I hate it when I bonemeal a sapling and I get a lollypop tree; why would I want them to spawn naturally? I suggest that they stop these giant weeds from spawning naturally, they take forever to chop down and i'm always afraid mobs will spawn underneath them because they block out to much of the sun. I just want to easily chop down a forest biome so I can have a plains biome with less weeds more flowers and more interesting terrain; my Minecraft world is running out of pre-1.9 forests.
Are you talking about big oak trees? They are supposed to give more variety to otherwise bland forests of the same tiny trees; it'd be better if there were more large trees, for example:
An entire forest made out of, you guessed it, big oaks (this biome was my memorial to their removal in 1.7. They aren't that dark on the ground since I modified the lighting calculations in these biomes to reduce the amount of light that leaves block, mobs do still occasionally spawn but that's just part of the game, Mojang even mentioned daytime mobs as a danger in roofed forests):
A forest of even bigger trees that can reach the clouds from sea level - the biggest ones can have more than 500 logs and 3000 leaves; like real forests there is also an understory with smaller trees:
My version of a "mega taiga", with trees that really are mega, with 3x3 trunks and as many as 600 logs each:
A forest with multiple types of giant trees:
All of this came from a single tree - 5 stacks of wood, a stack of saplings, and 8 apples (around 1200-1600 leaves, some of the saplings probably despawned before I collected them from the ground):
Many people even didn't like it when Mojang removed them in 1.7 because of "lag" (aka Mojang's awful code, which started becoming much worse at that point).
As far as preventing them from growing, you can put a roof overhead (use some block other than dirt or logs, which they will grow through); 10 blocks (9 below the roof) will allow the player to harvest any trees that grow, including the occasional small big oak:
https://minecraft.gamepedia.com/Tutorials/Tree_farming#Oak_tree_farming (caution - this is badly outdated as it still says that trees can grow through bedrock and replace many other blocks, which was patched years ago. However, I don't think they have changed the basic growth mechanics of trees; as mentioned 9 blocks of space allows for 7 blocks of trunk, which the player can harvest from the ground, plus one more if you stand on the stump, so 11 blocks (10 below) would also work).