Which genus includes the plant commonly known as ragweed?

The plant commonly known as ragweed is classified under the genus Ambrosia. This genus is well-known for several species that are significant contributors to seasonal allergies due to their production of pollen. Ambrosia plants are typically found in North America and are characterized by their small flower clusters and distinctive lobed leaves. They often thrive in disturbed soils and open areas, which can facilitate their spread.

In contrast, the other genera listed do not include ragweed. Xanthium refers to plants like cocklebur, which have different flowers and uses. Helianthus includes sunflowers, known for their large, showy blooms and distinct aesthetics. Rudbeckia encompasses coneflowers or black-eyed Susans, which are popular garden plants recognized for their bright yellow petals and dark centers. Each of these genera has distinct morphological and ecological traits that differentiate them from Ambrosia.