Is it "the" good?

In French, but not in English :-)

Hmm, I know what you mean. It depends on whether it is a general statement, or relating to a specific context. For example in the following statement it is talking about the ecological impact of birch trees.

"Some of these nutrients are returned to the surface of the soil each year when the leaves fall in the autumn, thereby becoming available for other organisms in the forest community."

It is "the leaves (of the birch)"

In a general statement there would not be a 'the'.

"Birds nest in the spring, and leaves fall in the autumn."

Anyway, I think it would probably be best without a 'the' here.

(well I meant "the" autumn XD, but oki^^ that's good)

> well I meant "the" autumn XD

Oh! I didn't think of that. I think either 'the autumn' or 'autumn' is OK. Although it's more common without than with.

And we're back to the "do you need a 'the' or not?" English/American difference...

> Also, Google, "in the autumn" gets many more results than "in autumn.

Not if you Google "leaves fall in (the) autumn".