Anyone who can make a pot of tea can dye a skein of wool or yard of plain linen to whatever color they want, using commonly found plants.
The Social and Ecological Impact of Naturally Dyed Clothing
NATURAL DYE SERIES POST 1: SCOURING — Farm & Folk
How To Make Natural Dyes From Plants
Natural Dyes for Fabric: Natural Ways to Dye Fabric in Many Colors
Your Five-Step DIY Guide To Natural Dyeing - The Good Trade
Indigo Powder Grown in Canada - Vibrant Acres
How to Create the Green Yarn from Christmas at Plum Creek
Natural Dyeing Resources for Modern Crafters
The importance of using a mordant in natural dyeing - La creative