I have created a 2x2 spruce tree farm in Feed The Beast and the trees won't grow at all. I have tried giving the saplings bonemeal and other things I found on the internet, but they still will not grow. Here's a picture of my tree farm:
This Minecraft Wiki article about trees might be useful. I assume you are trying to grow a Mega Spruce Tree (2 blocks x 2 blocks).
To grow a 2×2 mega spruce tree variant, there must be no block other than air, wood, leaves or saplings either directly next to or diagonally to the northwest spruce sapling.
You have a block that I don't recognize next to the northwest sapling. This is most likely the problem; try removing that block.
If that doesn't work:
Feel free to leave a comment below this post if you're still having problems.