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Uprooted

April 19, 2024 by Erin Southerland

City Nature Challenge: Noticing Invasive Plants 

by Rachel Reeb and Jessica Romano

This spring, thousands of people will join the City Nature Challenge, a global effort to document biodiversity safely and easily on the free iNaturalist app. Participating in the challenge is fun and rewarding – simply make observations of nature, take photos, and upload them to the app. The data collected during the challenge is shared with scientists around the world and helps them both document and better understand the diversity of species around us. This year’s challenge takes place April 25 through 28 for the observations, with a follow-up identification period from April 29 through May 1 when scientists and naturalists help observers properly identify the species they found. Participants will observe plants, insects, mammals, birds, mollusks, reptiles, amphibians, and more, right in their own neighborhoods. 

Alliaria petiolate, common name Garlic Mustard, is very commonly spotted during the City Nature Challenge and is easy to identify by its broad leaves and small white flowers. Credit: Katja Schulz from Washington, D. C., USA, CC BY 2.0, via Wikimedia Commons.

To help get us ready for this year’s challenge, Rachel Reeb, postdoctoral fellow in the Section of Botany at Carnegie Museum of Natural History, created this guide to finding and understanding invasive species of plants, including species like garlic mustard that is repeatedly one of the most often observed plants during the challenge. To get started, Rachel provided helpful definitions: 

Native or Indigenous species: Species that exist within an area due to natural evolution.

Introduced species: Species that have been introduced, by humans, to an area outside of its indigenous range. Roughly 25% of plant species in our environment are introduced.

Invasive species: A subset of introduced species which cause significant harm to the environment or human well-being. 

Naturalized species: A subset of introduced species which do not have demonstrated impacts on the environment or human well-being.

Lonicera maackii, known as the Amur Honeysuckle, originated in temperate areas of eastern Asia. Credit: Jay Sturner from USA, CC BY 2.0, via Wikimedia Commons.

Observing Invasive Plants

When is the best time to spot invasive plants? In the early stages of spring! Since introduced invasive plants evolved in a different part of the world, they often have unique life cycles that start and end at a different time than the rest of the plant community. Invasive species like garlic mustard, lesser celandine, periwinkle, multiflora rose, and Amur honeysuckle are some of the first to start their life cycles in the spring, providing a surprising pop of greenery to an otherwise dormant forest understory. This ‘head start’ in the growing season gives invasive plants an advantage because they gain priority access to soil nutrients and sunlight, while other plants are still dormant. 

Ficaria verna, or Lesser Celandine, blankets the ground in Frick Park. Credit: Rachel Reeb.

Unfortunately, what serves as an advantage for invasive plants is often a disadvantage to their neighbors, which now have a delayed start in the race to capture limited seasonal resources. Environmental experts in Pittsburgh are especially worried about the survival of rare native wildflowers, such as large white trillium, mayapple, and yellow trout lily. These plants, which have very specific habitat conditions and cannot easily relocate to new areas, are highly sensitive to changes in the environment and often cannot survive in areas where invasive plants are present.

During this year’s City Nature Challenge, we encourage you to take note of everything in nature, including the weeds. What do you notice about invasive plants in your area, like the timing of their life cycle, or how they interact with their neighbors? Have you ever wondered how these organisms came to be here? Many unwanted invasive plants were first introduced as popular garden center products. While some invasive species are now banned from sale, many can still be found in stores, like English ivy and Periwinkle vines.

Podophyllum peltatum, common name Mayapple, is a native species in Pennsylvania and sprouts early in spring, resembling little umbrellas on the landscape. Credit: Jessica Romano.

Here are helpful lists of species you may encounter in our area:

Invasive Species

  • Garlic Mustard 
  • Lesser Celandine
  • Knotweed 
  • Multiflora Rose
  • Amur Honeysuckle
  • Periwinkle / Vinca 
  • English Ivy 
  • Japanese Barberry 
  • Tree of heaven

Naturalized Species

  • Common Dandelion
  • White Clover

Native Spring Wildflowers 

  • Mayapple
  • Large White Trillium
  • Dutchman’s Breeches
  • Virginia Bluebells
  • Common Blue Violet
  • Yellow Trout Lily

How many of these species can you spot? Get your camera/phone/device and join the City Nature Challenge, April 25 through 28!

Rachel Reeb is a postdoctoral research fellow in the Section of Botany at Carnegie Museum of Natural History. Jessica Romano is Museum Education Writer at Carnegie Museum of Natural History.

Related Content

What’s in a Name? Japanese Knotweed or Itadori

Snags, Logs, and the Importance of a Fallen Tree

Using iNaturalist in the City Nature Challenge and Beyond

Filed Under: Blog Tagged With: Botany, City Nature Challenge, Education, Jessica Romano, Rachel Reeb, Uprooted

November 30, 2023 by Erin Southerland

What’s in a Name? Japanese Knotweed or Itadori

by Rachel Reeb
hand holding a Japanese knotweed plant

We name what we notice, adopting or creating vocabulary to reflect all that our senses regularly engage.

Where multiple names exist in the same language for the same subject, nuance reigns. In Japan, for example, a historical collection of words referring to Reynoutria japonica (synonym: Fallopia japonica), the plant known commonly as itadori or Japanese knotweed, totaled to 689 terms. Some words referenced the plant’s shape and structure, others its sour taste, medicinal properties, seasonal appearance, or supporting habitat. Several dozen terms even noted audio characteristics, referencing the sound produced by the snapping of the plant’s stem.

Though the plant has deep cultural and ecological ties to its home range of Japan, Taiwan, China, and Korea, most of these connections are lost in its introduced range of western Pennsylvania, where it is considered to be an unwelcome invasive species. Information about how differently itadori is regarded in different parts of the world forces us to appreciate the diversity of human attitudes towards plants. Why are plant species perceived positively by some people, but negatively by others? To explore this question, a research paper documenting the rich cultural and ecological history of itadori in Japan (“Fallopia japonica (Japanese Knotweed) in Japan: Why Is It Not a Pest for Japanese People,” M. Shimoda and N. Yamasaki, 2016) made the journal club reading list for the scientists and educators involved in the collaborative Invasive Plant Species Education and Outreach Campaign funded by the Richard King Mellon Foundation.

Along the Allegheny River near Braeburn, Westmoreland County, spring growth of a knotweed stand that will block the view of the water by late June.

Itadori, or Japanese knotweed, has co-evolved with the humans, plants, and animals living in its home range for thousands of years. It’s no wonder that there are so many names for this plant in Japan, where people have co-existed with itadori and passed down their knowledge of the species over generations. Throughout history, humans found many uses for itadori in food, medicine, floral arrangements, and even as a children’s toy! 

Today, in Japan, itadori commonly grows around lawns and roadsides, but it is not considered to be a pest because it can easily be mowed and managed. In comparison, itadori was introduced to western Pennsylvania in the early 1900s, making our collective experience with the plant relatively recent by botanical standards. 

People widely planted itadori in ornamental gardens across the continent, but did not anticipate that it would escape cultivation and become established in nature. Here, many of the natural ‘checks and balances’ that stabilized itadori populations in the home range have been lost, including its insect pests, fungi, and plant competitors. Humans also lack deep ties to itadori in the introduced range, and consider it to be more detrimental than it is useful. The fast-growing plant often causes structural damage to buildings, is extremely expensive to manage, and displaces many of the native plants and animals we have formed connections with.

Thousands of years from now, itadori is likely to form new ecological and cultural connections in its introduced environment of Pennsylvania. What new names might we use to describe it, as our relationship to this plant evolves over time?

Rachel Reeb is a postdoctoral research fellow in the Section of Botany at Carnegie Museum of Natural History and content creator and project manager for the Invasive Species Awareness Campaign.

Related Content

Celebrating the Weed That Engulfed Western Pennsylvania?

Collected On This Day in 1989: Japanese Knotweed

Collected On This Day in 1930: Common Reed

Carnegie Museum of Natural History Blog Citation Information

Blog author: Reeb, Rachel
Publication date: November 30, 2023

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Filed Under: Blog Tagged With: Botany, Rachel Reeb, Science News, Uprooted

November 1, 2022 by Erin Southerland

The Vine That Ate Pittsburgh? Not yet.

by Mason Heberling
herbarium sheet specimen of kudzu

This specimen of Kudzu (Pueraria montana var. lobata) was collected on October 28, 1920 by Neil McCallum at West End Park, Pittsburgh. The plant was collected in cultivation, meaning it was intentionally planted and grown in a garden or similar managed landscape. This specimen is one of the earliest records of the species in Pittsburgh. (It was also collected two years before).

kudzu flower

Kudzu is a vine in the bean family, Fabaceae, with beautiful purple flowers. Native to East Asia, it was introduced as an ornamental plant to the United States from Japan in 1876 at the Philadelphia Centennial Exposition. It was promoted in the 1930-40s in the southern US to prevent soil erosion. However, it is now an invasive species, with big ecological impacts. It is widely known as “the vine that ate the South.”  A quick Google search will show you striking pictures of the vine covering large areas of land, covering trees, shrubs, logs, and anything else in the path of its explosive growth. Kudzu shades out existing vegetation and can drastically alter the ecosystem.

kudzu under telephone wires


It is not common in Pennsylvania, but perhaps might become so.  Kudzu is listed by the state as a “Class A Noxious Weed” – meaning it is assessed as a high invasive risk and ecological/economical concern, but is uncommon and possible to be eradicated.  It cannot be sold or planted commercially in Pennsylvania.

It is currently most invasive in the South, but a study published in 2009 by Dr. Bethany Bradley and others suggests that the species may become more invasive in the north (including Pennsylvania) as climate change continues.


You can find this specimen online here, and search our collection at midatlanticherbaria.org.

Mason Heberling is Assistant Curator of Botany at Carnegie Museum of Natural History. 

Related Content

Collected on this Day in 1951: Bittersweet

Collected on this Day in 1930: Native…or Not?

Collected on this Day in 1995: Ragweed

Carnegie Museum of Natural History Blog Citation Information

Blog author: Heberling, Mason
Publication date: October 28, 2022

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Filed Under: Blog Tagged With: Botany, collected on this day, liocf, Mason Heberling, Uprooted, We Are Nature 2

January 11, 2022 by Erin Southerland

Collected on this Day in 1951: Bittersweet

by Mason Heberling
Bittersweet plant in spring

Leaves are gone, but fruits hang on

Bittersweet plant specimen on herbarium sheet

This specimen of bittersweet (Solanum dulcamara) was collected by Bayard Long on January 11, 1951 in a “rubbish dump” on West Chester Pike, near Broomall, Pennsylvania (outside of Philadelphia). Bayard Long (1885-1969) was a Philadelphia-area botanist and an active member of the Philadelphia Botanical Club (founded in 1891 and still an active organization). He was a prolific collector and for 56 years served as Curator of the Club’s Local Herbarium, which is housed at the Academy of Natural Sciences. 

Bittersweet nightshade (Solanum dulcamara) is in an herbaceous vine in the potato or nightshade family (Solanaceae), not to be confused with the similarly named Asian bittersweet (Celastrus orbiculatus), which is also a woody vine in the staff vine or bittersweet family (Celastraceae).

Bittersweet is an invasive species, introduced from its native range in Europe and Asia as early as the 1800s. It is common to see climbing along fences in urban areas and elsewhere across North America.

In the winter, its fleshy red berries are commonly still attached to the vines, long after the leaves are gone.

bittersweet plant in the fall

Find this specimen of bittersweet. 

Check back for more! Botanists at the Carnegie Museum of Natural History share digital specimens from the herbarium on dates they were collected. They are in the midst of a three-year project to digitize nearly 190,000 plant specimens collected in the region, making images and other data publicly available online. This effort is part of the Mid-Atlantic Megalopolis Project (mamdigitization.org), a network of thirteen herbaria spanning the densely populated urban corridor from Washington, D.C. to New York City to achieve a greater understanding of our urban areas, including the unique industrial and environmental history of the greater Pittsburgh region. This project is made possible by the National Science Foundation under grant no. 1801022.

Mason Heberling is Assistant Curator of Botany at Carnegie Museum of Natural History. Museum employees are encouraged to blog about their unique experiences and knowledge gained from working at the museum.

Related Content

Plants with Bladders?

Collected on this Day in 1998: Common Chickweed

Collected on this Day in 1925: A Flower with No Leaves?

Carnegie Museum of Natural History Blog Citation Information

Blog author: Heberling, Mason
Publication date: January 11, 2022

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Filed Under: Blog Tagged With: Botany, Mason Heberling, Science News, Uprooted, We Are Nature 2

November 12, 2021 by Erin Southerland

Collected on this Day in 1930: Native…or Not?

by Mason Heberling

Though the supercontinent Pangea broke apart many millions of years ago, the Anthropocene is marked by a new kind of Pangea. The globalization of human activities has brought species from around the world into contact which otherwise would never interact. Though the seven continents as they are today may not be physically connected into a single landmass, they are perhaps more connected than they have ever been. 

Some species are intentionally moved from one continent to another, such as the plants in gardens, while other introductions are accidental, mere unintentional passengers of humans increasingly global activities. Introduced species can fundamentally alter the landscape and are regarded as one of the top threats to native biodiversity.

Invasive species are those introduced species which are non-native and spread without human intervention. Many invasive species alter ecosystem functioning and change regional biodiversity. Invasive plant species have become a common part of our landscape. Some were brought over hundreds of years ago by European colonists. Others have arrived much more recently. 

In Pennsylvania, the invasion of some plant species is obvious – that is, a unique species arrives, thrives, and become abundant. These invasive species have no record of being in the area and can spread rapidly, sometimes over the course of a human lifetime or shorter. Many invasive species are still actively spreading across the landscape. For instance, garlic mustard (Alliaria petiolata) is a well-known forest herb from Europe introduced to North America in the mid-1800s. After more than a century, the plant is now common across Pennsylvania’s forests. Another obvious example is giant knotweed (Reynoutria sachalinensis), a native to parts of East Asia, first recorded in western Pennsylvania in the 1920s, and since spread to line many of Pennsylvania’s rivers and streams. You can’t go far in the Pittsburgh region without seeing invasive knotweed.

Other species invasions are less obvious. These so called “cryptic invasions” are the introductions of very closely related species or subspecies which originated elsewhere. 

specimen of common reed on an herbarium sheet

This specimen of common reed (Phragmites australis) tells the tale of a widespread cryptic invasion. The specimen was collected by Carnegie Museum botany curator Otto Jennings on November 2, 1930 along the shores of Lake Erie at Presque Isle, Pennsylvania. Common reed is a major problematic invasive species, crowding out native species in this unique habitat at Presque Isle. When this specimen was collected over 90 years ago, it was not nearly as abundant as it is now. 

common reed plants with trees outside
A large stand of Phragmites at Presque Isle State Park, August 2019.

But is it non-native? Common reed, or often simply called Phragmites, has a very widespread distribution, found in wetlands and shores across all continents except Antarctica. It is even a common site along wet areas near highways. Common reed is among the most widely distributed plants in the world.

Reed is non-native to the United States…well, mostly. In the 1800s, botanists considered Phragmites to be a relatively uncommon plant. Evidence from fossils and paleoecological research show that the species has indeed been in North America for many thousands of years. However, it didn’t start to become abundant until the early 1900s and after. Some botanists suggested the sudden success of the species could be due to human disturbance.  A pioneering herbarium-based study from 2002 published in PNAS by Dr. Kristin Saltonstall sequenced DNA from herbarium specimens collected before 1910 and recent collections to show that the spread of Phragmites in the United States was due to the introduction of a non-native strain of the species that originated from Europe. 

Pretty cool, huh? And this finding was made possible with herbarium specimens.

So, is this particular specimen native or not? I don’t actually know, but with expert examination and genetic analysis, we could find out! 

Find this specimen and 149 more in the Carnegie Museum herbarium here.

Check back for more! Botanists at the Carnegie Museum of Natural History share digital specimens from the herbarium on dates they were collected. These scientists are in the midst of a three-year project to digitize nearly 190,000 plant specimens collected in the region, making images and other data publicly available online. This effort is part of the Mid-Atlantic Megalopolis Project (mamdigitization.org), a network of thirteen herbaria spanning the densely populated urban corridor from Washington, D.C. to New York City to achieve a greater understanding of our urban areas, including the unique industrial and environmental history of the greater Pittsburgh region. This project is made possible by the National Science Foundation under grant no. 1801022.

Mason Heberling is Assistant Curator of Botany at Carnegie Museum of Natural History. Museum employees are encouraged to blog about their unique experiences and knowledge gained from working at the museum.

Related Content

The Circle of Life…and Invasion

Ask a Scientist: How do you find rare plants? [Video]

Collected on This Day in 1982: One specimen isn’t always enough!

Carnegie Museum of Natural History Blog Citation Information

Blog author: Heberling, Mason
Publication date: November 12, 2021

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Filed Under: Blog Tagged With: Botany, collected on this day, Mason Heberling, Science News, Uprooted, We Are Nature 2

April 29, 2020 by wpengine

From cultivation to invasion: a common route

Collected on this Day in 1937

This specimen of princess tree (Paulownia tomentosa) was collected on January 13, 1937 in Schenley Park, Pittsburgh by R.J. Templeton and J.R. Steck.  Though subtle, note the heading on the label “Flora of Cultivation.”  This header suggests that this tree was planted in the park, rather than naturally occurring on its own.

Princess tree has a remarkable presence – large wide leaves larger than your face (though you can’t see that in this winter collected specimen) and very showy, fragrant flowers that burst from large buds in the spring.  Signs of the flowers/fruits remain obvious on the branches year round.

Princess tree is a common urban weedy tree that is not native to Pennsylvania or the United States. Rather, it is native to Central and Western China.  It was brought to Europe in the 1830s (and then to the US) by the Dutch East India Company, with many historical medicinal and ornamental uses, as well as its wood. The tree was named after a Romanov princess, the Grand Duchess Anna Pavlovna.

Princess tree can still be found in Schenley Park.  It is especially noticeable, with its flowers at eye level, as you walk or drive across the bridge from the museum to Phipps Conservatory (Schenley bridge).

Listed as invasive by the state, Princess tree should not be planted in Pennsylvania.  It grows quickly and actively spreads beyond its planting, into roadsides, streams, and disturbed forests with potential to displace native plants.

Find this specimen and more here: http://midatlanticherbaria.org/portal/collections/list.php?db=all&catnum=CM120710&othercatnum=1

Check back for more! Botanists at the Carnegie Museum of Natural History share digital specimens from the herbarium on dates they were collected. They are in the midst of a three-year project to digitize nearly 190,000 plant specimens collected in the region, making images and other data publicly available online. This effort is part of the Mid-Atlantic Megalopolis Project (mamdigitization.org), a network of thirteen herbaria spanning the densely populated urban corridor from Washington, D.C. to New York City to achieve a greater understanding of our urban areas, including the unique industrial and environmental history of the greater Pittsburgh region. This project is made possible by the National Science Foundation under grant no. 1801022.

Mason Heberling is Assistant Curator of Botany at the Carnegie Museum of Natural History. Museum employees are encouraged to blog about their unique experiences and knowledge gained from working at the museum.

Filed Under: Blog Tagged With: Anthropocene, Botany, botany hall, collected on this day, Hall of Botany, Mason Heberling, Museum from Home, Uprooted

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