Lettuce is one of those vegetables, that once it gets contaminated with bacteria, you are kind of screwed. You can really wash it off and lettuce is usually eaten raw. Having it grown in a pile of manure may make it harder to keep from being contaminated.
I hope you don't buy organic vegetables because have I got some news for you... Between copious amounts of manure and liquified fish as fertilizer, you could always tell by the smell which farmers were looking to cash in on organic produce.
Why would anyone fertilize their crops right before harvesting them for sale? This makes literally zero sense, as it would just be throwing away money. It's like the urban legends about people lacing marijuana with 100% pure cocaine or whatever.
That was neither said or implied.
"Horta" is any green leaves you like, blanched and served with oil and lemon. Sure, it tends to be Dandelion or Rocket or whatever, but I don't think it's specified by the greek ya-yas, its whatever is to hand.
I think cabbage is a universal in climates with a real winter: its hardy, it grows into the colder months if you let it, its viable for pickling and salting, and flatulance aside is great nourishment. Shame that kids hate it, but eh, the ones which survive fatten up fast on it, so there's protein latent in cabbage if you need it.
Cabbage in school meals in the 60s was indeed served in an ice-cream scoop puddle next to the mince and tatties (or haggis, being scotland)