Goldenrod – Pretty Flower or Evil Invader?

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.