Eliza Lucas Pinckney & Indigo Dyeing yarn naturally with grapes. Could be an interesting art/science activity to do with kids. Could also touch on aspects of history - taking about how people used to make and dye their own clothes and fabrics.
The class I took from Al-Jania at Gulf Wars 2014 included pokeberry. I got to bring home a half gallon jar of dye bath from the class. :) [ Pokeberry Dye Inspiration: from Harvesting Color by Rebecca Burgess ]