Western ragweed is a type of plant that is known for causing hay fever and respiratory allergies. This plant is also commonly referred to as Ambrosia psilostachya or common ragweed. However, there are also several other synonyms that are used to describe this species of ragweed such as naked-seeded ragweed, pinnate-leaved ragweed, and western ragweed. These alternate names may be used in different regions or by different researchers, but they all refer to the same plant. Western ragweed can be found throughout North America and is often considered a weed due to its ability to spread rapidly and compete with other, more desirable plants.