Common ragweed is a native annual forb famous for its production of highly allergenic wind-born pollen.

As a summer annual, it readily infests summer crops such as corn and soybeans if not treated. It is not as prevalent in Oregon today due to better crop and right-of-way herbicides though it still can be found in late summer in non-crop areas.

Ragweed is a very common invasive annual. It germinates early in the spring and reaches the flowering stage towards the middle of July, at which point it begins to release pollen. It is the leading cause of seasonal allergies in Quebec.
Rip it out or cut it down to ground level before the end of July.