You don't have to grow them, they spread on their own, you could place 1 and later there would be a bunch.
Yeah, that is loving annoying when you've been working in a chunk for a while, and you finally go explore some caves. Every single time I did that I found caves filled with mushrooms on EVERY DAMN SQUARE. That's not the worst part. The worst part is that EVERY SINGLE MUSHROOM IN THE TWO AND A HALF STACKS I FOUND WAS BROWN. NOT A SINGLE DAMN RED ONE. /rage
So yeah, Notch needs to change that a bit.
Edit: Have some cake Plasmus/Mogarf :D
