The only current purpose of Rubber Trees is for their Rubber Wood (RedPower2) which differs from IC2 Rubberwood in that it can only be crafted into sticks or Rubber Wood can be fed to an Extractor for Rubber.
*This can be crafted in the Player's 2x2 Crafting Grid.
How to Grow
To grow a Rubber Tree, you need a Rubber Sapling (RedPower2) at the center of a 3x3 square of dirt. It is advisable to place torches close outside of this 3x3 square to allow growth to continue overnight. You don't need a 20x20 grid of clear space around the trunk of the tree, but growing it too close to anything might impede its leaf growth at higher levels. You do need free space above the tree (at least 10 blocks, advisable to have clear sky above it).
Its better that if you want to build a massive tree house that you plant more than one tree at a time.
Since Rubber Trees take real-world hours to grow, it may be beneficial to bury a Dimensional Anchor below the tree to keep the sapling loaded constantly. It is most useful to plant the sapling in the center of a chunk, then make the anchor set to keep only that one chunk loaded. When the tree does eventually grow, it will load as many chunks as it needs, then unload them because of the lack of nearby players. It is also advised to remove the anchor after the tree has grown to prevent lag build up for other players.
- You can not use Bone Meal on these trees to speed up growth.
- Player planted trees do not seem to grow as high as a naturally occuring version.