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Goldenrod, Allergies, and Spitballs.

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Every year at this time, I find myself defending goldenrod from unfair attacks by sneezy, watery-eyed, congested people looking for something to blame for their discomfort.

Poor goldenrod; for a showy native wildflower (actually numerous species of wildflower), it sure has public relations issues.  Some species, particularly Canada goldenrod, tend to act pretty weedy – showing up quickly and abundantly in abandoned cropfields and chronically overgrazed pastures.  In some cases, it can look much like an invasive plant, causing some (including me) to wonder about whether it warrants some control efforts.

Canada goldenrod (Solidago canadensis). A very pretty flower with a spotty reputation.

Canada goldenrod (Solidago canadensis). A very pretty flower with a checkered reputation.

But it’s during allergy season that goldenrod’s reputation takes the biggest hit.  When people start to sneeze and wheeze in the late summer/early fall, they look around (through their red puffy eyes) for the culprit, and goldenrod is the tallest, showiest, weediest looking plant they see.  Ah ha!  That must be the problem plant!

Well, actually…

Allergic reactions to pollen are usually the result of breathing air that contains pollen grains.  Our bodies react to the chemicals in those pollen grains, causing symptoms that include sneezing, itchy and watery eyes, congestion, and others.  The pollen we breathe in comes from plant species that rely on the wind to transport their lightweight pollen from flower to flower.  Those wind-pollinated species make a tremendous amount of pollen to increase the chance that at least some of their pollen grains will get blown toward other plants of the same species.

Grasses, including indiangrass (Sorghastrum nutans) don't have showy flowers because they don't need to attract insects to carry their pollen. The wind does the job instead.

Grasses, including indiangrass (Sorghastrum nutans) don’t have showy flowers because they don’t need to attract insects to carry their pollen. The wind does the job instead.

In contrast to wind-pollinated plants, plants that are insect pollinated tend to create heavier, stickier, pollen grains that don’t get picked up by the wind.  Instead, those plants rely on bees and other insects to carry pollen from flower to flower.  To attract pollinators, insect-pollinated plants have to create big, showy, and colorful flowers.  Wind-pollinated plants such as grasses, pine trees, and ragweed don’t need to spend resources making big fancy flowers.  They just make lots of pollen and let it blow.

Now, consider goldenrod flowers.  Definitely showy and colorful, right?  That, and the numerous insects crawling around on the flowers make it pretty obvious that goldenrod is insect pollinated.  When you walk through a patch of blooming goldenrod, you’ll never see a big poof of pollen come off the flowers as you knock into them.  Instead the pollen sits tightly on the numerous little flowers, waiting to stick to a fuzzy bee or other insect.

A bumblebee gathering pollen from stiff goldenrod (Solidago rigidus) in a restored prairie near Sutton, Nebraska.

A bumblebee gathering pollen from stiff goldenrod (Solidago rigidus) in a restored prairie near Sutton, Nebraska.

When you look at the evidence, it seems obvious that goldenrod isn’t to blame for our itchy watery eyes and congested noses.  How, then, did it become such a hayfever scapegoat?

I think of goldenrod as the kid in class who’s generally a good student, but always dresses a little too flashy and laughs a little too loud.  Ragweed, on the other hand, is like the plain-dressed quiet kid who throws spitballs at the teacher when her back is turned.  When the teacher whips around to see who’s responsible for the spitball in her hair, who do you think she’s going to blame?  The loud kid who’s laughing uproariously, or the quiet kid pretending to read his lesson?

Exactly.

Poor goldenrod…

Western ragweed (Ambrosia psilostachya) has tiny non-descript flowers, but produces LOTS of pollen, which is released into the wind for transport.

Western ragweed (Ambrosia psilostachya) has tiny non-descript flowers, but produces LOTS of pollen, which is released into the wind for transport.  Ragweed species are a major contibutor to seasonal allergy attacks.

Well, now that you are in the know, maybe you can help me restore the good name of this much-slandered native plant.  Just think of the popularity you’ll gain when you walk up to your puffy-eyed friends and explain to them (between their sneezing attacks) the ecology of wind and insect-pollinated plants!  To really drive the point home, maybe you should grab a bouquet of goldenrod flowers and shake them in your friend’s face to prove that no pollen comes out.

Just be sure to check for bees first.

Goldenrod – Pretty Flower or Evil Invader?

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When did goldenrod become such a bad plant?  It’s really quite attractive, I think.  It’s a signature plant of the late summer/early fall prairie.  Yes, some species can form fairly dense patches and can take advantage of a weakened grass stand to get a quick foothold.  But would we complain if compass plant did the same thing?

Canada goldenrod and big bluestem at Griffith Prairie (a preserve of Prairie Plains Resource Institute).

Some people mistakenly blame goldenrods for hay fever. That, at least, is an easy illusion to dispel.  The bright colorful flowers and the abundance of pollinating insects crawling all over them clearly indicate that goldenrods are insect pollinated, not wind pollinated like ragweeds and other hay fever-causing species.  So spread the word… goldenrod doesn’t make you sneeze.

Apart from the hay fever myth, though, there are some prairie ecologists who are struggling with how to categorize and treat goldenrod in a prairie plant community.  There are, of course, many species of goldenrod – including some very rare prairie and savanna species.  Most people are fine with categorizing those as species in need of conservation.  I’m talking about some of the taller and more prolific/common species like Canada goldenrod and stiff goldenrod.  Even Missouri goldenrod (which, ironically, is the state flower of Nebraska) gets occasionally thrown into the “down with goldenrod” conversation.

One issue with these goldenrods is that they are very effective colonizers.  Their windblown seeds can disperse widely and can quickly establish in bare soil and/or in places where competition from other plants is light.  And, unlike many other colonizers (ragweeds, hoary vervain, black-eyed susans, and many annual plants) goldenrods don’t typically fade away in the face of competition from perennial grasses.  These characteristics make them a staple plant of old fields – cropfields that are allowed to stand idle and be colonized by whatever species can do so.  That’s an ideal situation for goldenrods, and they can quickly become one of the dominant species in an old field.  Many prairie restoration (reconstruction) projects that attempt to convert those old fields to prairie vegetation have found that simply tilling those old fields and seeding into them doesn’t work well because of overwhelming competition from goldenrods and other old field species that have built up populations and seed banks.  However, that’s not a knock on goldenrod, it’s a failure to properly prepare the seed bed for the restoration project.  When seeding into a site that’s been repeatedly cropped and doesn’t have a history of goldenrod populations, goldenrod is usually much less of an issue.

The colonizing ability of goldenrods gets them in bad with ranchers as well because if cattle grazing continually weakens the dominant grasses in a pasture, space opens up for the establishment of other plants.  Species like goldenrod that are not very palatable to cattle do particularly well in those circumstances.  And, again, once they establish, their ability to survive even when the grass regains its vigor sets them apart from other species like hoary vervain and ragweed, which tend to fade quickly.  Once they’re abundant they look like some kind of noxious weed, and it’s not uncommon for prairies to be sprayed to control goldenrod – a native wildflower.

So, which is it?  Are these goldenrods showy wildflowers that provide valuable resources to pollinators in the fall?  Or are they plants gone bad and in need of suppression?  Maybe both – depending upon the situation.  What I’ve seen in Nebraska prairies is that these goldenrods can look very abundant when they’re blooming, but the prairie community around them maintains its diversity pretty well, and the goldenrod tends to plateau at a certain density and not get to the point where it forms large monocultures.  But I’ve seen restored prairies in places like Illinois where it sure looks like goldenrod is dominating the plant community to the detriment of other species.

Goldenrod... pretty fall flower or aggressive invader of prairies?

If goldenrod needs control in some situations, what’s the best technique?  It doesn’t seem to be suppressed by dormant season fire.  Broadcast herbicide spraying is almost certain to be counterproductive both because it destroys the much of the larger plant community and because goldenrod will almost certainly benefit more than other species from that suppression of competing plants.  The fact that goldenrod is not palatable to cattle might mean that it’s susceptible to repeated defoliation (mowing, etc.) or prescribed fire during the growing season.  Has anyone had luck with that?

I’d like to hear about examples of goldenrod gone bad, successful or failed attempts to suppress it, or passionate defenses of these pretty flowers…  Just leave a comment below.