Ragweed is a plant that people love to hate.
Both common ragweed, Ambrosia artemisiifolia, and giant ragweed, Ambrosia trifida, are common pests in the eastern and central parts of North America. They are the cause of about 90 percent of the allergies caused by pollen during late summer and fall in the United States, and many other plants and flowers get the blame.
Even though they are pests to most of us, they also were and still are in medicine. The Native Americans used these plants to treat several different ailments. They rubbed crushed green leaves on small cuts to stop bleeding and on insect bites, bee stings, and on hives to stop itching and heal wounds. A leaf tea was used to treat fevers, nausea, dysentery, and nosebleeds. Some Native Americans treated strokes with a root tea made from common ragweed.
Both common and giant ragweed is collected commercially and used in medicine to treat hay fever caused by ragweed. Goldenrod is often thought to be the cause of hay fever but is seldom the culprit. Its pollen is too heavy to be carried by wind and few people, who are allergic to it, will be in field of ragweed. Ragweed will not only cause you problems with its pollen but you may also have an allergic reaction if you touch or eat it.
Both plants are annuals and have similar blossoms, but those are the only resemblances. Common ragweed grows 1 to 5 feet tall and giant ragweed grows 6 to 15 feet tall. They can be found in bloom from July through October in waste places throughout eastern and central America.