Zucchini in weird places!!

I found some zucchini growing down near a fence that has fallen and its growing some nice zucchini. I have some growing in my garden and they are not as nice as the ones near the fallen fence. Strange? I don't water them like my garden and they are nice and good tasting. Question is, cause I've been gardening for years, why is that zucchini growing nicer than the ones in my garden. lol