Ragweed Medicine. Ambrosia trifida. One of those plants people love to hate, and I love to use! Generally, I harvest the leaves before they go to flower and make a fresh plant tincture out of them. Believe it or not, the tincture is wonderful for opening up the sinuses and tightness in the chest. I have actually traded this plant for other medicinal plants across country to herbalists who dont have it prevalent in their bioregion. More on it in my book!