Discover the 8 Most Dangerous Plants in Pennsylvania

Wild parsnip flowering
© iStock.com/RuudMorijn

Written by Em Casalena

Updated: June 29, 2023

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Pennsylvania is home to some seriously beautiful plants, from the cardinal flower to the iconic red maple. However, Pennsylvania is also home to quite a few unique and very dangerous poisonous plants. And it’s vital to know what these plants are, as they tend to be in bloom in spring or early summer. Read on to learn more about the most dangerous plants in Pennsylvania!

The Importance of Identifying Dangerous Plants

It’s crucial to know how to recognize hazardous plants for a number of reasons. To begin with, knowing which plants are toxic can help reduce the potential for illness from accidental touch or consumption. Many toxic plants can result in symptoms as severe as skin irritation, allergic responses, digestive problems, or other conditions that may need medical treatment.

Knowing how to identify hazardous plants is essential while hiking, camping, gardening, or doing other outdoor activities. It enables people to stay away from regions where these plants are grown or to take the appropriate safety measures to avoid exposure. With all of this in mind, let’s dive into our list of dangerous plants in Pennsylvania!

1. Wild Parsnip

Classification: Pastinaca sativa

The first entry on our list of dangerous plants in Pennsylvania is a very common species. Wild parsnip is a biennial member of the Apiaceae family, sometimes referred to as the carrot family. It is an invasive species that was once only found in Europe and Asia but has now expanded to many parts of North America, including Pennsylvania. Wild parsnip can reach a height of five feet and has unusual umbels of yellow-green blooms that resemble flat-topped bouquets.

Wild parsnip grows in a variety of settings in Pennsylvania, including fields, meadows, roadside ditches, and similar areas. Due to its preference for full sunshine and well-drained soils, it is especially common near highways and in open spaces.

Although wild parsnip might seem innocuous, it really poses a serious hazard to both people and animals. A photosensitizing substance known as psoralen is present in the plant’s sap. A disease known as phytophotodermatitis can be brought on by contact with the sap and sun exposure. This illness causes painful and severe skin rashes, blisters, and burns. Usually occurring 24 to 48 hours after contact, the response may result in scarring or long-lasting reddish discoloration on the skin.

Grazing animals on wild parsnip can potentially have negative impacts. When livestock comes into contact with the plant, dermatitis can occur. Animals that consume a lot of wild parsnip may experience toxic responses that cause digestive upset and photosensitivity. To reduce the possibility of unpleasant and perhaps persistent skin responses, it is imperative that both people and animals avoid coming into contact with wild parsnip. Wearing protective clothes such as long sleeves, trousers, and gloves is strongly advised when coming into contact with wild parsnip.

Wild parsnip flowering

The sap from wild parsnip is harmful to both humans and animals.

©iStock.com/RuudMorijn

2. Creeping Thistle

Classification: Cirsium arvense

The Asteraceae family includes perennial herbaceous plants like the creeping thistle. It is an extremely invasive plant that is native to Europe and Asia and is sometimes referred to as field thistle or Canadian thistle. The sturdy, erect stem of the creeping thistle is covered in spiky, spiny leaves, and it produces clusters of pink or purple flowers.

In Pennsylvania, you can find creeping thistle in disturbed areas, pastures, meadows, roadsides, and waste areas. It can grow quickly and flourish in a variety of soil types, generating thick clumps that stifle local plants.

Due to its aggressive attitude and the presence of spines and prickles, creeping thistle poses a hazard to both people and animals. When touched, the sharp leaves and stems can irritate the skin and create small wounds. The plant forms enormous networks that are challenging to manage and remove thanks to its subterranean rhizomes, which allow it to propagate.

Additionally, creeping thistle degrades pastures and reduces agricultural yields by competing with beneficial plants for space, nutrients, and water. It may swiftly encroach upon agricultural regions, costing farmers quite a bit of money.

Creeping thistle can also harm animals, especially grazing cattle. Animals who are grazing may get wounds to their mouth, lips, or digestive systems due to the presence of prickly leaves.

It is crucial to use efficient management strategies, such as routine mowing, herbicide treatment, or hand removal, to lessen the effects of creeping thistle. Appropriate management techniques can limit its detrimental impacts on ecosystems. It just takes a little elbow grease to keep them at bay! 

Cirsium arvense or creeping thistle growing in a field with purple flowers.

Creeping thistle (pictured) can be harmful to both people and animals.

©Thorsten Schier/Shutterstock.com

3. Virginia Creeper

Classification: Parthenocissus quinquefolia

The deciduous vine known as Virginia creeper is indigenous to eastern and central North America. It is a member of the Vitaceae family and is well known for its colorful fall leaves. The characteristic palmate leaves of Virginia creeper have five leaflets and are distinctively shaped; they are green throughout the growing season and turn crimson, orange, and purple in the fall.

Virginia creeper grows in a number of environments in Pennsylvania, including disturbed areas, fence lines, forests, and forest margins. It is an active climber that clings to buildings, trees, and other vertical surfaces with the help of its tendrils. The plant can tolerate a variety of soil types but favors wet, well-drained soils.

Although Virginia creeper isn’t thought to be very harmful, it can produce moderate discomfort in some people when touched. Itching and redness may be brought on by skin rash or dermatitis that is brought on by the plant’s sap. Even though Virginia creeper berries are regarded as having minimal toxicity, eating them might cause stomach discomfort.

Additionally, Virginia creeper has the potential to spread aggressively under some conditions, particularly when it is introduced to non-native settings. It has the ability to smother and shade out other plant species because of its quick growth and climbing behavior, which may have an adverse effect on local flora and decrease biodiversity. Therefore, in locations where Virginia creeper may become invasive, it is crucial to regulate and restrict its spread.

Despite the fact that Virginia creeper has aesthetic value and is not particularly harmful, it is nevertheless important to use caution while handling the plant and to keep an eye on its development to avoid any negative impacts on local ecosystems.

virginia creeper closeup

Virginia creeper can reach up to 100 feet tall.

©iStock.com/drasa

4. Morning Glory

Classification: Ipomoea genus

This entry on our list of dangerous plants in Pennsylvania refers to a whole genus rather than just one species. Ipomoea is the official name for the genus of flowering plants known as morning glory. It is a member of the Convolvulaceae family. This broad group, which consists of annuals, perennials, and vines, is known for its colorful and ostentatious trumpet-shaped blooms that open in the morning, giving rise to the name “morning glory.” Although morning glories are commonly grown and may be seen growing in numerous areas of Pennsylvania, they are native to tropical and subtropical climates.

Morning glories flourish in sunny, well-drained areas of Pennsylvania. As a result of their natural climbing ability, they are frequently seen in gardens, along fences, and on trellises, where they may tangle and scramble their way to heights of many feet.

Despite having a beautiful appearance, the genus Ipomoea has certain species of morning glory that are poisonous. Certain species of morning glory, including the common morning glory (Ipomoea purpurea), produce seeds that are rich in alkaloids, such as ergot alkaloids and lysergic acid amides. These seeds can cause symptoms including nausea, vomiting, hallucinations, and in extreme circumstances, organ damage or even death, when consumed.

Additionally, morning glories have the potential to spread rapidly, displacing native plant species and decreasing biodiversity in some regions. They have the potential to spread quickly and stifle other plants due to their robust growth and prodigious seed production.

Even though morning glories are not intrinsically harmful to people or animals when they come into contact with them, it is nevertheless advisable to use caution when eating some species’ seeds and considering the possible ecological effects of their invasiveness.

Beach Morning Glory.

Morning glory plants (pictured) are beautiful, but also toxic and invasive.

©jirasak_kaewtongsorn/Shutterstock.com

5. English Yew

Classification: Taxus baccata

The English yew is a coniferous tree native to Europe. It is a member of the Taxaceae family and is distinguished by its crimson berries and dark green needles. English yews may grow to astonishing heights of up to 60 feet and have a thick, pyramidal growth habit.

Although English yews are not indigenous to Pennsylvania, they are occasionally planted in gardens and other environments as decorative trees. They favor well-drained soils and are tolerant of a range of environmental factors. However, because they are not native to Pennsylvania, it is uncommon to see them in the wild there.

Although English yews are beautiful, it’s vital to remember that both humans and animals are extremely poisonous to them. A poisonous substance called taxine is found in all parts of the tree, including the leaves, bark, and seeds. Human cardiovascular and neurological systems can suffer serious toxicity from ingesting any portion of the English yew. Yew poisoning can cause fainting, respiratory problems, irregular pulse, convulsions, and even death.

Yew poisoning can also occur in animals as well, including pets and cattle, if they swallow any tree material. It is fatal to consume even little doses. It’s essential to keep animals away from English yews and to get veterinary help right once if you suspect ingestion. English yews should be treated carefully due to their severe toxicity, and it is best to stay away from planting them in locations where children or animals may get them.

English Yew Tree - Taxus baccata

English yews are extremely poisonous to humans and animals.

©Peter Turner Photography/Shutterstock.com

6. Oleander

Classification: Nerium oleander

This entry on our list of dangerous plants in Pennsylvania is actually quite popular as an ornamental plant. Oleander is a Mediterranean native perennial evergreen plant. It is a member of the Apocynaceae family and is distinguished by its spectacular clusters of blooms that are available in a variety of hues, including pink, red, white, and yellow, and its leathery, dark green leaves. Oleander is a commonly grown decorative plant that may be seen in many places throughout the world in gardens, landscapes, and public areas.

Oleander is a non-native plant that is typically grown in containers or greenhouses in Pennsylvania. It is uncommon to see it growing outside in Pennsylvania’s natural habitat since it prefers warm conditions. However, the flower is nonetheless popular in the Keystone State.

Oleander is extremely harmful to both humans and animals, despite its beauty. Cardiac glycosides are present in all parts of the plant. These glycosides are strong poisons that can seriously harm one’s health when consumed or even while in touch with the sap. The symptoms of eating oleander leaves, blossoms, or seeds include nausea, vomiting, lightheadedness, and irregular heartbeat. In extreme circumstances, it can cause cardiac arrest or death. Oleander also poses a risk when used as firewood or during controlled burns due to the fact that the smoke it produces when burning can be hazardous if ingested.

Oleander should only be pruned or handled with the utmost care while wearing gloves and protective equipment. To avoid accidental intake, keep oleander away from the reach of children and animals. If exposure or ingestion happens, you should get medical help right once.

oleander

Oleander (pictured) has toxic sap that can cause illness if ingested.

©iStock.com/Katrin_Timoff

7. White Baneberry

Classification: Actaea pachypoda

Eastern North America is home to the perennial herbaceous plant known as the white baneberry. It is known for having clusters of white berries with black dots that resemble miniature doll’s eyes. It’s also a member of the Ranunculaceae family. Stream banks, shady locations, and damp forests are the usual habitats for the plant.

White baneberry may be found in Pennsylvania’s woodland understory, especially in the eastern and central regions of the state. It does best in cold, shaded locations and favors rich, well-drained soils.

Although the berries of the white baneberry may seem attractive, both people and animals should avoid eating them. The glycoside actein and other cardiogenic poisons are present throughout the entire plant. Any part of the plant that is consumed, especially the berries, can cause serious health effects. White baneberry poisoning can cause nausea, vomiting, stomach discomfort, disorientation, an irregular pulse, and, in severe cases, cardiac arrest or respiratory failure.

White baneberries should not be handled or consumed, so use caution if you happen to find one growing on your property or nerby. Children could be drawn to the berries of the plant. Therefore, it’s important to inform them of any potential risks. In order to avoid unintentional poisoning, pet owners should be aware of their animals’ availability to white baneberries. To guarantee the safety of your family and animals, make sure there is no white baneberry on your property, and be sure to study the plant’s appearance. Understanding what white baneberry looks like serves as a reminder of the value of identifying and avoiding potentially hazardous plants in residential natural settings.

Actaea pachypoda doll's-eyes

Doll’s eye can grow up to 18-30 inches (46-76 cm) tall.

©Alex Polo/Shutterstock.com

8. Fly Poison

Classification: Amianthium muscaetoxicum

The perennial herbaceous plant called fly poison is indigenous to eastern North America, including Pennsylvania. Its tall, narrow leaves and clusters of white blooms make it distinctive. Typically, fly poison can be found growing in open meadows, woodlands, and beside stream banks. Fly poison is present across Pennsylvania, although it is most prevalent in wet, shady forests. It does best in regions with partial sunshine and requires rich, well-drained soils.

Despite its name, fly poison can be harmful to both people and animals in addition to flies. The plant as a whole includes poisonous alkaloids including zygacine and muscaetoxin. Serious toxicity can result from ingesting any component of the plant. Dizziness, weakness, tremors, convulsions, nausea, vomiting, stomach pain, and, in severe situations, respiratory failure or cardiac arrest, are just a few of the symptoms that might occur.

Animals are often repelled by fly poison’s toxicity and don’t attempt to eat it. Accidental ingestion, however, may happen when there is a lack of food in their environment or when one plant species is mistaken for another. So, be careful with your pets, especially dogs!

Fly poison should be handled carefully due to its toxicity. The plant may deceive you with its appealing look and white blossoms, which is why there is so much value in poisonous plant awareness and prevention.

How was our list of dangerous plants in Pennsylvania? If you come across any of these poisonous or toxic plants, be very careful and always avoid ingesting them. 

Fly poison is beautiful but toxic.

©homeredwardprice/CC BY 2.0 – Original / License

Summary of the 8 Most Dangerous Plants in Pennsylvania

NumberDangerous Plant
1Wild Parsnip
2Creeping Thistle
3Virginia Creeper
4Morning Glory
5English Yew
6Oleander
7White Baneberry
8Fly Poison


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About the Author

Em Casalena is a writer at A-Z Animals where their primary focus is on plants, gardening, and sustainability. Em has been writing and researching about plants for nearly a decade and is a proud Southwest Institute of Healing Arts graduate and certified Urban Farming instructor. Em is a resident of Arizona and enjoys learning about eco-conscious living, thrifting at local shops, and caring for their Siamese cat Vladimir.

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