For folks that love to knit, crochet or use yarn in other ways you might like this tutorial for growing your own indigo and then dyeing skeins of merino wool. It is really neat to see the wool go into the water and vinegar that looks super green from having had the chopped up indigo soaking in it. Then when they took the wool out it looked really green but as the air hits it the dye oxidizes and turns a glorious blue color. The more it dries the bluer it gets. If you are interested in dyeing your own yarns you can keep scrolling past the article on indigo and you will find how she uses woods, beans, and even bugs to create beautiful colors with which to dye the yarns.
Whether you want to dye your own yarn to use the yarn for your own creations or add them to yarn that you will sell there is a lot of good info to be found on Dirt Under My Nails. I thought the indigo article was very interesting. I remember reading a novel one time that took place back in the very olden days when they made indigo dye and would dye bolts and bolts of denim with it. For any one that works with yarn this is a great skill to learn. Growing your own indigo would make you feel even more accomplished I would think.