Watch Out! 10 Poisonous Plants In Illinois That Need Precaution

Behind the diversity and beauty of the plant world in Illinois, it turns out that some poisonous plants in Illinois need to be aware. They can get you into trouble when you touch, swallow, or inhale any plant part.

In addition, the mildest symptoms usually observed are redness, irritation, and swollen skin. However, the poisoning can cause fatal events, such as respiratory failure, which leads to death.

Therefore, we are here to help you identify poisonous plants in Illinois and the symptoms that may occur when you have direct contact with these plants. Hopefully, it will help you prevent unwanted events in the future. Without any further ado, let’s get into the list!

Poisonous Trees in Illinois

Maybe all this time, we have focused on poisonous plants in Illinois with low-growing habits. Some trees are also toxic and, of course, dangerous for animals and humans. Let’s take a look at poisonous trees in Illinois you should know before it’s too late!

poisonous plants in illinois
Poisonous Trees in Illinois

1. American Holly

Holly’s family has long been known as one of the poisonous plants in Illinois. One of the members is American Holly. It has bright red berries and deep evergreen, glossy leaves that create striking contrasting colors.

poisonous plants in illinois
American Holly

Even though the fruits look attractive, they are risky to eat because they contain several toxic compounds, including saponins, sterols, alkaloids, and terpenoids. Some symptoms related to American Holly poisoning are vomiting, diarrhea, dehydration, and drowsiness.

poisonous plants in illinois
American Holly Fruits

2. Black Locust

Despite having ‘black’ on its name, Black Locust has no black flowers or leaves at all! Instead, it bears beautiful clusters of white blooms that hang on the green foliage.

Contrary to its stunning features, some parts of this plant are toxic, such as bark, foliage, young twigs, and seeds since they contain toxalbumins. 

poisonous plants in illinois
Black Locusta

Furthermore, you will experience an uncomfortable feeling in your stomach after ingesting one of the parts mentioned. Some people also reported vomiting and having diarrhea. Besides humans, it is also poisonous to cats and dogs.

poisonous plants in illinois
Black Locust Tree

3. Elderberry

Having similar fruits to blueberries, Elderberry belongs to the Adoxaceae family. The cooked berries are safe to eat since the cooking process helps to eliminate toxic chemicals. It is also beneficial for your health to boost your immune system as they are rich in vitamins and antioxidants.

However, it is not the case with its roots, stems, and leaves.

poisonous plants in illinois

Those parts of the plant are considered toxic if eaten. Usually, poisoning occurs in children who often use their stems to play with blowguns. The mild poisoning signs include nausea, vomiting, and loose stools.

Additionally, the cyanide-inducing glycoside compound may lead to coma in cases of severe poisoning. Hence, hospitalization is necessary.

poisonous plants in illinois
Elderberry Flowers

4. Poison Oak

This Oak is one of the native plants of the Pacific Northwest that has attractive foliage, especially in autumn. This season, the green leaves will turn yellow to a red shade that will last for up to 2 weeks before falling.

poisonous plants in illinois
Poison Oak

Besides the exquisite leaves, this oak features acorns that are less toxic than other parts of the tree. Cooking processes, such as boiling, can remove the toxic compounds, making them safe to be cooked into acorn jelly.

However, you may experience kidney damage if you eat any part in its raw form.

poisonous plants in illinois
Poison Oak Leaves

5. Yellow Oleander

Displaying stunning yellow bell-shaped flowers, you cannot help but love this tree. It features lance-shaped, dark green foliage that matches beautifully with the vibrant blooms, making them great to grow in your garden.

Nevertheless, you must carefully consider the planting location as all parts of this tree, including the yellow flower, is toxic, especially its fruit kernels.

poisonous plants in illinois
Yellow Oleander

The common symptoms of yellow oleander poisoning are vomiting, numbness of the tongue and lips, giddiness, and diarrhea. Unfortunately, ingesting two seeds is fatal as they contain toxic cardio-active steroids that are potentially lethal.

poisonous plants in illinois
Yellow Oleander Flower

Poisonous Shrubs in Illinois

In addition to toxic trees in Illinois, we also include shrubs in the list of poisonous plants in Illinois. We think it is crucial because we may often encounter these plants. After all, they are low-growing plants, especially when exploring the forest. 

In addition, some of them are also a category of garden plants. Hence, this list will also help you determine their planting location safely.

poisonous plants in illinois
Poisonous Shrubs in Illinois

6. Canada Yew

At first glance, the Canada Yew is similar to the American Holly, except that the leaves are smaller and needle-like. It also has red, fleshy berry-like fruits, called Aril, which wrap around its tiny seeds. Although the berries are edible, the seeds are deadly toxic. Why is it so?

poisonous plants in illinois
Canada Yew

It is because they contain taxine alkaloids that cause cardiotoxicity. Even after you remove the seeds, it still concerns that the toxic chemical is still present in the flesh—the poisoning signs such as altered mental status, difficulty breathing, diarrhea, dizziness, and coma.

In addition to the seeds, the needles of this shrub are also poisonous.

poisonous plants in illinois
Canada Yew Fruits

7. Poison Hemlock

Featuring flowers like wild parsnip, Poison Hemlock is a member of the wild carrot family. It has petite white flowers atop thin flower stalks that look captivating. This herbaceous flowering plant loves sunlight; thus, it prefers open sunny areas to grow.

Unfortunately, its resemblance to wild parsnips makes people think the roots are safe to eat. In fact, they are extremely toxic.

poisonous plants in illinois
Poison Hemlock

Even in a small amount of ingestion, poison hemlock roots poisoning can be fatal to humans and livestock. Some signs of poisoning this flowering shrub are salivation, trembling, weak pulse, and dilated pupils. In cases of severe poisoning, the symptoms such as respiratory paralysis will lead to coma and death.

Hence, it is recommended to always wear protective clothing and eyewear while having contact with this plant.

poisonous plants in illinois
Poison Hemlock Flowers

8. Poison Ivy

This shrub is the most widespread toxic plant among all poisonous plants in Illinois. It generally bears pointy leaves with toothed edges and smooth, glossy surfaces. They can grow by climbing the tree or creating a carpet on the woodlands soil.

Although poison ivy is more of an allergenic plant, we should include this on the list because of its toxicity effect, which is quite bothering to the skin.

poisonous plants in illinois
Poison Ivy

Once you touch the leaves, you will have rashes, itching, swelling, and blisters on the skin, while difficult breathing may occur if you inhale the smoke from the burning leaves of poison ivy. These symptoms appear because of an allergic reaction to urushiol, an oily sap produced by poison ivy, poison sumac, and poison hemlock.

Like the previous shrub, you must wear protective clothing if you want to handle poison ivy.

poisonous plants in illinois
Poison Ivy Growing on Tree

9. Poison Sumac

Along with its sisters, Poison Sumac is one of Illinois’s most toxic and allergenic plants. You can identify the plant by its three leaflets, deep green foliage, and light-green berries arching down on the branches.

The leaves are also wider, without a pointed tip at the edges.

poisonous plants in illinois
Poison Sumac

Similar to Poison Ivy, this woody shrub produces an allergenic sap oil called urushiol that will cause redness, itching, and swelling skin when you touch the leaves. The bad news is those symptoms can last 8-48 hours to weeks.

They will stay longer, especially if you have a particular allergy to the oil.

poisonous plants in illinois
Poison Sumac Tree

10. Rhododendron

If the plants have dazzling flowers, it does not mean they are harmless, for example, this flowering plant.

Rhododendron is one of the poisonous plants in Illinois that you should watch closely, especially if you plant it in your garden, because the leaves and nectar are deadly toxic if ingested in large amounts.

poisonous plants in illinois

For those with sensitive skin, touching the rhododendron leaves may cause mild irritation. Meanwhile, swallowing it will lead to a burning sensation on the lips, mouth, tongue, and throat.

The worst-case happens if you ingest 3 ml nectar per kg body weight as a consequence will be life-threatening.

poisonous plants in illinois
Rhododendron Flowers

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FAQ (Frequently Asked Questions)

Is Poison hemlock invasive in Illinois?

Even though not being in the top three of the most invasive plants in Illinois, Poison Hemlock is still an invasive plant and also one of the toxic plants that can be fatal to humans. 

Are there stinging nettles in Illinois?

Stinging nettles are rarely naturalized and grow in Illinois. Some states in the U.S where you can commonly find stinging nettles are Arizona, California, Nevada, New Mexico, Oregon, Texas, and Washington.

Is there poison ivy in Illinois?

Poison Ivy is commonly found in Illinois. This poisonous plant is characterized by its green trifoliate leaves that will give you red, severe itching, and swollen skin if you touch them. Almost all parts of poison ivy are toxic. 

What does poison ivy look like in Illinois?

You can identify Poison Ivy in Illinois by its hairless medium green upper leaves, while the thin hair grows on the lower surface, or sometimes it is hairless too. It also grows yellowish-green flowers across the compound leaves. 

What is poison ivy used for?

Despite being a toxic plant, Poison Ivy is used to treat some health issues, such as menstrual period pain, itchy skin disorders, swelling, and rheumatoid arthritis.

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