Marigold flowers are a great natural dye. They produce yellows to greenish-yellows to golds depending on the mordant used. We do not sell the mordants but they are available online from several retailers.
Our marigolds are grown in raised beds in the back yard. They have not been treated with pesticides. We have lost our access to llama poo since we moved into town so have switched to environmentally friendly organic fertilizer.
Each 4 ounce bag of dried flowers should give you nice color on 4 ounces of protein fibers such as wool, mohair and silk. You can stretch the dye bath to more fiber than 4 ounces but will get softer lighter shades.