Giant ragweed when it’s scraggly

Giant ragweed; click for greater detail.

In contrast to yesterday’s picture, giant ragweed can sometimes look less linear and more scraggly, especially at the top, as seen here on another plant growing at the same site as the one in the previous post.

For more information about Ambrosia trifida, including a clickable map showing the great many places in North America where the plant thrives, you may follow the siren’s song to the USDA website.

© 2011 Steven Schwartzman

Giant ragweed

Giant ragweed; click to enlarge.

People with respiratory allergies have at least one reason to dread the coming of autumn, for that’s when ragweed chooses to flower. Its flowers are small and inconspicuous, but these plants don’t rely on insects to spread their pollen. Instead, they release their pollen into the air in the expectation that it will be blown to other receptive plants of the same species. Because that’s literally a hit-and-miss proposition—with much more miss than hit—ragweed releases large amounts of pollen, so that even if the hits amount to only a small percent, a small percent of a large number is still a success. Unfortunately a portion of all the misses ends up in our noses and causes us plenty of suffering. (I say us because I’m susceptible.)

While other species of ragweed stay relatively close to the ground, in central Texas we have one, Ambrosia trifida, that justifies its common name of giant ragweed. This plant grows erect and can reach heights of 10 ft (3 m). Not only that, but it can form large colonies that line roadsides and fill fields. I found a lot of it (in both senses of lot) beginning to flower on September 9 on the same property where I photographed some peppervine flowers and buds earlier in the summer. This is the lot on the east side of US 183, a block south of Braker Lane, adjacent to Costco and Wendy’s, that’s about to be redeveloped, so I went back to see what else I could photograph before it’s too late.

This giant ragweed plant’s central stalk is vertical, but it has many branches that give the overall effect of a candelabra. You’re seeing only the upper portion of the plant here; note the angle at which I had to look up to include the top of the plant, an indication that it was a few feet taller than I am.

For more information about Ambrosia trifida, including a clickable map showing the great many places in North America where the plant grows, you can visit the USDA website.

© 2011 Steven Schwartzman