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. Check out our links page for some suggestions.
Our marigolds are grown in 7' diameter raised garden bins. They have not been treated with pesticides and were fertilized with llama poo from our llamas.
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.