|Photo by Marty Horowitz 3/15/2017|
Yes, Canyon Ragweed (Ambrosia ambrosioides) is in bloom! Note lots of yellow dots on the male flowers. Lots. That's the pollen. Plants produce much more pollen than is actually necessary to join with the eggs (ovules, in plants; but let's not get bogged down in terminology). And pollen is generally what people are allergic to. This plant is no exception!
Note the lime-green burr-like flowers below the mini-sunflower-like male flowers. Those are the female flowers. Far fewer in number. And, of course, they don't produce pollen.
More photos here and at the link above.