OP did say how to make them in creative, so I'm assuming he means without mods. But those are still good tips.

Anyway, one method I use to make trees is just starting out with a 2x2 base, building up, and placing leaves on each side, filling it out where it looks good. If I want a really big tree, I add branches using the sideways logs and just make them go in random directions, then cover the logs with leaves. From there I just fill it out again, so it doesn't look too sparse.

this youtube video has big birch trees made by emosnail
http://www.youtube.com/watch?v=6pPAs-98 ... x&index=39
wanted to try to make them. I have single player commands - maybe they can help?

Gather a whole lot of saplings then, just put them side by side like in a square shape like 4*4 (16) then wait...BAM huge tree.

This is TOTALLY LEGIT. Put fences around a sapling and then bonemeal the sapling. It will force it to grow big. Unless you are meaning HUGE trees, like the one's that people build, this is the legit big tree.

I think you would have to build them, unless there's a mod, but I don't know of one.
If you have your own server with WorldEdit, you can generate big oak trees, but I don't think you can generate big birch trees....



If you place saplings in a 2x2 square, like with jungle saplings, you can grow each one with bonemeal and make a tree that's sort-of big. Can be bigger than 2x2. They won't work like jungle trees though, because with jungle trees you only need to use bonemeal on one sapling in a 2x2 circle and it's a lot bigger.

World Edit.

place saplings side by side use bonemeal to make each sapling grow boom big trees