A family resemblance

A giant ragweed stalk with a sunflower behind it; click for greater detail.

Now that you’ve gotten a close look at the tiny flowers of giant ragweed, Ambrosia trifida, the only thing you might think they have in common with a sunflower is the bit of yellow at the lower end of each “bell.” Yet botanists have placed ragweeds in the same family as sunflowers, the huge composite family known technically as the Asteraceae, which includes asters, daisies, thistles, and a lot more. Although the wind-pollinated flowers of giant ragweed and the insect-pollinated flowers of the familiar sunflower (one of which you see here out of focus in the background) are so unlike, the plants themselves have some similar features: both often grow taller than a person, and both are stocky and coarse and covered with rough hairs. Look at the giant ragweed stalk in today’s photograph, taken back on June 22, and compare it to the stalks of mature sunflower plants you’ve seen, or to the one shown in this column on June 23. Look also at the young ragweed leaf in the upper right of today’s picture and compare it to the young sunflower leaves featured in the first days of this blog. Welcome to the family.

I made this photograph, like a number of the others that have appeared in this blog, in Austin on the lot on the east side of US 183 south of Braker Lane that’s adjacent to Costco and Wendy’s. That property is in the midst of being redeveloped, so I don’t know how much longer I’ll be able to go photographing there.

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