Collected on this day...
a weekly blog featuring specimens in the Carnegie Museum's herbarium.
each specimen has an important scientific and cultural story to tell.
each specimen has an important scientific and cultural story to tell.
You can get to see plants from all over the world without ever leaving the herbarium. Herbaria are powerful resources that enable research that would otherwise not be possible, comparing plant species collected from across the world, at different times of year.
This specimen of Japanese knotweed (Fallopia japonica, formerly known as Polygonum cuspidatum) was collected in China on Sept 14, 1989 by Q.X. Wang and J.L. Sun.
Even if you’ve never been to East Asia, this species might be familiar to you. Although native to China, Japan, and Korea, Japanese knotweed is now common across much of the temperate world, including the United States and Europe. In Pittsburgh, Japanese knotweed (and related introduced knotweed species) form dense stands along rivers, streams and roadsides.
Specimens collected from both the native and introduced ranges can be compared to better understand plant invasions. For example, do invasive species look the same in their home range?
Although Collected On This Day posts tend to be biased towards specimens collected in Pennsylvania, the Carnegie Museum herbarium includes specimens from many countries across the world. In fact, about 1/3 of the 530,000+ specimens are from outside the United States.
How do these species from far away regions end up at the Carnegie Museum? Many are from expeditions from botanists affiliated with the museum – much in the same way locally collected specimens become part of the collection. But many others are obtained through exchange with other herbaria. Many plant collectors often collect duplicate specimens to send to several herbaria. Most herbaria have exchange programs, where specimens (usually duplicates) are exchanged between institutions. This practice functions to build the collection to include new species and specimens. But it also has an important function to safeguard the future of the data. In the case of damage (such as pest outbreaks or even fire, in the recent devastating case at the Museu Nacional in Brazil), having specimens spread across several institutions helps ensure the future of specimens.
Note the label on this specimen shows this specimen was at one time associated with the herbarium of the Shanghai Museum of Natural History.
47 of the 96 specimens of Japanese knotweed in the Carnegie Museum’s herbarium were collected outside of the United States.
Celebrating the weed that engulfed western Pennsylvania?
Knotweeds collected at the 7th Annual Knotweed Festival in Blairsville, Pennsylvania.
Banks along Conemaugh River, August 11, 2018.
Left: Giant knotweed (Fallopia sachalinensis); Right: Bohemian knotweed (Fallopia x bohemica).
A few weekends ago, I went to the 7th annual Knotweed Festival in Blairsville, about 40 miles east of Pittsburgh in Indiana County. Aside from reading a brief advertisement, I knew little about the festival before going. But, given I study non-native plant invasions, I had to go to a celebration named after a local weed that is a focus of my research! And this invader is one of the most aggressive and widespread ones in western Pennsylvania – Japanese knotweed.
Native to East Asia, Japanese knotweed (Fallopia japonica) is a large herbaceous perennial that was first introduced as to the U.S. in the late 1800s as an ornamental. As its name suggests, it eventual spread well outside of gardens to become a major nuisance. More troubling, the spread of the species displaces native vegetation and disrupts the natural function of the ecosystem. The plant has thick hollow stems that somewhat resemble bamboo, although they are not related (knotweed is in the buckwheat family, Polygonaceae; bamboo in the grass family, Poaceae). Knotweed spreads through persistent belowground structures called rhizomes (belowground stems), as well as by seed. Small fragments of rhizomes can be washed downstream and easily establish, often forming dense stands along Pittsburgh’s many streams and rivers. Knotweed is among the most economically and ecologically problematic invasive plants in Pennsylvania.
So, why name a community festival after this invasive plant?! Despite the dislike for the plant, the community of Blairsville named the festival partly as a tongue-in-cheek sentiment for the plant that has taken over the landscape and partly to recognize the weed as embedded into the local culture. The nearby Conemaugh River that runs throughs Blairsville has been transformed by this non-native species, completely covering the banks with stands so dense they completely block the view of the river along the community recreational trail.
My family and I had a great time at the festival, visiting local craft and food vendors, musicians and other entertainment, a monarch butterfly display, and complete with a parade. I even bought soap made from the rhizomes and stems of knotweed collected by the river.
At first, I had mixed feelings about naming a festival after an aggressive invasive plant known to cause ecological harm. On one hand, it embraces the nature around us – whether we like it or not, non-native plants are part of the landscape around us. The global movement of plants around the globe is one of the defining features of the Anthropocene, the current era of pervasive human influence on the environment and Earth’s systems. But, on the other hand, naming a festival after an invasive species normalizes plant invasions and perhaps even embraces the change to the landscape as a good thing. Despite my initial mixed feelings, I think the festival is a great community gathering that has the potential to raise awareness about the presence of the invasive plant in our community, its ecological effects, and in turn, nature around us (native and non-native).
It turns out there are more than one species of invasive knotweed in western PA: Japanese knotweed (Fallopia japonica), Giant knotweed (Fallopia sachalinensis), and a hybrid between the two species, Bohemian knotweed (Fallopia x bohemica). The hybrid was only recognized in the past several decades and likely originated when these two species “met” after they were introduced in Europe. The three species are visually similar. Giant knotweed can be distinguished by its large (usually much larger than your hand), heart-shaped leaves. Japanese knotweed and the hybrid Bohemian knotweed are much more difficult to distinguish, with much variation in leaf shape. Japanese knotweed tends to be rounder in shape, while the Bohemian knotweed is intermediate between the other two species in leaf shape and size. The leaf hairs are sometimes the only definitive identifying feature.
Image below: Last year, I found all three knotweed species growing together at the same site near the Allegheny River and Barking Slopes Conservation Area, near New Kensington/Plum, PA. Left to right: Japanese knotweed (Fallopia japonica), Bohemian knotweed (Fallopia xbohemica), Giant knotweed (Fallopia sachalinensis).
While I was at the Knotweed Festival, I collected some knotweed specimens for the Carnegie Museum’s herbarium. Along the Conemaugh River in Blairsville, I collected both the Giant knotweed and Bohemian knotweed (the hybrid). But, I did not find any Japanese knotweed. (I suspect my knotweed soap is actually made from Giant knotweed, after all.)
The earliest herbarium specimens from Indiana County were collected in 1952 along the Conemaugh River in Saltsburg (not far from Blairsville). Interestingly, these specimens were of Giant knotweed and Bohemian knotweed – the same species I collected.
Keep an eye out for knotweed.
If you live in western PA, chances are that you see it every day!
Collected on September 8, 1991, this specimen was found near Tarentum, PA by Walt Zanol. If you had to pick the most aggressive invasive plant in the Pittsburgh area, knotweed would be among the top choices. This particular specimen is Bohemian knotweed (Fallopia xbohemica), a hybrid between giant knotweed (Fallopia sachalinensis) and Japanese knotweed (Fallopia japonica). Japanese knotweed was introduced from East Asia and Giant knotweed came from Sakhalin (Russia). The hybrid likely originated when these two species “met” after they were introduced in Europe. Both species and their hybrid can be found around Pittsburgh, often in enormous dense clusters along highways and waterways. Take note on your drive to work or walk in the neighborhood – knotweeds are all around!
Giant knotweed is distinguished by its large (usually much larger than your hand), heart-shaped leaves. Japanese knotweed and the hybrid Bohemian knotweed are much more difficult to distinguish, with much variation in leaf shape. In fact, the hybrid was only recognized in the early 1980s and was largely overlooked in the US until even more recently. Some suggest it invades more aggressively than its parents. Most specimens in the Carnegie Museum of Natural History’s herbarium were originally identified as Japanese knotweed. Last year, Allison Cusick, Research Associate in Botany at the museum, went through all 212 knotweed specimens and reidentified many as the hybrid. In fact, only 3 of the specimens from Allegheny county were identified as Japanese knotweed!
For more info, see Zika & Jacobson (2003) Rhodora 105:143-152. https://www.jstor.org/stable/23313523?seq=1#page_scan_tab_contents
All three knotweeds collected a couple weeks ago at the same site near the Allegheny River and Barking Slopes Conservation Area, New Kensington/Plum, PA. Left to right: Japanese knotweed (Fallopia japonica), Bohemian knotweed (Fallopia xbohemica), Giant knotweed (Fallopia sachalinensis).
Collected on March 10, 1830, this specimen was found by Nathaniel Wallich, probably in India. Polygonum chinense is also known as Chinese knotweed, although there are several species with that common name. This species is in the same family as many familiar plants, including Japanese knotweed, which is widespread invasive plant in our area.
Nathaniel Wallich (1786-1854) was an influential botanist from Denmark who worked much of his life in India. Carnegie Museum’s Herbarium includes 36 specimens from his collections, each over 180 years old.
And if you thought your handwriting was hard to read, check out this label!