1 lb. privet fruit (Ligustrum obtusifolium) simmered in 4 cups water and 2 tsp. salt. Unmordanted skeins simmered 1 hour without plant material, then added fruit back into dye bath. Let cool overnight: clear silvery grey with green tint.
This experimentation simply means that I'll have a hard time reproducing this color. I would like to find a book about natural dyeing that explains chemical reactions and offers recipes for less toxic mordants.
I am considering raising alumroot (Heuchera americana), a native wildflower. We found some growing among weeds where forest meets lawn at home. We have protected the plants with fence. Deer eat the flowers, so only the alumroot deep in a snarl of multiflora rose, honeysuckle, periwinkle, and greenbriar could survive.