It was indeed meant to be so, I hoped that that would make it more interesting.
Also, the centers are not that off right? The trunk leans to the left, that should balance it a bit.
There is a 3 px difference, see this image

http://img367.imageshack.us/img367/9703/tree003bz1.png

The red lines are the centers of the base and the leaves.

http://products.pixelmill.net/themes/jimg/leaning_tree.jpg

Yeah, what Darth said. The left side of the tree should have more foliage. Right now it looks to be leaning. Unless of course you meant it to be that way. Otherwise it looks real nice. Love your dithering style.

I am a tree. Tree tree tree. Goody for me.

Nice use of texture on the leaves, but the shape seems pretty lopsided rather than natural, and the trunk could definitely use some added attention. It looks smeary. Good job though.

The foliage of the tree is off-center of the trunk is, I think, what he meant by that.

The dithering on the foliage is cool though, I like/use that style myself!

What symmetry do you mean?

The tree is nice but the symmetry seems off to me.