by Amoi Campbell
There is something so terrible and haunting about how knotweed grows in Pennsylvania. Its pale white flowers are a sort of cursed beauty, alluring to human eyes and pollinators alike. On a late summer day you can peer into this world within our own and watch bees, ants, butterflies, and beetles shift from flower to flower of this ominous but beautiful invasive shrub. The clustered spikes of flowers pierce through the emerald green curtain of foliage. Even from a distance the delicate blossoms appear upright and modest. Sightings of white blossoms on the edges of busy streets and forested trails are frequent, giving knotweed an almost omnipresent quality.
The true nature of the weedy thicket reveals itself to those who look closely. In a well-established stand of knotweed, one can note the absence of other plants. There, only knotweed seems to flourish. Creeping into the forest on the sides of creeks, ravines, and trails, knotweed may seem inconspicuous at first.
There is an air of mystery to all the places it sinks its roots into. Strange and unexpected places overwhelmed and overtaken. Whatever grew there before becomes a distant memory of a different time and space.
As knotweed grows it transforms even the soil around it. Taking root where the tree canopy is sparse, and the woods break into clearings or trails. Sometimes it is obvious the site has been disturbed by natural forces or human construction. Under the surface, with worms as witnesses, the seeds or nodes of discord take root in Pennsylvania soil. Knotweed’s monstrous nature lies in its ability to seemingly come back from the dead, cut it down year after year and it will still grow back.
It was a warm day for October, another day in an almost endless summer, when I learned how knotweed grows in Pittsburgh. I was searching for places to sample for my first graduate rotation project in the Kuebbing lab. Jess, the Kuebbing lab manager was accompanying me and helping me throughout this period. We were prepared but not ready for the full extent of this site. From the road we could sense that there was more than what met our eyes. Curious and cautious we decided to inspect the site further. You see, I had just begun to study the knotweed taxa for an ecology project on invasive plants and I was always looking for more knotweed patches. Taking in what I thought was a small 4-meter patch, I grew excited to sample a new location.The further I walked and the closer I looked, I realized I was horribly wrong. This wasn’t a single patch but rather a discontinuous field of knotweed with abandoned buildings and trees sprinkled in. Off that quiet road, Jess and I stumbled upon the ruins of an old church. Jess noted that the once beautiful stained-glass windows had become translucent shards scattered about the unkept yard. The broken windows and dilapidated appearance of the church surrounded by fields of overgrown weeds and strangling vines felt gothic in every sense of the word.
This mysterious scene, set out in front of me, was captivating to me as a researcher and also as a lover of horror stories. To me this was nothing short of a great and terrible thing.
The only places Knotweed was not growing on this street was the mowed edges of the road across from the church. Later, I would discover the true length of the stand. At this point I had only accounted for what was more or less the width. If knotweed could grow there it would grow there. The stalks of Knotweed were breaking apart concrete and the knotweed rhizomes were colonizing the soil deep below. The thickness and strength of those roots gave me pause on multiple occasions. Reading about the roots had not prepared me for the realities of them. It was a strange test of patience realizing we could not dig to collect dirt from the stand to study in the lab later. We were shocked at the revelation there was no soil on the surface, just concrete and a thin layer of dead plant matter resembling dirt. We had been deceived by the decay and disorder brought about by the fallen Knotweed leaves.
While sampling around the sidewalk I could see straight through the empty church’s unhinged doors to the back. It took awhile for my eyes to take it all in but when I glanced over the church again I saw it, it was unmistakable. In the back behind the church I noticed some movement. My eyes focused, the wind was blowing through knotweed.
Walking to the back of this block we found an old cemetery. The well-maintained graves were a stark contrast to the lengthy knotweed patches across the street. By that time the weather turned sour. The air was cool and the sky grey, the warm sun had hidden itself away as I stood next to that graveyard.
I walked that street in awe of the full extent of the knotweed site. I looked around myself eager to share this discovery with Jess, who had begun to capture the moment in photos. On the perimeter of the graveyard was a wall of abandoned headstones, carved with names and dates of those who had already passed. We wandered on a clean empty street across from the cemetery. Someone had taken the time to cut back the overgrowth again, and again. Yet still, on that quiet road the knotweed seemed endless. It felt like it was waiting for us to leave. The knotweed was waiting for us all to leave. Just as the knotweed inherited the church without a watchful groundskeeper to maintain the land, so too would the thicket take whatever else it could take.
I thought I understood what an invasive species was but seeing it in all its rawness was a different story, it was a horror story where few native plants would or even could survive in the end. What sites like this hint at is knotweed’s success at decreasing the diversity of plants native to Pennsylvania. Knotweed establishes early in disturbed or poorly maintained sites. Over time bamboo like stalks can take over and claim the land for its clones. This ecological horror story is not just set on this one lonely dilapidated street in Pittsburgh. It is here in my neighborhood, and if you look closely you might even see it in your own backyard.
Amoi Campbell is a post-baccalaureate fellow at University of Pittsburgh’s Department of Biological Sciences. She earned a B.S. in Biology from Howard University. Amoi's research interest include invasive plants, climate change, plant-plant interactions, plant-soil interactions, and urban ecology.