Parsley is notoriously difficult to grow from seed: I find that it either fails to germinate or else comes up in a thick forest. Sometimes it seeds itself in the oddest of places, making me go to all the nooks and crannies of the garden when I need some. I generally find it a lot easier to start off with seedlings purchased from our local nursery. I mostly grow the curly variety, although I once enjoyed a bumper crop of flat-leaf (also known as Italian) parsley that mysteriously appeared in our garden in the months after the house next door was built!
I use parsley almost on a daily basis and so make sure I have a ready supply of it. My only encounter with parsley as a medicinal plant was when I was a university student. The nursing sister in charge of the sanatorium brewed me a large mug of parsley tea to ease the pain of a kidney infection. When she picked a large bunch of parsley for me to brew some more in my room later on, she told me that parsley is both a tonic and an immune booster. It is well-known, I think, that chewing a sprig of parsley can help to neutralise the smell of garlic on one’s breath.