Achoo, Sniffle, Ragweed

11 Jul


Ambrosia artemisiifolia


Isn’t “ambrosia” food of the gods, incarnate here on earth as that marshmallow-coconut-jello salad?  What was Linnaeus thinking when he named Ragweed that!?

[On the off-topic of Linnaeus as a naming nut, it amuses me that in the native-plants-in-the-landscape classic, “Going Native,” Richard Workman questioned Linnaeus’s handle “cynophallophora” (dog-you-know-what-bearing) for Jamaican Caper.  “Considering all the beautiful and attractive characteristics of this plant, I can’t help wondering a little about Linnaeus and his motivation.”  That’s wimpy by Linnaean standards.  That D.O.M. was not fit for polite society.]

Ragweed in Cypress Creek (by JB)

It’s not exactly divine, but Ragweed is a native weed distributed, get this (!) from Alaska to Florida, and from there globally as an invasive exotic.  It loves disturbance.  Have you ever seen how Ragweed monopolizes freshly excavated dirt?  Among other adaptations, the seeds (achenes) are tiny burrs no doubt carried by anything that moves.  And more interestingly, the seeds accumulate in the soil with varied germination times.  Some sprout lickety-split, others slumber for decades, just waiting for that road grader.  John and George this week hiked the Cypress Creek Natural Area near Jupiter Farms and, after passing by all the pretty photogenic wildflowers, focused on the dominant species.  The spoil banks along the graded road are  ribbons of Ragweed.

In a fun little book, “My Weeds,” garden writer Sara Stein described a classroom activity called “Magic Dirt” where the children go outside and fill a flowerpot with nice “clean” soil, and place their pot on the classroom windowsill to witness awakening weeds.  I LIKE it!  The Cypress Creek road banks are Magic Dirt on a macro-scale.  Food of the gods for a mile.   How long have some of those seeds been banked in the soil?   Perhaps their parents caused sneezing at the Battle of the Loxahatchee on more or less the same ground in 1838.

Ragweed babies aplenty (by JB)

That’s the thing we all know about Ragweed, Gesundheit!  The plant releases pollen like a fiend.  Let’s linger on that a moment, because wanton wind pollination is unusual in the mostly straight-laced insect-pollinated Aster Family.

Have you ever know a human family where one generation builds up a tightly run business, only to have a sloppy subsequent generation let it all go to seed?  (This occurred with a vengeance, perhaps literally, in my own family.)  Ragweed is the hippie cousin.  Most members of the Aster Family have elaborate little flowers with a hyper-specialized pollen-presentation system where first the style pushes a tiny dollop of pollen out of a tube formed by the anthers, and then the style delicately rises and becomes pollen-receptive, all very precise,  proper, and timed.  In “good” members of the Aster Family those  tiny flowers cluster cooperatively into those showy false-flowers of Asters, Chrysanthemums, Dahlias, Daisies, and  Sunflowers.    So organized, so controlled.

Photo by JB

Ragweed says bah!  Ragweed shuns showy flower heads.  It spurns elaborate pollen presentation.  It repudiates insect pollinators, nectar, and perfumed scents.  It scorned Brooks Brothers,  put on torn bluejeans,  and chose a different path:  wind pollination.  It thinks it is a grass.

The small Ragweed flower heads look like single flowers, and are arranged in catkins (linear clusters), as in many wind-pollinated plants.  The pollen-producing (“male”) flowers are separate from the seed-making (“female”) flowers on the same plant.  (Yes, self-pollination can occur on one plant; that way, a single seed can pioneer a whole new population.)

Male flower heads (by JB)

The female flowers are little more than an ovary with two big stigmas jutting out like antennae to catch wind-borne pollen. The male flowers are nothing more than pollen bags.

And that is why Ragweed is so sneezy… it lives to pollute the air.  I’ve read that one plant can generate a billion grains.  Who’s counting?

And why is air-borne pollen so allergenic?  Did you ever wonder how a flower knows which pollen to let fertilize its seeds, and which to thwart?  I mean, a female cat knows a male cat, and a female turtle probably knows a male turtle.  But flowers are different.  The stigma (pollen-receptive surface) has built-in pollen recognition ability.  A pollen grain landing on a stigma can release proteins  that ask the stigma, “am I on the right stigma”?  The stigma can then allow the pollen to perform its function, or kill it.  As I suppose speculatively,  when pollen catches in our moist sinuses, it releases its recognition proteins (and it has plenty of additional  proteins) and asks, “am I on a stigma?”   Our immune system recognizes that foreign protein as an antigen.

Linnaeus (stolen from the Internet)


Posted by on July 11, 2012 in Ragweed


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5 responses to “Achoo, Sniffle, Ragweed

  1. Mary Hart

    July 12, 2012 at 3:47 am

    In UK ragwort is the common name for Senecio jacobaea, it is a poisonous if striking plant w. bright yellow flowers,and is potentially lethal to horses, so must be reported and eradicated. On the subject of Linnaeus – those old botanists werenot always worried about polite society – what about Phallus impudicus for the common stink horn fungus …

    • George Rogers

      July 12, 2012 at 8:27 am

      Thanks Mary, I did not know that and am glad to. Especially because I have sort of an odd little interest in Senecio species as examples of weeds that can sneak in multiple generations per year. Now I must look up S. jacobaea. There was a stinkhorn in hte mulch in front of our house not long ago…the only thing more impolite than its appearance was the smell. Holy Smokes. I found it not by seeing it, but by coming out the door and getting mugged by the stink.

  2. Steve

    August 16, 2012 at 9:39 am

    My favorite naughty name is Clitoria fragrans, I’d love to read a blog about the etymology of that one.

    • George Rogers

      August 16, 2012 at 12:55 pm

      Steve, What is my elderly aunt checks the blog!? At age 60 I’ve learned from many bad experiences to attempt to behave sometimes.

  3. Steve

    August 18, 2012 at 8:37 am

    Science knows no barriers…


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