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.
Does this heart-shaped leaf look familiar? 22 years ago, this specimen of heartleaf philodendron (Philodendron hederaceum) was collected on Valentine’s Day in Peru. Almost certainly you have seen this species, but probably not in the wild. Heart leaf philodendron is a very popular houseplant. This huge leaf on this specimen may look a bit different than those in your home, as the species rarely reaches maturity as a houseplant. Philodendrons have both juvenile and adult forms of their leaves, changing their form and size as they climb up a tree.
The name Philodendron comes from the Greek philo meaning “love” and dendron meaning “tree.” The name doesn’t refer to the heart shaped leaves, but rather to its growth habit as a vine that climbs trees. It is native to tropical Mexico, the Caribbean, and regions in South America.
Happy Valentine’s Day from this loving plant!
Philodendron thriving in its anthropogenic habitat in my kitchen. Philodendrons are incredibly popular as indoor plants, being easy to take care of and incredibly tolerant of low light conditions in your house. Philodendrons are toxic to pets. However, the NASA Clean Air Study has found philodendrons to improve indoor air quality.
Heartleaf philodendron at Phipps Conservatory, Pittsburgh, PA. Feb 3, 2018.
Image above: European mistletoe specimen collected on Christmas Eve, 1883.
Image below: Close up image of specimen label that reads: "a. purchased at Pittsburg market." It took me a while to decipher this handwriting. Note that Pittsburgh's official spelling was "Pittsburg" until 1911. The mistletoe was for sale for the holidays, likely imported from its native range in England.
Well, specimens don’t get much more festive than this! This mistletoe specimen (Viscum album) was purchased at a Pittsburgh market on Christmas Eve 1883 by John A. Shafer, who would become the museum’s first botany curator 16 years later. Mistletoes refer to many species in the genus Viscum, but traditionally referred to a species native to Europe, Viscum album. European mistletoe has a deep rooted cultural history, dating back to as early as ancient Greece, is a part of many legends and stories through human history, and remains a well-known holiday decoration today.
Did you know that mistletoes are parasitic plants? Mistletoes grow on the branches of trees (especially oaks), with specialized roots (called “haustorium”) that penetrate the host tree to obtain water and nutrients. Technically, most mistletoes are hemi-parasites, as they do have green leaves capable of photosynthesizing to some degree. How do they germinate high up on the branches of trees? They have evolved to produce berries which birds ingest, fly around, land on another branch, and poop a viable mistletoe seeds. Without the assistance of birds, the seeds would likely just fall to the ground.
Mistletoes are native to the United States, too. American mistletoe (Phoradendron leucarpum) is native to southeastern US states. The species has been harvested and sold in the US in Christmas traditions, similar to European mistletoe. The specimen pictured below was collected in South Carolina in 1968, found attached to several oak species.
Fa la la la la, la la la la
'Tis the season to be jolly.
Are you decking your halls with boughs of holly? This specimen of American holly (Ilex opaca) was collected by M.L. Bomhard in Mandeville, Louisiana by on December 8, 1928. The holly revered for its holiday cheer usually refers to a related European species, Ilex aquifolium. But there are native holly species in North America that are equally (if not more) cheerful. Like most other hollies, American holly is dioecious, meaning it has male and female flowers on separate plants. Only the female plants have the characteristic bright red berries we all know and love. American holly stands out as one of the few broadleaved evergreen trees native to the Eastern US (i.e., has green leaves during winter that are not needles). This species is near the northern edge of its range in Pennsylvania and is more common in southern states. It is listed in PA as a species of “special concern” due to its relative rarity.
Indiana, PA: Christmas Tree Capital of the World!
Around 25-30 million cut trees are sold each year in the United States for the holidays.
These Pennsylvania specimens shown above were collected sometime in December (exact day unknown): White Pine (Pinus strobus) in Kittanning in 1926 and Scots Pine (or “Scotch Pine”; Pinus sylvestris) from cultivation in Avalon in 1902. Both of these species are cultivated and used as decorative trees for the holidays. Many evergreen conifer species are cultivated in the US for decorative use during the holidays. Needle length, softness, retention, color, and even scent vary by species or variety. Similarly, branching patterns and branch strength differs. Plus, some species grow faster and easier than others, which means some species are cheaper.
Did you know that Pennsylvania is one of the top states for Christmas tree farms? In fact, southwestern PA’s very own Indiana County is known as the “Christmas Tree Capital of the World.” According to the Indiana County Christmas Tree Growers’ Association, the title arose in 1956, when an estimated 700,000 trees were cut that year in the county.
Believe it or not, there are no CM specimens from Indiana County collected in the month of December. This isn't all that surprising, as most specimens aren't collected in the winter.
Before farms began cultivating trees for that purpose in the early 20th century, people just went to the woods to cut down their tree for the holidays. Some of the earliest Christmas tree farms in the US started in Indiana County as early as 1918. Many farms in the region turned their fields into Christmas tree farms as it became profitable. By 1960, more than 1 million trees were harvested per year in Indiana County alone. The harvest in Pennsylvania has declined for several reasons, including increased popularity of artificial trees and consumer interest in Frasier fir trees (Abies fraseri; native to the Southern Appalachians and grows slower in PA than farms in North Carolina). However, Pennsylvania is still among the top five states in terms of both number of working Christmas tree farms and trees harvested. According to the National Christmas Tree Association, 31,577 acres in Pennsylvania are used as Christmas tree plantations. Many of the Christmas tree lots in southwestern PA get their trees from farms in Indiana county.
What you know as yams are most likely not really yams. In fact, your “classic” potatoes, sweet potatoes, and yams are all in different plant families. However, they all are widely cultivated for their nutritious starchy belowground plant structures called “tubers.” Tubers function as storage organs for the plants, providing energy for regrowth (the “eyes” or sprouting buds of your potatoes when they sit in your kitchen for too long). Potatoes and yams technically have modified belowground stems (“stem tubers”) while sweet potatoes have “root tubers.”
Yam is a common name for several vine species in the genus Dioscorea (plant family: Dioscoreaceae). They are monocots (related to grasses and lilies). Yams are widely cultivated worldwide, especially in West Africa, where 95% of the crop is harvested. Yams can be stored for very long periods of time, making them an important crop for seasons when food is in short supply. Yam tubers can be as large as five feet long!
Sweet potatoes refer to a vine species (Ipomoea batatas) in the morning glory family (Convolvulaceae). This species is likely what is on your Thanksgiving dinner table. In the United States and Canada, sweet potatoes are often (confusingly) referred to as “yams.” But sweet potatoes are not even closely related to yams. As such, the USDA requires any label with “yam” to also include “sweet potato.” So why are sweet potatoes sometimes confusingly called yams?! Well, this naming probably dates back to colonial times when slaves from Africa noted the similarities between some varieties of sweet potatoes to yams in Africa.
And last - the “classic” potato, Solanum tuberosum. Potatoes belong to the nightshade family (Solanaceace), which also includes many other important crops like peppers, tomatoes, tomatillos, eggplant, tobacco, and more. Critical to the world’s food supply, potatoes are the fourth most farmed crop. Potatoes are only distantly related to sweet potatoes. They are also called “spuds,” which probably originated centuries ago from a term for a spade used to dig holes to plant potatoes. Having been cultivated for centuries, there are thousands of potato varieties worldwide. The cultivated species was domesticated from wild relative potato species in South America (Peru) 7,000 – 10,000 years ago. Important discoveries on the origin of potatoes were based on DNA from 200 year old herbarium specimens! Similarly, the origin of the Irish Potato Famine (caused by potato late blight from a fungal pathogen) was also discovered using fungal DNA extracted from 160+ year old herbarium specimens!
For more on cool new Irish potato famine research: http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0168381
For more on origins of European potato: https://www.ncbi.nlm.nih.gov/pubmed/21632349
Specimen above: "Yam" species (Dioscorea schimperiana) collected in 1960 by A.C. Twomey in Kenya. Yams are an important food crop across Africa.
Specimen below: "Sweet potato" (Ipomoea batatas 'Georgia Jet') collected in 2001 by Bonnie and Joe Isaac in a garden in Pennsylvania.
Specimen below: Your "classic" potato (Solanum tuberosum) collected in 1982 from a farm in Peru. Research suggests Peru to be the site of early domestication over 7,000 years ago.
There’s a deeper evolutionary history behind jack-o-lanterns and pumpkin spice lattes than you might think. Recent research from Penn State indicates the plant lineage might have went extinct had it not been for humans. Species in the genus Cucurbita (including pumpkins, gourds, squashes) were domesticated by humans in eastern North America about 10,000 years ago. That is, they were cultivated in gardens, likely first selected for the use of their durable rinds (anthropological evidence for gourds used as containers for drinking) and later as a food source. Most Cucurbita species went extinct around this time, coinciding with the extinction of large mammals that these species relied upon to spread their seeds. Their fruits were unpalatable to the smaller herbivores that did not go extinct. Ironically, it is human hunters, paired with climate change, that led to the extinction of large herbivores in North America. Modern day pumpkins have adapted to the Anthropocene.
Collected near Freedom (Beaver county, PA), this pumpkin specimen (Cucurbita pepo) was collected from Dun’s Farm in 1884 by John A. Shafer, who became the first Curator of Botany at the Carnegie Museum of Natural History a decade later.
Collected in 1908 (the first year Mother’s Day was celebrated!), this specimen was grown in cultivation at the former western headquarters for the Ferry-Morse Seed Company in Mountain View, California. The white carnation was chosen as a Mother’s Day symbol by Anna Jarvis, the holiday’s founder, because they were her mother’s favorite. Carnations remain closely associated with Mother’s Day in the United States, with white carnations traditionally as symbols in memory of mothers who have died and colored carnations to honor living mothers. The carnation, or Dianthus caryophyllus, is probably native to the Mediterranean, but its native range is obscured by at least 2,000 years of cultivation. There are over 27,000 named cultivars of Dianthus species.
Collected in Ireland in 1891, this specimen (above) was found by Susan and Edward Harper, who were plant collectors from the Field Museum in Chicago. This specimen is a clover species (Trifolium campestre), known as hop trefoil or field clover. Clovers are a group of species that usually refers to those belonging to the genus Trifolium, meaning “three-leafed.” For next year’s post, I'll look for that mystical 4-leaf clover among the 1,877 clover specimens in the Carnegie Museum’s Herbarium.
So what exactly is 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”). But there are no official rules for common names. 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), “white clover” likely seen in your backyard
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”
Collected on February 14, 2005, this specimen was found in Costa Rica by John Paul as part of his graduate research at the University of Pittsburgh.
This species is particularly appropriate for Valentine’s Day because before it flowers, it produces deep red, petal-like leaves called bracts that resemble human lips. Psychotria elata (also known as “hot lips” or "hooker's lips") is part of an important group of plants in the coffee family, native to tropical forests across the world.