a natural dye
People who use plants to dye fibers already know about this dye, but my personal discovery of it came about in washing my jeans. Cliff hanger: the dye plant is named at the end of a pretty boring story.
After wearing my jeans for several days I noticed they were in need of a wash. I wash them by hand, so I get to see intimately what washes out of them. I first plunged them in cold water to pull out the mineral (soil) element of the dirt and to wash out some of the green stains without setting the protein in hot water. At first I noticed a red tinge in the water and was wondering whether it was from that loess soil I'm newly working with. The more I plunged, the more the water looked like cherry Kool-aid, so the color could not be from the soil. Quite weird.
When I switched to plunging the jeans in hot water with detergent, there was still red coming out of them, but now so was the blue from the denim, so my water was like dilute grape Kool-aid.
Two clear water rinses later and the red was pretty much gone. Thinking back over what plants I'd handled, I suspected the bedstraw (Galium) I'd weeded the previous day. Sure enough, the internet agrees with me. Bedstraw yields a red dye. How in all these years of weeding bedstraw did I never notice this?
Keep your eyes open. There are amusing and useful things to observe.