Mason Heberling

Some dogwoods for the dog days of summer
 
Who doesn’t love a good dogwood? Perhaps you are most familiar with flowering dogwood (Cornus florida), with the beautiful showy white flowers in woods and wooded roadsides across Pennsylvania in the spring.  Or perhaps, the commonly planted Japanese dogwood (Cornus kousa) from...you guessed it...East Asia.  But there are many different dogwood species, all in the genus Cornus.  Species in the genus are distributed across much of the temperate world in the Northern Hemisphere.  Rhoads & Block Plants of Pennsylvania list nine species found in the wild in our state.  They are trees or shrubs (with one exception). The veins on their leaves are quite distinctive, as is their bark and flower structures.
 
Why are these shrubs called dogwood?  There are several stories behind the unique common name. One is that the name was derived from the Celtic word “dag”, referring to its use of its nice wood as a dagger like tools or skewers. Another explanation is that the bard was once used as a treatment of mange for dogs.
 
Four dogwood species were collected on June 28 in Pennsylvania: 69,  37,  26, and 23  years ago:
 
Red-osier dogwood, Cornus sericea (aka Cornus stolonifera) June 28, 1950 in Erie County. Beautiful bright red stems.
 
Gray dogwood, Cornus racemosa June 28, 1982 in Blair County.
 
Cornus ammonum June 28, 1993 in Clarion County.
 
Cornus florida June 28, 1996.  White flowers from the spring are long gone.  (Well, the white structures aren’t actually petals, but modified leaves called bracts that surround a cluster of small yellowish flowers).
 
Over 2,600 dogwood (Cornus) specimens in the Carnegie Museum herbarium from across the world are available online, many with high resolution images: http://midatlanticherbaria.org/portal/collections/list.php?db=328&taxa=cornus&usethes=1&taxontype=2

Whoa, this plant will catch your attention!  Although towering in at up to 8 feet tall with leaves 2 feet wide, Cow parsnip (Heracleum maximum, aka Heracleum lanatum) is not a tree, but herbaceous (non-woody). This species is the largest member of the carrot family (Apiaceae) native to North America. It can be found along shaded roadsides, waterways, and edge of woods. Its flower structure consists of many small white flowers on short stalks connected at a single point – an umbrella of flowers - botanically known as an “umbel.” Umbels are characteristic of the carrot family (think of the perhaps better recognized Queen Anne’s lace, Daucus carota, which is also known as “wild carrot”).
 
These specimens were all collected on June 21– but years apart - on 1907 (Westmoreland county, PA), 1934 (Pittsburgh), and 1960 (Beaver county, PA).   
 
This species is often confused with giant hogweed. Cow parsnip is often confused for the non-native plant called giant hogweed (Heracleum mantegazzianum). Giant hogweed has hit the news media in past few years and on many people’s radar, as it is considered a significant public human health concern. This plant is highly poisonous and designated as a federal noxious weed.  The sap of giant hogweed causes “phytophotodermatitis,” meaning serious skin inflammation occurs when contacted skin is exposed to sunlight.  Skin rashes can be very severe.  The sap can cause temporary or permanent blindness. Cow parsnip has a similar set of chemicals in its sap, and although not as poisonous, be  careful around these plants.
 
Giant hogweed can be 8-20 feet tall with leaves up to 5 feet wide!  It is thought to be eradicated in Pennsylvania. Although similar to the Pennsylvania native species cow parsnip, giant hogweed is noticeably larger in height and flower size. (see herbarium specimen here – it took 6 sheets!)
 
See here for a nice comparison between these similar species. https://www.maine.gov/dacf/php/horticulture/hogweedlookalikes.shtml
 
Given the size of members of the genus, the name Heracleum (derivative of Hercules) is quite fitting.
 
Specimen records and images for this species in the CM herbarium are now publicly available online:
http://midatlanticherbaria.org/portal/collections/list.php?db=328&taxa=Heracleum+lanatum&usethes=1&taxontype=2

Not all bittersweet vines are invasive to Pennsylvania. This specimen was collected on June 14, 1965 by botany curator Leroy  Henry  in Clearfield county,  along  Rt 969. American bittersweet (Celastrus scandens) is a woody vine that  blooms in June, which turn to beautiful clusters of orange/red fruit in late summer/fall.  The species is native to eastern USA, found along open thickets/edge of woods.

American bittersweet (Celastrus scandens) might be easily  confused with the much more common Asian bittersweet (Celastrus orbiculatus).  There are two major visual  differences between the species: 1) flower/fruit --  native species has single terminal cluster of many flowers/fruits at tips of branches, whereas the invasive has flowers/fruits at axils of leaves (where leaves connect to stem; and 2) leaves -- native  species' leaves are more elongate, whereas the invasive species' leaves are more round, often even circular ('orbiculate').

American  bittersweet is no longer common in Pennsylvania, most likely taken over by the closely  related Asian bittersweet.   Asian bittersweet  is a relatively newer addition to the  flora of Pennsylvania, not showing  up  in  western PA and  the  Pittsburgh region until  the 1980s.  Given its abundance and distribution throughout the region  now,  it is hard to fathom it was not present only several decades ago.

Research over the past decade has shown that the invasive species hybridizes with the native, likely contributing to  the decline  of the native American bittersweet.

Keep a look out for American bittersweet in our region.  (I have  not  seen it in Allegheny county, although we have historic  records)

This specimen image is now publicly available online:
http://midatlanticherbaria.org/portal/collections/individual/index.php?occid=12131436&clid=0

This is a special specimen.  The Carnegie Museum herbarium is full of specimens of scientific and historical importance.  And this is a notable one, collected in June 1830 by William Darlington in West Chester, Pennsylvania.  William Darlington (1782-1863) was an important figure in the history of Pennsylvania botany. Darlington was a physician, politician (US House of Representatives 1815-1823),  and as  you might guess – a botanist!  At the University of Pennsylvania, Darlington studied botany under Benjamin Smith Barton, a well-known botanist who also trained Meriwether Lewis (of the Lewis & Clark Expedition). Darlington wrote several He spent most of his life in West Chester, PA. He wrote some of the earliest botanical works, including a flora of Chester County in 1826 and others on agriculture.  Many of his specimens are among the earliest documentation of Pennsylvania’s flora and are preserved in the William Darlington herbarium at West Chester University.
 
This particular specimen is of the native shrub Euonymus americanus, commonly called “strawberry  bush.”  Despite the name, it is not related to strawberries, but in the bittersweet/spindle family, Celastraceae.  You may recognize some similarities with the related species from East Asia, burning bush  (Euonymus alatus), which is commonly planted for its bright red fall color (around Cathedral of Learning in Pittsburgh, and many other places).  However, burning bush should not be planted, as it is invasive, spreading into natural areas.
 
In the Carnegie Museum herbarium, there are 62 specimens collected by Darlington between 1828 and 1840, mostly from Chester County, PA. 
 
How’d some of Darlington’s specimens end up at the Carnegie Museum?  This specimen was part of Jacob Wolle’s personal collection, who was the grandfather of William Holland, the first director of the museum.
 
This specimen image is now publicly available online: http://midatlanticherbaria.org/portal/collections/individual/index.php?occid=12131484&clid=0
 
Read more about  Darlington and other influential figures in the history of Pennsylvania botany at Herbarium World: https://herbariumworld.wordpress.com/2017/07/10/william-darlington-and-the-pennsylvanica-botanical-circle/

Watch out for poison ivy!  Both because it is a fascinatingly cool plant but also a potentially dangerous one. 

This flowering specimen of poison ivy was collected on May 31, 1903 by John Shafer (first curator of botany at Carnegie Museum) and O.P. Medsger in the Laurel Highlands of southwestern PA.
 
Poison ivy (Toxicodendron radicans) is a woody vine found in forest understories, but does especially well on forest edges. It is very common in urban and suburban environments. It takes many forms, climbing high up a tree, along the ground, or even a short shrubby thing. The leaves take a range of shapes, but as the adage goes (“leaves of 3, let it be”), it has three leaflets.
 
Poison ivy is known by many for its chemistry, producing a class of organic compounds call urushiol found in the plant’s sap and on leaves/stems/roots that cause a nasty rash to those who touch it. Not all people have a reaction (but most are sensitive), but don’t be too confident - it can develop with repeated exposure.  Incredibly itchy, the rash can become a serious health issue if infected, and especially if it oils get in contact with your eyes, face, or throat.  The rash can appear days after exposure and can last for weeks.
 
Research indicates poison ivy will get more poisonous with climate change, both in terms of growth and producing higher quantities of forms of urushiol particularly toxic to humans.
 
It is often considered a “weed” because of its fear-causing rash, but it is native to eastern North America.  The species has a wide distribution across our region, and across the world (native subspecies in China). Although native, the species seems to be getting more common as we create more forest edge habitat.   The colorful foliage can be quite beautiful in the fall, and the berries are a food source for birds and other animals. Humans seem to be the only ones allergic to it.
 
Poison ivy is often confused with other non-poisonous and poisonous plants. Some common confusions are 1) Virginia creeper (Parthenocissus quinquefolia), a vine in the grape but different leaves, and not with leaves of three and 2) Box elder maple (Acer negundo), a tree that has compound leaves unlike most stereotypical maples,  but with samaras (aka “helicopter” seeds).  
 
Poison ivy and some other rash-causing plants are in the cashew family (Anacardiaceae) – which also includes poison oak (not found in Pennsylvania, but in western USA), staghorn sumac (not rash causing), poison sumac (rash causing, but you likely won’t come across it unless in very wet habitats)....and even a few familiar species like  pistachio,  cashew, and mango (some people are allergic).  
 
What an amazing plant. 

This specimen image is now publicly available online: http://midatlanticherbaria.org/portal/collections/individual/index.php?occid=12232529&clid=0

In July 2017, I collected poison ivy, and was not careful.  Poison ivy rash on  your finger  tips is an awful experience.  This picture was from weeks after.

Collected 67 years ago, the specimen on the left of creeping phlox  (Phlox stolonifera) was collected by past Carnegie Museum curator Leroy Henry and Werner Buker, a long time museum volunteer and prolific plant collector.

Fast forward 65 years, the specimen on the right is of the same  species and collected in the same location in Somerset  County, Pennsylvania by Mason Heberling (me!) and Bonnie Isaac, collection manager. 

This specimen is part of a long-term recollection plan at the museum, where we are going back to sites across western PA on the same day as other botanists, decades or often a century  later, to document change through time.  By revisiting sites, we are able to  compare what is there that is still there, what was there that isn't there anymore, and what is there that wasn't there before (such as introduced species)!  And within  species, we are able to compare timing of flowering, plant size, etc.  

Many more (re)collections to come!

This four-leaf clover was collected by our very own mollusk curator Tim Pearce on July 5, 2014 in Pittsburgh. Tim must be a lucky person, having found several other four-leaf clover specimens and now in the Carnegie Museum Herbarium. This particular specimen is white clover (Trifolium repens), a species native to Europe but common in lawns worldwide. Many clovers have three leaflets (hence the genus name “tri” – “folium”), but according to folklore, those uncommon plants with four leaves bring luck.
 
This lucky specimen was imaged recently (along with many others in the clover family, Fabaceae) and is publicly available online: http://midatlanticherbaria.org/portal/collections/individual/index.php?occid=21236224&clid=0
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What’s a shamrock? There is no overwhelming scientific consensus on which species is the well-known Irish national emblem.  There was survey of Irish botanists in the early 1890s asking which species was the “true” shamrock.  A similar survey was repeated in 1988.  The results suggest the shamrock is either Trifolium dubium (aka “lesser trefoil”) or Trifolium repens (aka “white clover”).  The plants commonly sold around St. Patrick’s Day as “shamrocks” or “4-leaf clovers” are in the plant genus Oxalis (“wood sorrel”), which belong to different plant family than true clovers.
 
Top left: Trifolium repens (collected 1974 in Louisiana), aka “white clover”
Top right: Trifolium  dubium (collected 1961 in Pennsylvania), aka “lesser trefoil”
Bottom left: Oxalis tetraphylla (collected 1981 in India), aka “lucky clover,” although not a true clover
Bottom right: Oxalis debilis (collected 1989 in cultivation), aka “pink woodsorrel”
 
These specimens were recently imaged (along with many others in the legume family, Fabaceae) and are publicly available online: http://midatlanticherbaria.org/portal/collections/list.php?db=328&hasimages=1&includecult=1&taxa=trifolium&usethes=1&taxontype=2
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Don’t touch that! This leafless specimen of poison ivy (Toxicodendron radicans) was collected by C.H. Morgan on March 11, 1922 near Port Vue (near McKeesport just outside of Pittsburgh). Although best admired from a distance, poison ivy is a remarkable plant.  And like it  or not, a plant that has become a part of our urban landscape.  The leaves can be spectacularly red colored in the fall with beautiful berries. But still, do not touch. Not all of us are allergic to poison ivy, but even if you don’t think you are, you can become sensitive to it in time.  (From experience, getting the rash on your fingertips is not fun at all...)
 
All parts of this species are considered poisonous, containing the group of chemicals causing that nasty rash in humans, urushiol. Only humans are susceptible to the rash, as poison ivy is eaten by other animals. Getting it on your skin can be painful. The oils can also be inhaled (when burning wood) and cause serious respiratory illness or damage to eyes.
 
This particular specimen may not have leaves like most herbarium specimens, but check out the impressive aerial roots on the left. Poison ivy is a trailing or climbing vine (or even shrub) that can be quite diverse in terms of leaf shape and growth habit. In addition to its distinctive leaves of three, climbing plants have noticeable aerial roots, adhering the vine to the bark of host tree.
 
Why does poison ivy produce urushiol?  The answer is not totally clear, but probably not to deter humans, but instead as an antimicrobial agent.
 
Note the specimen label reads “Rhus toxicodendron.”  Although  the species is related to sumac (which are in the genus Rhus), poison ivy is now recognized in a separate genus, Toxicodendron, which means “poison tree.”
 
Poison ivy is native to North America. The species in the cashew plant family (Anacardiaceae), which includes several other species which produce skin irritants. In addition to poison ivy, poison oak, and poison sumac, the family also includes mango and cashew.  Interestingly, the shell of the cashew nut contains chemicals that can cause similar allergic skin reactions as poison ivy.
 
Research indicates that poison ivy may be doing better in a warming world, both in terms of growth and producing higher quantities of forms of urushiol particularly toxic to humans. Poison ivy also  tends to do well in disturbed environments, such as urban areas.
 
This specimen image (and all other poison ivy specimens in the region) are available online: http://midatlanticherbaria.org/portal/collections/individual/index.php?occid=12232543&clid=0

Do you think Punxsutawney Phil was ever overcome by the beauty of this very violet 71 years ago? 

Or perhaps he nibbled off a leaf or two? 

After all, legend has it that Phil is over 100 years old! This specimen of Labrador violet (Viola labradorica) was collected near Phil’s home in Punxsutawney , Pennsylvania on June 2, 1948 by Carnegie Museum botany curator Leroy Henry.
 
In case you wondered, on Groundhog Day 1948, Punxsutawney Phil saw his shadow and predicted six more weeks of winter.
 
This specimen was imaged recently (along with many others in the violet family) and is publicly available online: http://midatlanticherbaria.org/portal/collections/individual/index.php?occid=11964316&clid=0

 Collected on this Day in 1927
 
Well, collected on this month.  Maybe this day, who knows? 

The distinctively hairy twigs with large bud scars of staghorn sumac (Rhus typhina) collected in January 1927 by Amy Neale in “dry soil” in Kittanning, Pennsylvania (Armstrong Co).  I’m not sure what motivated this collection or unfortunately, much about Amy Neale.  The Carnegie Museum herbarium has 261 specimens collected by Amy Neale, all near or in Kittanning, PA.  
 
You can  see these collections here: http://midatlanticherbaria.org/portal/collections/list.php?db=328&collector=neale&page=1
 
All of these specimens will be imaged in the next two years.
 
Staghorn sumac is an early successional small tree that is native to PA and often grows in clusters along highways, old fields, and other open habitats. Its twigs and fruit are distinctive, especially in winter --- a classic part of the Pennsylvania landscape in my opinion! It is often viewed as a “weed” or “junk tree” with cheap, fast growing stems.  But it is an incredible plant.
 
I’m always intrigued by specimens of twigs collected in winter.  There are several collectors in Western Pennsylvania who collected dozens to hundreds of such specimens.
 
This specimen image is now publicly available online: http://midatlanticherbaria.org/portal/collections/individual/index.php?occid=12232636&clid=0


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Check back for more! Botanists at the Carnegie Museum of Natural History share digital specimens from the herbarium on dates they were collected. They have embarked on 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. ​