​Bur Ragweed, Annual Bursage, Flatspine Bur Ragweed,Ambrosia acanthicarpa,Sunflower Family (Asteraceae)

Found in dry waste areas, roadsides
Seen blooming in September at Los Alamos Airport

Anyone suffering with a runny nose, itchy eyes and sneezes should know that Ragweed could be the cause, not COVID-19. Ragweed pollen is considered the number one cause of hay fever in the late-summer and fall. Each plant can produce over a billion grains of pollen per season which occurs from mid-August until frost. This Ragweed is one of several species of Ragweed that grow in our area. It grows to 3 feet high, erect or sprawling, with deeply lobed hairy leaves. Although weedy in appearance, on closer inspection the flower structure is interesting. Male flowers hang from the top portion of the stem like little umbrellas with a dark stripe and can look yellowish due to the color of the pollen-laden stamens. Female flower heads below are spiny burr-like structures in the leaf axils. The fruits are very spiny and painful to touch. Native Americans used an infusion of the plant for menstrual obstructions, and the ground root was placed in the tooth for toothache. The ash of the leaves was used in ceremonies. The scientific name, ambrosia, is Greek for food of the gods, while acanthicarpa means having thorny fruits, hardly food for the gods. Source.  
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If you are trying to identify a different flower then you can check what other flowers bloom this month. If you cannot identify a flower from the website, send a photo and where you took it to [email protected]. Read online for tips.