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.
Nancy Hanks Lincoln (mother of Abraham Lincoln) died on Oct. 5, 1818 from “milk sickness.” Milk sickness is caused by poisoning after drinking milk from cows that have eaten the plant white snakeroot (Ageratina altissima). Also known as “puking fever” or simply “the trembles,” early European-American settlers in the Midwest initially thought milk sickness was an infectious disease. It was soon realized that the unidentified illnesses were caused by drinking milk from cows that ate white snakeroot, which contains the chemical tremetol, a toxin which causes weakness, pain, vomiting, abdominal pain, and can lead to coma and death. The cattle of these early settlers often wandered into the forest to graze, seeking additional forage outside limited pastures. However, milk sickness is very uncommon today due to modern farming practices and cows rarely have access to eat this plant.
White snakeroot is a fall blooming, shade-tolerant species found in forests across the Eastern US, and commonly found throughout southwestern PA. This specimen pictured was collected in 1998 in southwestern Indiana, about 90 miles north of the Little Pigeon Creek Community, where Abraham Lincoln’s family lived.
white snakeroot at Trillium Trail, Fox Chapel Borough, PA (Allegheny Co.); Sept. 19, 2016
Giant hogweed (Heracleum mantegazzianum) is considered a significant public human health concern. This non-woody plant can be 8-20 feet tall with leaves up to 5 feet wide! In fact, it took 6 separate herbarium sheets to capture the characteristics of this species. This specimen was collected from a garden, where it was intentionally grown for the purposes of educating the public about this plant. Native to central and southwest Asia, this plant can now be found in parts of Europe, Australia, New Zealand, and North America. It is thought to be eradicated in Pennsylvania.
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 is also said to cause blindness.
Giant hogweed, like poison hemlock and Queen Anne’s lace, is in the carrot family (Apiaceae). It might be confused with the related native plant, cow parsnip (Heracleum lanatum), but giant hogweed is noticeably larger in height and flower size.
Collected on June 23, 1993, this specimen was found by Fred Utech near the Loyalhanna Creek in Salem Township, PA.
Don’t let the “weed” in common name affect your opinion of this plant! Butterfly weed (Aclepias tuberosa) is a beautiful plant and the pollinators love the bright orange flowers. Native to eastern North America, it can be found in dry, full sun conditions. It is a great plant to add to your garden!
Like other milkweeds (butterfly weed is in the milkweed genus), butterfly weed flower clusters mature into seed pods which eventual dry up to release airborne seeds in the late summer. The long silk-like hairs (called pappi, or singular: pappus) have been used by native Americans to make textiles.
Despite its looks, butterfly weed is poisonous to ingest. Like other milkweeds, this plant contains defensive chemicals called cardiac glycosides, which are poisonous to humans, livestock, and pets. Milkweeds vary in their toxicity depending on species and age of plant. Symptoms can include: weakness, difficulty breathing, kidney damage, cardiac distress, pupil dilation, loss of muscle control, and respiratory paralysis.
Butterfly weed flowers open early- to mid-summer (above).
Seeds burst from pods and blow in the wind in late summer (below).
Collected on June 16, 1925, this specimen was found near Shinglehouse, Potter County, PA by H.W. Graham.
Poison ivy (Toxicodendron radicans) is a species you might be very familiar with! Poison ivy is a native woody vine found in wooded areas, along paths, and edges of woods across the eastern United States.
the species can take various forms and habits, growing as a vine along the ground, up a tree, or as a small shrub.
Poison ivy is famous for a chemical it produces, urushiol, which upon contact, can cause a severe skin rash in humans. The rash, which can last up to several weeks, can also lead to an infection due to intense scratching that breaks the skin. Serious health effects can stem from ingesting urushiol or can cause other allergic reactions in eyes and throat when inhaling smoke from burned plants. If you come into contact with poison ivy, the best way to prevent an allergic reaction is washing with water and soap (or other detergent to wash off oils) as soon as possible. Some people are more sensitive to poison ivy than others, or become more sensitive after repeated exposure.
Poison ivy is 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.
You might have heard “Leaves of three, let it be,” but what does that mean exactly? And how do you know if it is poison ivy, poison oak, or poison sumac? Many plants might at first glance resemble poison ivy, but they can be easily distinguished. Poison ivy is common in woods, forest edges, roadsides, and weedy areas throughout Pennsylvania, and has aerial, hairy-looking rootlets on stems of vines. Poison sumac (Toxicodendron vernix) is also native to Pennsylvania, but is less common and only found in swamps and other persistently wet habitats. Poison sumac (Toxicodendron vernix) has leaves made up of many more leaflets than poison ivy. Lastly, poison oak (Toxicodendron diversilobum) is sometimes confused with poison ivy, but it is unlikely you encountered this species in Pennsylvania -- it is only native to the western United States.
Left: Poison ivy (Toxicodendron radicans), common in woods, trails, and forest edges in PA
Middle: Poison oak (Toxicodendron diversilobum), you might be out West
Right: Poison sumac (Toxicodendron vernix), you might be in a swamp
Collected on June 9, 1959, this specimen was in the woods along a road to Pocahontas, near Salisbury in Somerset County, PA by Leroy Henry. Henry was the Curator of Botany at the museum.
Mountain laurel (Kalmia latifolia) is the state flower of Pennsylvania! It is a broadleaved evergreen shrub native across the eastern US, especially in forests of mountainous areas. This specimen was collected not too far from the highest point in Pennsylvania and the Maryland border. Often mistaken for Rhododendron, both the Rhododenrons and mountain laurel are found in similar habitats and belong to the heath family (Ericaceae).
Despite its beauty, mountain laurel has a dark side: all parts contain toxins that are poisonous to humans, pets, horses, and cattle. Ingesting this plant can cause vomiting, diarrhea, impaired vision, convulsion, cardiovascular distress and death. Honey made by bees from mountain laurel can also cause medical problems to humans. Benjamin Smith Barton (American botanist in late 1700s) wrote that “in the autumn and winter of the year 1790, many people died in Pennsylvania from the effects of wild honey, collected from Kalmia plants.”