2 cups red cabbage (Brassica oleracea - along with kale, collards, cauliflower, broccoli...) simmered in 4 cups water and 3 T vinegar. Did not work.
3 ounces curly dock (Rumex crispus) boiled in 6 cups water in cast iron kettle. Skeins simmered 1 hour with plant material. Let cool overnight: medium grey with green tint.
2 cups white oak inner bark (Quercus alba) simmered 1 hour. Sieve. Skeins simmered 1 hour. Did not work. Though the dye bath was a rich auburn tone, I believe the tree had been fallen too long and the tannins leached.