Growing up--we kids were often sent to the meadows to pick Sorrel for soup.
My sister, who lives in Alaska, grows it in her garden just for that purpose. It is almost like Spinach Soup--but has a definite sour taste. I only remember that it was seved with chopped, boiled egg in it--and, probably, a dollop of Sour Cream. We ate ALL soups with Sour Cream mixed in it. Have no idea what else went into that soup--but it was pretty good.
I also remember that there were 2 kinds of Sorrel. The one you describe, Sharon, sounds more like the one we used to call "Horse Sorrel". This one was not used in cooking...It was rough and had those stalks with reddish-brown blooms...
The culinary Sorrel is extremely high in Vit. C and other good stuff.
Sorrel was used in "the old country" to make borscht; we used to buy it in jars in the store when I was young. We always ate it with sour cream. My mother used to make a similar Spinach Borscht, also served with sour cream.
Gita - It was my grandparents who came from "the old country", which was Russia before it was the USSR, around the turn of the (previous) century. And, actually, my paternal grandparents came from what is now Ukraine.
Sharran - the sorrel soup that was in the jars was called "Schav", which is a Yiddish name for the soup. I liked my mother's spinach borscht better.