Ever Get Tired of Ragging on Ragweed?

“Naturam expellas furca, tamen usque revenit.”(“You can drive nature out with a pitchfork; she will nevertheless come back.”)--Horace

At any given time, roughly 25% of the population is suffering from allergic rhinitis, known more commonly by the inaccurate name “hay fever”.  There are, of course, some people who are allergic to hay, but since they are typically smart enough not to go on hayrides, or venture too close to a horse barn, they generally don’t have much of a problem.  And yet… there’s that nasty fact that airborne pollen from a whole host of non-hay sources gets under their skin (or, at least, into their

nostrils).

Roughly half of all reported cases are the result of sensitivity to one particular culprit – ragweed.  It is difficult to know, of course, how many cases there are which go unreported simply because, while irritating, the symptoms were not bad enough to lead to a doctor’s visit.  That having been said… Ragweed season is an early Autumn affair in the Brazos Valley, and… yeah, it’s here.

We say “ragweed”… but this is actually not just one species, it is an entire category of plants, some of which are even grown on purpose, believe it or not.  Still, the two most commonly cited varieties are most definitely wild and unwelcome in the typical garden (though we know of some atypical gardeners who swear by them!) – common ragweed (Ambrosia artemisiifolia) and great ragweed (Ambrosia trifida).  There are around 50 species in total, found all over the Americas (and now running rampant as invasive species in Europe), and many of them are quite attractive, aside from the fact that they make so many people miserable.

Hay fever was first identified in 1819 by physician John Bostock; pollen was identified as the causal agent in 1859 by Charles Blackley; it was not until 1906 that Clemens von Pirquet identified the hypersensitivity of the human immune system as the mechanism by which the condition creates such misery.

All the years since then, of course, have seen the most typical of human reactions – burn the offending plants!  Kill them all!  And, sure enough, since the identification of the various ambrosia species known as “ragweed” there have been an almost uncountable number of strategies attempted to eradicate the offending weeds.  Each has met with very limited success.  Some have only made things worse.

Pulling the plants up by hand, of course, presents a high degree of difficulty.  For one thing, they must be identified very young, before their tough root system grows sufficiently to tax one’s muscles mere minutes into what (by nature) must be a long day’s work.  To make matters worse, while the pollen is not toxic (remember, it’s your own immune system that generates the histimines in your system that are making you ill), the leaves and stocks of the plant are mildly toxic, enough to irritate your skin and, after enough exposure, give you a nasty rash.

Mowing is somewhat more effective, provided it is done once the plants are tall enough to cut, but still young enough not to have bloomed.  And, of course, it must be repeated frequently.  And… it only gets those plants growing in a lawn or field… any plants growing in a garden plot or on a farmstead, or in an out of the way ditch, culvert, wild space, vacant lot, etc. will be untouched.  And, since the pollen can stay in the air for days or even weeks at a time, and can be borne hundreds or sometimes even thousands of miles… mowing down your own ragweed does you no good whatsoever if you are downwind from someone else’s.

Not too many years ago, a commonly applied “solution” was to burn fields with ragweed; we’ll leave to your imagination the sum total of what exactly was wrong with this little stratagem.  Among other things, ambrosia smoke is its own form of toxin, irritating in ways the pollen could only dream of being.  Fortunately, this strategy is no longer recommended even by the most backwards of agricultural extension agents.

And then there is the chemical approach.  Vast quantities of herbicide have been applied to ragweed patches over the years.  The problem, of course, is that ambrosia is particularly resistant to the vast majority of commercially available herbicides; pour buckets of Round Up on it, and it will thank you for the watering and go on its merry way.  Even through our sneezes, we can admire its tenacity.

Worse than the fact that herbicides don’t work, however, is that herbicides do kill the one thing that does work.  Ragweed populations can only be kept in check using natural means.  And there are, it turns out, plenty of animals who not only are not irritated by these plants, they thrive on them.  There is a long laundry list of Lepidoptera species which thrive on ragweed.  That’d be moths and butterflies, species who, while they like eating ragweed, do not like ingesting herbicides.  Oops.

A 1973 review of ragweed control techniques published in the Bulletin of the Torrey Botanical Club found that regardless of which control technique was used, after a few years there was no appreciable difference from simply leaving the ragweeds in place.  We could not find any more recent efficacy studies, but we suspect that given the increase in environmental degradation, fields with herbicidal controls are probably worse than simply leaving the plants in place, owing primarily to the decimation of foraging populations.

Proper population control of any “weed” (basically, any plant you find noxious for whatever reason) cannot take the form of eradication.  The sooner we rid ourselves of the notion that we can “do away with” things we don’t like in nature, the better.

No, “control” can only come in the form of management.  And management means creating balance.

We already noted one part of this equation, tending to the foraging populations, namely moths and butterflies.  Helping those populations along by planting other food sources is one important step in limiting the wild stands of ragweed – plant enough milkweed in your garden, and not only will it take up space that might otherwise be used by a resourceful a. artemisiifolia plant, but it will succor enough flying critters to eat any nearby a. artemisiifolia plants that might have otherwise given you trouble.  Plants in your neighbors yard, for example, which you would not have been able to get at with a mower, a blowtorch, or a spray bottle full of poisons.

And we just hinted at another solution – increased biodiversity in your garden, making use of every available space to plant other things.  One of the biggest problems with lawns (and we have written before about how icky we find them) is that they limit biodiversity and create niches for invasive “weed” species.  We hate the term “weed” but in this case, its meaning is appropriate – a “weed” is a plant whose presence is indicative of a problem.  Note that the “weed” is not the problem, it is there because of the problem.

By increasing biodiversity (putting in a flower, herb, veggie, etc. bed, preferably a combination of all of the above) the niche for the offending plant is eliminated.  There m

ay still be room for the odd individual or two… but there is no longer room for a large stand of invasives, and there will be a much greater population of foraging insects and other creatures who, after having sampled one species, moves on to another.

Ragweed sensitivity in the general population is higher now than it has been in hundreds of years; there are a lot of reasons for that, all of them related to human activity.  Various forms of pollution have left our immune systems primed for hypersensitivity to pollen; additionally, once pollen sensitivity has been kicked off, all those chemical pollutants in the air are more keenly felt in our nasal passages, lungs, eyes, skin… it’s enough to make you sick.

But it’s not the ragweed’s fault.  It is the fault of the lack of balance in our relationship with nature.  We won’t begin to truly breathe easy until we give up on our stubborn attempt to tell Mother Nature what it is we want her to be doing.  Mother Nature knows exactly what she needs to be doing – in the meantime, try some lemon and local honey in hot water; ragweed won’t be in bloom forever, and a nice hot beverage is as good a way as any to while away the time until the elm trees are in bloom…

Happy farming!