No, not leaves. (Just in case you were thinking of doing that, this is poison ivy.)
No, I'm talking about cotton knit fabric. If you're running out of toilet paper and can't find any anywhere, use a twelve-dollar bag of cotton painter's rags from Lowe's. If you can't make it out to the stores or are short on cash, cut up a couple old t-shirts. Those are about the exact same fabric and work just fine, too.
Turns out it's a lot more comfortable than TP! Easy peasey to wash, too. And my rolls of tp are lasting me well over a week now. Almost two.
I don't do the cotton fabric for Number Two. Even I, with my iron stomach and lack of squickedoutness about "nature", don't much like the idea of washing that. But for pee? Sure. Why not.
Contrary to popular belief, urine ISN'T sterile, but it's also not full of pathogens like feces. And so long as I keep them washed on the regular, there's no smell at all.