I have been trying to grow 2x2 spruce trees in a forest with no success, and yes, I do have 4 saplings in a 2x2 shape. I haven't tried bone mealing it at all, but I'm wondering if I moved to a biome where spruce grows naturally, will big trees grow without bone meal if I put the 4 saplings in the proper arrangement? Also, will the big trees grow in a forest with bone meal?
Bone meal just speeds the process up a lot. It's the equivalent of delivering lot of block ticks really fast. They have to go through 2 successful grow attempts to become a tree. Bone meal is said to give the tree a 45% chance to get to the next stage, so 4 bone meal should often do the trick. Sometimes I have to just keep splatting it for a while though.
Block ticks try to make a tree grow (advance to the next stage) but they often fail (6/7).
Trees need to be on dirt and to have enough free blocks in the right places and have light. Biome doesn't count.
It doesn't matter what biome you are in; trees will even grow in the Nether, one of the last places you'd expect a tree to grow in; and their growth rate only depends on the block tick rate (which can be altered with the gamerule randomTickSpeed) and a random factor when bonemeal is used (saplings have two invisible growth stages and bonemeal has a random chance of working. When bonemealing a 2x2 tree only use it on one sapling so it advances through the growth stages faster).
If a tree isn't growing the most likely problem is insufficient space; oak trees are very forgiving but not so much for some other types of trees, which won't grow even if there nothing that would get in the way of the trunk or leaves. For example:
2×2 spruce trees require a 5×5 column of unobstructed space at least 14 blocks above the saplings to grow (15 blocks including the saplings themselves). This column is centered on the northwestern sapling. A 3×3 area is required at the base of the tree (the level of the saplings).
Ahhh ok!!! Thats what I was doing wrong, I had torches right next to the saplings.
Thank you everybody for your responses, they were all helpful
Torches should be okay if placed one block away, I've never had a problem with them. If you want them to grow reliably they need a source of light for at night or they won't grow when its dark. Many times in my farms I will put jack o lanterns, glowstone or sea lanterns in the floor for lighting so I don't have torches sticking up that I can hit accidentally when harvesting.