some plants to make ink out of:

Madder    dig pencil thick roots anytime,

Weld, July
Dyers Knotweed (at Gaining Ground?)
Japanese Knotweed?Stinging Nettle
Shaggy Ink Cap mushrooms
Pokeberry
Oak Galls
Acorns
Woad, after the leaves reach about six inches in length, June or July
Iris
Goldenrod, late summer
Walnut
buckthorn berries

lots of good stuff on native american dye sources here
lichens,

more dye plants
Sumac berries and leaves (blueblack)