herbarium

Collected on September 8, 1991, this specimen was found near Tarentum, Pennsylvania 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 United States until even more recently.  Some suggest it invades more aggressively than its parents.

Most specimens in Carnegie Museum of Natural History’s herbarium were originally identified as Japanese knotweed. Last year, Allison Cusick, a research associate at the museum, went through all 212 knotweed specimens and re-identified many as the hybrid. In fact, only three of the specimens from
Allegheny County were identified as Japanese knotweed!

All three knotweeds collected at the same site near the Allegheny River and Barking Slopes Conservation Area, New Kensington/Plum, Pennsylvania.  

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Botanists at Carnegie Museum of Natural History share pieces of the herbarium’s historical hidden collection on the dates they were discovered or collected. Check back for more!

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 Carnegie Museum of Natural History.

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Botanists at Carnegie Museum of Natural History share pieces of the herbarium’s historical hidden collection on the dates they were discovered or collected. Check back for more!

Collected on April 12, 1919, this specimen was found by Otto Jennings “North of Saunders” in Allegheny County. Jennings was an extremely influential botanist, focusing on nearly all aspects of plants in our region. He made many contributions throughout his career, serving as the curator of botany, director of education, and eventually director of Carnegie Museum of
Natural History. He was also a professor and head of the Department of Biological Sciences at the University of Pittsburgh and advised many students. His legacy is his influence on the museum, botany, conservation, and environmental education.

Skunk cabbage grows in wet, forested areas across the eastern United States.  Although easily overlooked, it is one of the
earliest plants to flower in our region. Its flowers produce heat that melts the snow around it. The flowers smell like rotting meat, which attracts the flies that pollinate it. As the name suggests, the leaves smell like skunk when they are crushed.

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Botanists at Carnegie Museum of Natural History share pieces of the herbarium’s historical hidden collection on the dates they were discovered or collected. Check back for more!

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 a 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 of Natural History’s Herbarium includes 36 specimens from his collections, each over 180 years old.  If you thought your handwriting was hard to read, check out the label in the lower right!

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Botanists at Carnegie Museum of Natural History share pieces of the herbarium’s historical hidden collection on the dates they were discovered or collected. Check back for more!