I have heard people talk about letting your kid run around outside naked while you're trying to potty train, and while I don't entirely understand how letting him pee on the grass accomplishes anything other than training him to pee on the grass, I decided not to argue with Alex a few weeks ago when he wanted to run around outside without any pants on.
I also let him pick out the rest of his outfit, and apparently he felt as if one should compensate for one's lack of pants by adding a hat.
The only way that I found the "potty training outside" method effective is that I was able to get Alex excited about the prospect of watering the bushes and trees, so at least he was able to recognize when he had to go and run to the tree in time to pee on it. At the time, I considered that to be progress.
Unfortunately, Alex didn't think that "watering" the tree was sufficient, so he decided to "fertilize" it, too. Yours truly had to handle the cleanup, and that right there pretty much ended our outdoor potty training efforts.
p.s. This incident occurred quite a few weeks ago. Since then, A has taken great strides when it comes to going "pee-pee on the potty". He is now able and willing to pee into the pot whenever he has to go, and he can keep his "big boys" (aka big boy underwear) dry all day. "Poo-ing" in the potty has proven to be more of a challenge, but we are confident that he'll catch on...eventually. 'Til then, we decided we'll just let him out to do his business in the backyard like Murphy so we don't have to change dirty diapers.