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.
Kudzu is one of the more well-known weeds, at least by name, sometimes known as “the vine that ate the South.” Collected on October 13, 1997, this specimen was found by Sue Thompson and Bonnie Isaac near the I-376 Squirrel Hill tunnel, Pittsburgh. Kudzu (Pueraria lobata) was introduced to the US as an ornamental in 1876 at the Centennial International Exhibition in Philadelphia. The vine was initially prized in the South to provide shade. The vine was later promoted for use in erosion control. Although listed as a noxious weed in PA, it is more invasive in southern states. There, it has been estimated to spread at a rate of 2,500 acres per year (some say up to 150,000 acres per year, although this estimate has been questioned). Infestations of this plant undoubtedly causes ecological and economic damage.
Below is another specimen of kudzu, collected in its native range in Japan in 2002. Although plants are collected in both native and invasive ranges, few studies have compared specimens of the invasive species across continents.
Nancy Hanks Lincoln (mother of Abraham Lincoln) died on Oct. 5, 1818 from “milk sickness.” Milk sickness is caused by poisoning after drinking milk from cows that have eaten the plant white snakeroot (Ageratina altissima). Also known as “puking fever” or simply “the trembles,” early European-American settlers in the Midwest initially thought milk sickness was an infectious disease. It was soon realized that the unidentified illnesses were caused by drinking milk from cows that ate white snakeroot, which contains the chemical tremetol, a toxin which causes weakness, pain, vomiting, abdominal pain, and can lead to coma and death. The cattle of these early settlers often wandered into the forest to graze, seeking additional forage outside limited pastures. However, milk sickness is very uncommon today due to modern farming practices and cows rarely have access to eat this plant.
White snakeroot is a fall blooming, shade-tolerant species found in forests across the Eastern US, and commonly found throughout southwestern PA. This specimen pictured was collected in 1998 in southwestern Indiana, about 90 miles north of the Little Pigeon Creek Community, where Abraham Lincoln’s family lived.
white snakeroot at Trillium Trail, Fox Chapel Borough, PA (Allegheny Co.); Sept. 19, 2016
Another fall blooming aster! Collected on October 6, 1896 (same year Carnegie Museum was founded!), this specimen was found by early museum botanist John Shafer on Jack’s Island, a small island on the Allegheny River (between Harrison Twp and city of Lower Burrell). Despite the name, New England aster can be found across eastern North America. Along with many other species in the genus Aster, this species was recently reclassified in the Symphyotrichum genus. Symphyotrichum novae-angliae is a perennial (lives for several years) with beautiful deep blue-purple flowers. Like other plants in the sunflower family (Asteraceae), the “flowers” are actually a cluster of flowers (heads) composed of many flowers, with “ray” and/or “disk” flowers.
Photo (above): View of Jack’s Island from Braeburn (Lower Burrell), PA. New England aster might still be on the island, but note the dense stands of invasive giant knotweed that now lines the river and island. Introduced to the US as a garden plant in 1894, Giant knotweed (Fallopia sachilinensis) was not yet in our area when this aster specimen was collect in 1896. Given his thorough collections, we can be almost certain John Shafer would have collected it if it was.
Not all plants in our area photosynthesize! Collected on September 29, 2007, this specimen was collected by Loree Speedy in dry woods in Burrell Township, Indiana County, PA (near Blairsville). Often mistaken for a fungus, Monotropa uniflora, commonly known as the “ghost plant” or “Indian pipe,” is indeed a flowering plant in the blueberry family (Ericaceae). When alive, the plant is white (hence the name “ghost plant”), but turns black when dried. It lacks the green chlorophyll pigments of most plants, and therefore does not make its own sugars through photosynthesis. Instead, Indian pipe is a heterotroph. Like humans, heterotrophs ingest or absorb carbon necessary for life from organic sources, rather than fixing carbon from atmospheric carbon dioxide through photosynthesis). More specifically, this plant is a myco-heterotroph. The way this plant gets its food is incredible. It parasitizes mycorrhizal fungi in the soil. And where does the mycorrhizal fungi get its food? These fungi form a close relationship (symbiosis) with many forest trees, shrubs and herbs, where the fungi aid the host plant in water and nutrient uptake and the fungi receive sugars from the plant in return. This complex relationship was shown using radioactive carbon dioxide, tracking “tagged” carbon molecules from a host tree to Indian pipe. So…ultimately, the food for this non-photosynthetic plant comes from other plants in the forest!
North America used to have over 150 species in the genus, Aster. But now only one species remains. That isn’t because they went extinct, but instead, they were re-named. Many of these species are still referred in general as “asters.” Collected on September 22, 1900, this specimen was found in Fern Hollow, Frick Park, Pittsburgh by early museum botanist John Shafer. Eurybia divaricata (formerly Aster divaricatus) is commonly known as “white wood aster.” This beautiful fall blooming plant (like many asters) is a common native in eastern US forests. So why the new name? Taxonomy (the science of classifying organisms) is an ever-changing science, subject to revision as more research is done, especially at the molecular (DNA) level. As we understand how organisms are related, we can better understand the history of life on earth. Taxonomic studies of plants often lead to splitting of one species into many or the lumping of many species into one. In some cases, a “new” rare species may be have been hiding under our noses, previously grouped with another species. These studies are important for the conservation and protection of vulnerable species. We must know what these species are to actually protect them!
Like most herbaria (plural for herbarium), the Carnegie Museum herbarium is organized by genus within families. Earlier this year, collections manager Bonnie Isaac and a team of interns and volunteers reorganized the sunflower family (Asteraceae), one of the largest families of flowering plants. After a month of reorganizing and renaming folders, the work is still ongoing. No surprise, as this family is represented by over 51,000 specimens (or about 10% of the entire collection)! Ongoing taxonomic rearrangements like these are just one reason why the work of herbarium staff is never done.
Photo above: White wood aster blooming on August 31, 2017 at Fern Hollow, Frick Park (same location as specimen pictured).
It is that time of year when old fields across western PA are painted yellow. Collected on September 15, 1946, this specimen was found in New Baltimore, Somerset county, PA by an influential Curator of Botany at the museum, Otto Jennings. There are many species of goldenrod (in the genus Solidago) in our region. They are often associated with runny noses and sneezing from fall allergies (hay fever), but don’t blame the goldenrods! Their relatively heavy pollen rarely becomes air-borne, but rather these plants are insect-pollinated. Wind-pollinated species, like ragweed, are more likely your culprit.
This specimen pictured here (split between two herbarium sheets) is Canada goldenrod (Solidago canadensis). Canada goldenrod is a fall blooming native species common throughout western PA. However, it was introduced to Europe and Asia for use in floral arrangements and gardens, and has since become an invasive weed in other parts of the world.
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 September 1, 2005, this specimen was found in a floodplain forest near the Monongahela River in New Eagle, PA (Washington county). Ironweed (which includes many species in the genus Vernonia) is a great plant for native pollinators. Consider adding it to your garden! This species of ironweed, known as “tall ironweed” (Vernonia gigantea), can be 2-7 feet tall (or sometimes more than 10 feet!) with beautiful purple flower heads from mid-late summer. Learn more about ironweed (and see it all year long) in Botany Hall at the Carnegie Museum of Natural History.
Collected on August 26, 1998, this specimen was found along a gravel road not far from Settlers Cabin County Park. Ragweed is a plant many people are (all too) familiar with. Or at least their bodies are. Common ragweed (Ambrosia artemisiifolia) is native to North America, but has been introduced across the world. In many cases, this plant (or other ragweed species) are to blame for seasonal pollen allergies known as “hay fever.” In summer and early fall, ragweed plants produce copious numbers of pollen grains, which are dispersed in the wind.
Although ragweed is native in the US, historical records (pollen deposited in sediment cores) suggest that this species was far less common in North America before European colonization. This is perhaps not too surprising considering the species thrives in disturbed habitats that came with European colonization and urbanization. A study published in 2014 by Martin and colleagues in the journal Molecular Ecology extracted DNA from nearly 500 historic herbarium specimens dating back to the 1800s to measure the genetic makeup prior widespread changes to the landscape in the late 19th century. Combined with data from recent collections, they found shifts in the genetic makeup of ragweed populations as the species was expanding in the United States.
Collected on August 18, 1941, this specimen was found just outside of Philipsburg, PA (Centre county) by Leroy Henry. Bull thistle (Cirsium vulgare) is a European plant introduced in PA, commonly found in disturbed sites, roadsides, and fields. As the species is unpalatable to most grazing livestock, bull thistle is often in abundance in grazed fields. It is not uncommon to find American goldfinch pecking at thistle flowerheads, eating the seeds. Recognizable by their spiny stems and flowers (usually purple), thistles are in the sunflower family (Asteraceae), many of which are native to the US.