HEBERLING LAB

Spring at Powdermill.
An early bloomer.
 
This specimen of coltsfoot (Tussilago farfara) was collected at Powdermill Nature Reserve, the field station of Carnegie Museum of Natural History in 1957, just one year after Powdermill was established. It was collected by Leroy Henry, a curator of botany at the museum from 1937 until 1972 (though was also affiliated with museum before and after that, too!).  Henry is an important collector for our region, with >36,000 specimens in the Carnegie Museum herbarium.
 
At first look, the plant may be confused with your common dandelion.  It has definite similarities, as it is in the same plant family, Asteraceae, and with yellow flowers.  But, as you’ll notice from the specimen – it doesn’t have leaves!
 
Coltsfoot is introduced to Pennsylvania, native to Europe, and quite unique in our flora.  It blooms very early in the spring, with dandelion-like flowers poking through.  The leaves will soon follow, shaped like – well – a colt’s foot!  Quite different than dandelion. 
 
Its blooming also makes it a great species to track changes in bloom time using herbarium specimens.  The species was among the first to be use in a pioneering study published in 2006 using herbarium specimens by Claud Lavoie and Daniel Lachance.  In Southern Quebec, they found coltsfoot bloomed 15-31 days earlier in recent decades, compared to pre-1950. Earlier blooming was strongly linked to climate change in the region.  The plants also showed a clear signal of flowering earlier in the city (due to urban heat island).
 
We have plenty of spring ephemerals that bloom early, but coltsfoot doesn’t die off by summer.  The plant will keep its leaves well after it blooms, into late fall.
 
This strategy is interesting, and I can’t think of many of plants in our flora that does this.  Is it on to something?
 
Keep an eye out for coltsfoot, especially along wooded roadsides.  Once you see a big bloom, check back later in the year.  The leaves can get quite large.
 
Find this specimen and more here: https://midatlanticherbaria.org/portal/collections/list.php?db=all&catnum=CM092465&includeothercatnum=1
 

Spring is springing as we speak
in the city and beyond.
 
This specimen of common chickweed (Stellaria media) was collected on the campus of Carnegie Mellon University in Pittsburgh in a “mostly shady area.”  Though small, if you look closely you are met with a charismatic tiny flower.  Common chickweed is incredibly common across the world, found in every continent (except perhaps Antarctica?).  Like many cosmopolitan lawn weeds, it is native to “Eurasia” and its exact native range is unclear.  But it is considered not native to North America.
 
Common chickweed can be found from an urban lawn to a forest in Pennsylvania.  The plants can form a mat along the ground.  They can be found just about year round when snow isn’t on the ground, and like dandelion, flowers throughout the year.
 
But the flowers now are also telling – spring is on the way.  For some plants, such as skunk cabbage and red maple, spring has already sprung.
 
This species is a good one to look out for during the upcoming City Nature Challenge!
 
Find this specimen and more here: https://midatlanticherbaria.org/portal/collections/list.php?db=all&catnum=CM540683&includeothercatnum=1

Honeysuckles will be back soon. 
But this one never really left for the winter.
 
This specimen of winter honeysuckle (Lonicera fragrantissima) was collected in West Conshohocken, PA near the Schuylkill River outside of Philadelphia by Bayard Long.  Collected flowering in a “rubbish-dump,” no less! Bayard Long (1885-1969) was a Philadelphia-area botanist and an active member of the Philadelphia Botanical Club (founded in 1891 and still exists today).  He was a prolific collector and served as Curator of the Club’s Local Herbarium for 56 years (housed at the Academy of Natural Sciences). About 982 specimens collected by Long are preserved for the long haul in the Carnegie Museum herbarium.
 
Winter honeysuckle not only has a fun scientific name to say (“fragrantissima” rolls off the tongue) but is easy to identify among the many species in the honeysuckle genus (Lonicera in plant family Caprifoliaceae).  That is, it has almost evergreen (or in Pennsylvania, almost evergreen), thick leaves that partly persist into the winter, unlike any of the other shrub honeysuckles in Pennsylvania.  (Emphasis on shrub, because the invasive vine Japanese honeysuckle – Lonicera japonica- also has persistent leaves through much or all of winter).
 
It is also known as “sweet breath of spring” for its aromatic flowers (hence its specific epithet, fragrantissima – think Bath and Body Works scent), which appear in late winter (and in this specimen!).
 
Introduced from China as an ornamental and often planted for its foliage, this species is now invasive in many states in the US.  I must admit I don’t see it very often “escaped” outside of plantings in Western PA, but that doesn’t mean it doesn’t exist, or won’t escape in time, especially given it is problematic in other areas of the US.
 
So, you really shouldn’t plant it.  Though Pennsylvania has native honeysuckles, the most abundant and common ones are introduced, affecting native vegetation and wildlife.
 
Find this specimen (and search for more) here: https://midatlanticherbaria.org/portal/collections/list.php?db=328&catnum=CM302294&includeothercatnum=1
 

Not yet blooming here, but it likely is in the Mediterranean.
 
This specimen of lesser celandine (Ficaria verna formerly known as Ranunculus ficaria, in the buttercup family, Ranunculaceae) was collected in January 1911 by Mary F. Spencer in Corsica.  A part of France, Corsica is an island in the Mediterranean.  This specimen was collected in its native range, which extends from Europe to west Asia.
 
Lesser celandine is quite remarkable, one of the earliest blooming spring wildflowers. It isn’t blooming in the Pittsburgh region yet, but can be as early as March.  It was introduced to North America and is actively spreading throughout forest understories in Western PA and beyond, especially along streams and floodplains.
 
Lesser celandine is a problematic invasive species. And only likely to become more of a problem as it actively spreads across the landscape.  It is unique among invasive species, perhaps the only with a “spring ephemeral” ecological strategy.  Spring ephemerals produce leaves and flowers very early in the spring and dies back before the overstory trees produce leaves.  It forms dense mats along the forest floor, crowding out our native spring wildflowers.
 
It was introduced intentionally as a garden plant, producing glossy, yellow flowers which can be quite beautiful.  But it should not be planted, as it negatively impacts our forests and can easily spread outside gardens into natural areas.
 
Keep an eye out for this species in Pennsylvania!  I have been noticing it more each year. 
 
Find this lesser celandine species here:  https://midatlanticherbaria.org/portal/collections/individual/index.php?occid=12087827
 

Lesser celandine (Ficaria verna​) invasion in Fox Chapel, Pennsylvania.  The species can form dense mats on the forest floor, emerging in early spring in a spectacular display of flowers.  But it is very invasive, crowding out native species.  As a spring ephemeral, the species takes advantage of the high light levels in the spring and completes its aboveground life cycle before being shaded out by the trees overhead.

Has your Charlie Brown tree lost its needles yet?
 
Not all needled-leaved trees are evergreen! Yes, there are deciduous species in the Pine family (Pinaceae).  That is, unlike most needle-leaved trees that retain their leaves all year long (evergreen), there are several conifer species that shed their leaves each year for the winter. Perhaps most famous are a group of species called larches.
 
No, this needle-free specimen of twigs and a cone wasn’t collected by Charlie Brown on Christmas Eve. Rather, this humble yet festive specimen of European larch (Larix decidua) was collected by J.F. Lewis on December 24, 1934.  Native to the mountains of central Europe, this species was planted in a cemetery in Northumberland county (central Pennsylvania).  It is highly likely the tree is still there – many decades later – as European larches can live for many hundreds of years (perhaps even a thousand years!). 
 
The herbarium at California University of Pennsylvania is named the person who collected this specimen – John Franklin Lewis.
 
European larch recently made the big time news too, featured in a new study published in the scientific journal Science.  The researchers used leaf out and leaf fall data collected from across Europe since the late 1940s for four tree species (including European larch). Surprisingly they found that trees may drop their leaves much earlier than expected with ongoing climate change.  In other words, as spring temperatures warm, deciduous trees produce leaves earlier in the spring, but this also causes trees to drop their leaves earlier in the fall.  This means that climate change may not result in longer growing seasons, as has been previously predicted.  You can read more about this study here: https://crowtherlab.pageflow.io/phenology-autumn-senescence#276245
 
 
Find this Charlie Brown larch specimen (and more) here: https://midatlanticherbaria.org/portal/collections/list.php?db=all&catnum=CM228058&includeothercatnum=1

Autumn has fallen. (Fall has autumned?)
 
This specimen of red maple (Acer rubrum) was collected on November 13, 1915 by Otto Jennings near Finleyville, Pennsylvania (about 30 miles south of Pittsburgh).  Jennings was an influential botany curator (and biology professor at University of Pittsburgh and director of Carnegie Museum, among many other roles through his many decades career at the museum).
 
Just imagine how beautifully red these leaves must have been.   And you’ll have to imagine because this specimen is just twigs!
 
But upon closer look, the twigs have a lot to admire.  As with other deciduous trees in Pennsylvania, the buds are primed and ready.  In spring (as early as March for red maple!), these buds will swell and flowers will emerge.  Leaves will follow.  
 
But first, we wait it out through winter.  
 
Pay attention to tree buds this winter. They have a lot to say.
 
Find this red maple specimen here (along with 512 others!): https://midatlanticherbaria.org/portal/collections/list.php?db=328&taxa=acer+rubrum&usethes=1&taxontype=2

Chestnuts (used to be) on Chestnut Ridge
And across the entire state of Pennsylvania.
 
American chestnut (Castanea dentata) was once a very common tree, native from Maine to Mississippi. In the heart of the Appalachians, the historical range covered the entire state of Pennsylvania. I say “historical” and “was once” because it is no longer.  You may occasionally stumble upon an American chestnut tree, especially small trees and saplings persisting as sprouts from the large trees that graced our landscape a century ago. Older trees, with mature fruits, are quite rare. 
 
In fact, some estimates suggest American chestnut accounted for one in four trees in some forests!  So, what happened?  In the early 1900s, a disease caused by a pathogenic fungus (Cryphonectria parasitica) was accidentally introduced with imported Asian trees. It was first recorded in New York City in 1904.  In a matter of decades, American chestnut was nearly decimated by this disease known as Chestnut blight.
 
The Carnegie Museum herbarium captures this change in our forests. 
 
This specimen of American chestnut was collected by influential Carnegie Museum curator Otto Jennings on October 21, 1922 on a field trip of the Botanical Society of Western Pennsylvania to Chestnut Ridge, near Derry Township, Pennsylvania.  Chestnut Ridge is a ridge of the Allegheny Mountains, presumably named for its (once) many American chestnuts. 
 
This specimen is from the fruit collection of the herbarium.  These specimens are different than the “standard” pressed flat specimens on paper.  Instead, they are stored to maintain their three-dimensional structure.
 
Note the note made by Jennings on the label on this specimen:
“Trees from ¼ to all killed by blight.”
 
The case of the American chestnut is an interesting one.  It served important cultural and ecological roles; some even calling a “keystone” species.  There is no doubt that the functional extinction of American chestnut ricocheted through the ecosystem, causing long-term biological changes. Many of these changes we may not know.  Yet, at the same time, despite the species importance, our forests continue.  Presumably other species have filled the functional and physical space of American chestnut. 
 
Disease and pest outbreaks in Pennsylvania’s forests continue.  Many of our critical tree species are likely to decline in coming years and decades.  Some iconic species have already declined or at risk.  These include our ash species (mortality caused by introduced Emerald Ash Borer), American beech (Beech leaf disease, Beech bark disease caused by an introduced scale insect), and eastern hemlock (mortality caused by introduced sap sucking bug, the hemlock woolly adelgid)...to name only a few threats.
 
What will Penn’s woods look like in another 100 years? 
Our collections document the past and present to inform our decisions for the future.

Fall blooms rival those of spring
 
In the northeastern United States, we often think of spring as a time for wildflowers.  But the fall is, too.  
 
It is easy to be distracted by the beautiful fall foliage, when our landscape turns brilliant shades of red, orange, and yellow.  But when many plants are shutting down for the winter, others are just kicking into gear.
 
Many wildflower species bloom well into fall, both in open areas and in the forest understory.  One group of plants are the fall blooming “asters.”  In same plant family as sunflowers and dandelions (Asteraceae), Aster was once a very large plant genus in our native North American flora (somewhere along the lines of >175 species!), but as we learned more about the evolutionary relationships of these plants, they have since been split into multiple genera (plural of genus). In fact, there is only one “true” Aster in Pennsylvania, Tatarian aster (Aster tataricus), which is actually not even native to Pennsylvania!  Regardless of the scientific name, these plants are commonly referred to as asters.  And they put on quite an autumn show in Pennsylvania.
 
Perhaps one of the most common woodland asters in Pennsylvania is white wood aster (Eurybia divaricata, formerly known as Aster divaricatus).  This specimen was collected in September 29, 1967 by N.R. Farnsworth in Pittsburgh’s Schenley Park.  This species can still be found in Schenley Park, and many parks, woodlands, and wooded roadsides across Eastern North America.
 
Fall foliage is beautiful in Pennsylvania.  But don’t forget to look down at the flowers, too!
 
Find this white wood aster specimen here: https://midatlanticherbaria.org/portal/collections/individual/index.php?occid=11826562

Check out the “santa claus” pappus on this specimen of bull thistle (Cirsium vulgare), collected on July 26, 1966 by Leroy Henry near Woodbine (Butler county), Pennsylvania.  Leroy Henry was a botany curator at the Carnegie Museum.  All species in the genus Cirsium are known as “thistles.”  They have distinctive spiny leaves and stems, with even more distinctive purple flower heads. There are native thistles, but many are introduced, common in disturbed areas and in and around agricultural fields across the country.  Bull thistle is native in Europe and Western Asia, but widely introduced across the world, including North America.  It is considered invasive in many areas.  It is the national flower of Scotland.
 
Keep an eye out for thistles, and “santa clauses.”  Don’t forget to make a wish.
 
Find this bull thistle specimens here: http://midatlanticherbaria.org/portal/collections/individual/index.php?occid=11831581&clid=0
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It can’t be snow, right? It’s summer!  Maybe that is cotton falling from the sky?  Well, kind of!  It is cottonwood seeds! 
 
Perhaps you’ve seen little cotton-like white particles falling from the sky in early summer, especially around Pennsylvania’s rivers or lakes. It is a common site along the dunes of Presque Isle, for example, and in areas along southwestern PA’s rivers.  Aptly named, Eastern cottonwood (Populus deltoides) is a native tree found across the eastern United States that produce seeds that fall from high up in the canopy, attached to cotton-like strands.  These help spread the seeds farther, transporting the seeds in the breeze.
 
This specimen of Eastern cottonwood was collected by Henry T. Skinner on June 8, 1942 on the sand dunes of Presque Isle, Erie. You might notice this specimen is not from the Carnegie Museum herbarium like most of these pots. But instead, this specimen is  held at the Morris Arboretum (part of the University of Pennsylvania). Now that museum collections are being digitized, we can search for species of interest, or plants collected from certain places or by certain people, or more... that’s the power of specimen digitization.  The Mid-Atlantic Megalopolis Project, funded by the National Science Foundation, is digitizing nearly a million specimens across our region,  including Carnegie  Museum specimens.  This makes our collections all the more powerful, combining all specimens collected in the region and making them accessible to scientists and the public alike.
 
Find this and more Eastern cottonwood specimens from Presque Isle here: http://midatlanticherbaria.org/portal/collections/list.php?db=all&county=erie&local=presque&taxa=Populus+deltoides&usethes=1&taxontype=2
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