The following material is from a letter I received from Jean Auel in relation to the foods mentioned in The Clan of the Cave Bear
In Traditional Plant Foods of Canadian Indigenous Peoples by Kuhnlein and Turner, under Common Milkweed (Asclepias syriaca), they state, "The young shoots, stems, flower buds, immature fruits, and even the roots were boiled and eaten as a vegetable by various Indigenous groups of eastern North America, including the Iroquois, Ojibwa, Micmac, Potawatomi, and various Plains peoples..." They go on to describe the way the various peoples used the different parts of the plant, and finish with, "This milkweed is delicious as a green vegetable and should be investigated for domestication."
Under a reference for "Sweet coltsfoot (Petasites frigidus)" they say, "Young leaves eaten mixed with other greens, and leaves used to cover stored food, and ashes mixed with chewing tobacco as flavoring by some Alaskan and Siberian tribes." Under "Common coltsfoot (P. palmatus)" they say, "In Washington, the Muckleshoot ate the boiled stems, and the Makah and Quinault used the leaves to cover berries and pit-cooked food..."
There are many references for the lily family, including wild onions, mariposa lilies and various others. I have personally eaten roots and buds of day lilies (the buds have the texture of green beans, but they taste like day lilies), as well as different parts of cattails (sometimes referred to as the "supermarket food of the wild" because so much of it can be eaten or used for other purposes), and thistles, (it's best to strip the sharp spines off before it's cut, by holding the top and shaving the stems with a knife.) Thistle stems have the texture of celery, but they taste like artichokes (same family), and they turn dark fast, so they need to be cooked, or at least par-boiled quickly.