possible options can be found here.
Keep in mind that you have to constantly supply power and must regularly insert water, dirt and fertilizer. For maximum effiency it's best to build the stone bricks higher up against the farm center (not above the center though), so your machines for input/output of resources don't hinder treegrowth.