Did you know that there are TWO different ragweed plants? I found a giant ragweed plant (Ambrosia trifida var. trifida) this year. It happened to be growing right next to common or annual ragweed (Ambrosia artemisiifolia).
Giant ragweed can grow up to 12 feet tall. The oval leaves are 3-12 inches long. And in case you were wondering, yes, giant ragweed will cause allergies just as much as common ragweed.