Back in the summer of 2008 when I was first ordering plants for our winter garden, I came across an item called "tyfon" or "Holland greens." It was in the section of the Territorial Seed catalog devoted to cover crops, and indeed when the seed packet arrived it said "EDIBLE GREEN MANURE." How appetizing! But in farming lingo, a "green manure" is just a cover crop that improves the soil... multiple sources said that tyfon could be eaten by people as well as animals, so I ordered it, along with several other crops that Territorial promised were winter-hardy.