In Defense of Nature

 

Garlic Mustard—Exposing a Trail of Lies, Hearsay, and Ignorance

Garlic Mustard is claimed to be allelopathic, meaning that it makes the soil inhospitable for native plants to grow nearby. This claim is undoubtedly based upon the fact that this species is often the only plant found growing in some otherwise-barren areas. But a picture is worth a thousand words when it comes to disproving mis- and dis-information. As clearly seen here and in many other photos I’ve taken, even the most-adored plants (in this case, Dutchman’s Breeches, Dicentra cucullaria) can grow and bloom(!) in the vicinity of Garlic Mustard.

ALL TEXT AND PHOTOS © Marlene A. Condon

NOTE: The term “nativist” employed in this article refers to an advocate for policies that support the protection of native plants by removal of “invasive” alien plants.

 

“Blue Ridge PRISM [Partnership for Regional Invasive Species Management] Inc began as a volunteer-driven organization dedicated to reducing the negative impact of invasive plants in the northern Blue Ridge Mountains of Virginia. Effective invasive plant control is a community and neighborhood issue because these aggressive plants know no boundaries – flowing water, birds, hikers, vehicles, and animals [sic] scat all help to spread their seeds.”

 

https://blueridgeprism.org/about/

 

I don’t see how anyone could write that supposedly invasive plants are “aggressive” when it’s immediately stated that they are being spread by other entities. The statement is nonsensical and perfectly epitomizes the entire “invasive-plant” narrative: Blame plants for simply responding to environmental conditions. Nativists don’t recognize that by their own articulation of the “problem”, they expose the fatal flaws in their thought processes: a lack of perception and reasoning ability.    

 

Consequently, this organization commonly promotes misinformation that often employs an unhealthy dose of anthropomorphism. For example, the subtitle of a Blue Ridge PRISM "fact" sheet on Garlic Mustard (Alliaria petiolata) by Susan A Roth declares that Garlic Mustard is a “beastly invasive” that “[m]urders crops, [w]ildflowers, and [f]orests, [p]oisons the land” and “[k]ills butterflies”. 

 

https://blueridgeprism.org/wp-content/uploads/2021/09/Garlic-Mustard-Factsheet-2021-9-9-v1-FINAL.pdf)

 

The clear intention of Ms. Roth’s hyperbole is to make you believe you must rid your yard and neighborhood roadsides of this medicinal and culinary herb. But let’s look at the facts instead of PRISM factoids. 

 

The fourth sentence of this PRISM “fact” sheet states that, “By now, garlic mustard is destroying forests and killing butterflies in 34 states, ranging from the Northeast and Mid-Atlantic to the Midwest into the Pacific Northwest and Alaska.” This kind of overstatement is common in nativist attacks on so-called invasive plants, as is the fact that appropriate references are rarely provided to presumably support such exaggeration—as is the case with this web document. A lack of references should make the reader suspicious of the validity of such rhetoric, and with good reason, because it’s usually scaremongering based upon hearsay.

 

For example, the second paragraph tells us, “Within ten years of its arrival in an area, garlic mustard can take over the forest floor.” Really? I have just celebrated living in the same house for the past 37 years. My yard, in the shadow of the Blue Ridge Mountains, is surrounded by forest. Garlic Mustard grows in this area, but I can truthfully declare that it has made no attempt to “take over” the forest floor that surrounds me, and has only appeared in my yard twice—both times disappearing after setting seed.

 

Instead, Garlic Mustard has stuck to roadsides where the highway department distributes its seeds by sending out mowers in the fall (after the plants have gone to seed). Thus, Garlic Mustard’s spread can be directly attributed to people, as is typically the case with so-called invasive plants. And, if you don’t understand the true source of a problem, you are never going to be able to fix it (in this case, by mowing before Garlic Mustard has set seed).

 

In horticulture, the saying, “Right plant, right place” should tell everyone that plants grow only where environmental conditions are right for them. In other words, if conditions (amount of light, soil tilth, moisture) were conducive to native-plant growth in a particular area, those plants—rather than alien plants—would have come up and filled the area instead. Of course, it’s difficult for that to happen when the highway department keeps roadsides cut and the soil compacted, as well as polluting the soil with a salt slurry in winter. Let’s face reality here:  Human-maintained roadsides invite the toughest of nonnative plants to move in while discouraging less resilient native plants that can’t withstand such harsh growing conditions.

 

Yet, according to nativist postulation, garlic mustard should have “invaded” the forest floor and taken it over long ago in my area, which simply has not happened. Why? Because this plant needs a measure of sunlight and soil disturbance that you will not find in undisturbed forests.

 

So how did this myth of taking over forest floors get started? I suspect it’s because people don’t scrutinize what they’re looking at. Garlic Mustard growing along trails into the forest is simply following a cleared pathway of exposed soil. The extent of their spread away from the path depends upon how much the surrounding forest has been thinned (thus allowing sunlight to reach the ground) and whether the soil is covered with enough leaf litter (so soil is not exposed).

 

In other instances, Garlic Mustard spreads where trees exist but aren’t mature enough to create a forest canopy that adequately shades the soil and covers the ground with spent leaves. Many people incorrectly describe such areas as “forest” when they are more properly called “woods”. Terminology matters. If a writer uses misleading words, he misleads his reader—which is archetypal for papers about “invasive” plants.     

 

Now, how about those butterflies being killed in 34 states? Naturally, no reference was supplied by Ms. Roth, the author of the Blue Ridge PRISM “fact” sheet. So, I tried to find this information online.

 

The first paper I looked at was from the Urban Forest Alliance in McLean, Virginia, where the text was identical to that of the PRISM paper. Worse yet, the first suggestion supplied at the end of the paper for “more information” was the PRISM “fact” sheet! As is common with so-called invasive-plant articles by nativist advocates, one paper references another that either replicates exactly the text (as in this case) or repeats the message, albeit in different words. When trying to verify information, you go around in circles because valid information does not exist in articles written by nativist environmentalists.

 

Even when looking at more-recent scientific papers in which references are cited, you often find that the researchers don’t seem to have read them because the papers referenced don’t concur with what the scientists are putting forth. For example, many scientists proclaim that Garlic Mustard is the cause of the decline of the West Virginia White (a butterfly), and virtually all these folks reference a 1971 paper by S.R. Bowden, an English lepidopterist (one who studies butterflies and moths).

 

It took over a year to track down this paper that people greatly reference as providing proof of the toxicity of Garlic Mustard to the West Virginia White’s caterpillar, as well as the supposed ineptitude of the female butterfly by claiming the ovipositing (egg-laying) female often makes the “mistake” of laying eggs on nonnative Garlic Mustard.

 

First, the Bowden paper that gets referenced so often did not prove the female West Virginia White makes the “mistake” in the natural world of laying eggs on Garlic Mustard, a plant that’s not palatable to her larvae. Bowden performed what I’d call, “terrarium science”, in which the female had no choice but to lay her eggs on the plants this man made available to her in an enclosed environment. When you have eggs to lay and your choice is a glass surface or an inappropriate plant, you’re going to hope for the best and go with the plant (your young need to eat, after all).

 

Second, while most people referencing this paper claim the caterpillars were “poisoned” by Garlic Mustard, that is not at all what happened in Bowden’s lab. The caterpillars refused to eat this plant, not unlike a hungry child refusing to eat broccoli! As a result, the caterpillars died from starvation, but the word “poison” connotes evil and is undoubtedly the reason so many native-plant advocates use it when discussing Garlic Mustard and its effect upon the West Virginia White. Always keep in mind: Words matter.

 

References matter, too. I could not find one reference about butterflies being killed by Garlic Mustard in 34 states, nor could I find a reference to particular butterflies other than the West Virginia White (Pieris virginiensis) being threatened by this plant species. Still, a USDA Forest Service document states that Garlic Mustard posed “a severe threat to the long-term survival of the West Virginia White in many areas [throughout much of its historic range]”, yet also clearly declares that “Forest clearing and fragmentation appear to be the greatest threats [emphasis mine] facing this species.”

 https://www.fs.usda.gov/Internet/FSE_DOCUMENTS/fsm91_054237.pdf

 

These folks condemn Garlic Mustard, as if it’s obligatory, despite admitting that other threats to this insect’s existence are far greater. In addition to the loss of habitat due to logging or clearing for agriculture and development, additional menaces include insecticides and herbicides employed in nearby agricultural fields and control efforts for Gypsy Moth outbreaks; deer browsing of native plants; and the effects of climate change (local weather).

 

And another paper, “How Environmental Conditions and Changing Landscapes Influence the Survival and Reproduction of a Rare Butterfly”, points out that even though this butterfly is considered rare, “P. virginiensis is frequently overlooked as it flies early in the spring in forested areas, which are not major sources of butterfly diversity and thus are not often regularly monitored” by butterfly monitoring organizations.

https://www.researchgate.net/publication/271765723_How_Environmental_Conditions_and_Changing_Landscapes_Influence_the_Survival_and_Reproduction_of_a_Rare_Butterfly_Pieris_virginiensis_Pieridae

 

Obviously, employment of the West Virginia White to disparage Garlic Mustard exemplifies what goes on in “invasive-plant” bashing. First, a likeable “victim” (that may not actually be a victim) is found that will (presumably) make people care enough to take the desired action (getting rid of an “invasive” plant) to “save” it. Second, accusatory overstatements—employed to implant images in people’s minds that aren’t valid—are boldly put forth with very little evidence provided to back them up. Dishonesty is the hallmark for how nativists manipulate people to do their bidding.

 

In summary, lies (about alien plant species), hearsay (from other nativists), and ignorance (a lack of true botanical knowledge) form the basis of the “invasive-plant” movement.

NATURE ADVICE:

When people have an agenda, you need to be wary of their words. Don’t just buy into what you read or hear. Make your own observations of so-called invasive plants to find out if our wildlife makes use of them and how so, and if research papers are referenced by native-plant advocates, be sure to look them up. These papers often do not corroborate the claims nativists make.

 

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