Poisonous plants in NJ can be poisonous to both people and animals. It is key to know that gardeners and homeowners need to familiarize themselves with the different types of these plants.

Poisonous Plants to Watch Out For

From common household weeds to more exotic species, this list of poisonous plants in New Jersey contains all the details about different plants. You can have a look at the descriptions below.

Different Types of Poisonous Plants in NJ

1. Foxglove

The Fascinating but Deadly Foxglove

Growing Season
  • Spring 
  • Fall
Leaf Shape Spear-shaped
Specific Needs
  • Light shade or full sun
  • Any type of soil but moderately wet
Common Pests Mealybugs 

Foxglove is a toxic, invasive biennial plant that is native to Europe but now grows on every continent except Antarctica. In New Jersey, Foxglove thrives in wet, open areas such as pastures and roadsides. 

All parts of the plant contain cardiac glycosides which can cause irregular heart rhythms if ingested and irritation or contact dermatitis if touched. Which means that one must stay away from it, and not intend to take the risk in any way possible.

While it may be beautiful with its tall stalks of pink to purple flowers, the sap can also cause skin irritations. It is essential to take necessary precautions when dealing with this dangerous plant.

2. Poison Sumac

Itchy and Unpleasant Poison Sumac

Growing Season
  • Summer
  • Spring
Leaf Shape
  • Pointy
  • Oval
Specific Needs
  • Wet soils
  • Part or full sunlight
Common Pests
  • Aphids
  • Spider mites

Poison Sumac is a toxic shrub native to New Jersey and parts of the US. Recognizable by its white berries, this plant contains urushiol oil, an allergen that causes skin irritations such as redness, swelling, blisters, and itching in humans who come into contact with it. Inhalation of its smoke can also cause symptoms, such as hurting the lungs in some cases.

To avoid contact, it is important to be aware of and recognize poison sumac’s growth habitats which can include wet areas such as marshes and swamps, or dryer locations such as sandy soils or dry fields. Keep in mind that when you are dealing with infestations on private property it’s advisable to wear long-sleeved clothing and rubber gloves when removing the plant from the area.

3. Monkshood

Deadly Monkshood A Cautionary Tale

Growing Season
  • Summer
  • Fall
Leaf Shape Lanceolate
Specific Needs
  • Part shade
  • Moist soil with good drainage
Common Pests No pests 

Monkshood is a toxic and potentially deadly plant found in New Jersey. This perennial herbaceous flowering species belongs to the buttercup family and grows up to five feet tall with purple or blue flowers tinged with white and yellow, and single-seeded fruits. 

When it comes to the toxicity of this plant, remember that all parts of the plant are poisonous, containing several deadly alkaloids such as aconitine, mesaconitine, hypaconitine, and jesaconitine.

The alkaloids present to cause symptoms of nausea, vomiting, trembling limbs, paralysis, cardiac irregularities, and even death in humans when it is given in an abundant amount and animals if ingested or even touched in some cases. As a whole, remember that it is advisable to avoid contact with monkshood when encountered in the wild, especially if one has open cuts or wounds on the skin.

4. Poison Hemlock 

The Lethal Poison Hemlock

Growing Season All year round
Leaf Shape Triangular
Specific Needs
  • Moist soil
  • Part or full sunlight
Common Pests Aphids

Poison hemlock or Conium Maculatum is a dangerous, toxic plant that is native to New Jersey and can be found growing in meadows, along roadsides, and in other disturbed areas. The plant has a height of up to seven feet with umbels of small white flowers atop the stems, as it could be seen in some common parts. When you see it, remember that all parts of the plant are considered poisonous, containing piperidine alkaloids such as coniine that can cause central nervous system paralysis when ingested.

If an individual encounters this plant it is recommended, they do not touch it or breathe near it due to potentially high levels of toxins in smoke resulting from burning it. The best approach when encountering Poison Hemlock is to avoid contact altogether.

5. Poison Ivy

The Infamous Poison Ivy

Growing Season
  • Spring
  • Summer
Leaf Shape Rounded
Specific Needs
  • Moist but well-drained soil
  • Partial shade or full sunlight
Common Pests
  • Beetles
  • Flies

Poison ivy is commonly found in the Northeast U.S., and is a common poisonous plant in New Jersey. It is primarily a woody perennial, appearing as either an herb or shrub depending upon its stage of growth; young plants appear more densely foliated and vine-like, whereas mature poison ivy has three leaflets that provide noticeable serration along the edges.

All parts of this plant contain an oily sap known as urushiol which can cause skin irritation unless carefully removed with bleach or soap and water. Serious blistering rashes along with swelling, itching, and redness can occur if contact cannot be avoided, which is extremely worrying so don’t risk it. Taking preventive measures against Poison Ivy should be strongly considered.

6. Poison Oak

The Misunderstood Poison Oak

Growing Season Spring
Leaf Shape Rounded/irregular
Specific Needs
  • full sunlight
  • Moist Soil
Common Pests
  • Spider Mites
  • Whiteflies

Poison Oak is a poisonous plant native to parts of New Jersey and found in other states throughout the northeastern United States. It can be distinguished by having three leaves which may vary in hue from yellows to greens, red or purple, as well as its bumpy texture.

The plant releases an oil called urushiol when it is touched or brushed up against, which reacts with the skin cells of most people and causes an allergic reaction that appears as an itchy and painful rash, and it is best to avoid it. Wearing long sleeves and pants while walking in any area known to contain poison oak is highly advised to minimize the risk of exposure.

7. Water Hemlock

How to Identify and Avoid

Growing Season
  • Spring
  • Fall
Leaf Shape Lance-shaped
Specific Needs
  • Mulches on the ground
  • Full shade tolerable
Common Pests
  • Aphids
  • Mealybugs

Water Hemlock is an endemic poisonous plant found in New Jersey and is one of the most toxic plants in North America. It thrives in wet, marshy areas and can contaminate both surface water and groundwater sources. The entire plant is highly toxic if consumed, with the roots containing a particularly powerful cicutoxin.

When you get intoxicated some of the symptoms of ingestion may include abdominal pain, delirium, convulsions, seizures, and death. Even touching bare skin can result in painful irritation for some individuals. Because of its potential danger to humans, it is important to take caution when interacting with this plant species or visiting habitats where it occurs.


The different types of poisonous plants in NJ that we have talked about here grow in different seasons as we have already mentioned. To summarize that at a glance:

  • You should keep an eye out for Poison Sumac, Monkshood, and Poison Ivy during the summer season.
  • During the fall season, you should stay safe from Foxgloves, Monkshood, and Water Hemlock.
  • Foxgloves, Poison Sumac, Poison Ivy, Poison Oak, and Water Hemlock are all found during the spring season.
  • Only the Poison Hemlock plant can be found growing all year round in New Jersey.

Now that you have the knowledge about which dangerous plants thrive in which season in New Jersey, you can easily avoid these plants.

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