Wild Foods- the perfect Freeganism

I received a delightful gift this weekend from our new friend Amos. He was outside playing with my children and approached me with a handful of greens as a wild contribution to lunch. I had no idea that all around my house was a tart green loaded with Vitamin C called Sheep Sorrel. I quickly browsed one of my wild foods books, but it wasn't in it. It's actually regarded as a noxious weed, but I think it makes the perfect addition to my daily cheese sandwich on rye bread! Well this lovely sorrel has both culinary and medicinal uses. So my research is, as soon as possible because all it takes is one frost and it's gone, how I can save it for the winter!