Poisonous plants in CT can pose a threat to your safety and that of your loved ones if adequate caution is not exercised. Forewarned is forearmed, so gaining knowledge of the various toxic plants in Connecticut is a step toward your safety.

Poisonous Plants in Connecticut Worth Watching

Whether you are simply walking around, biking, or watching nature, you need to have an informed awareness of your environment. This article will make this easier for you by highlighting some of the poisonous beauties that you might not have known about.

A List of Poisonous Plants in Connecticut That You Should Avoid

The poisonous plants in CT can make a long list that includes species like the hemlock, poison ivy, giant hogweed, castor bean and poison sumac, just to mention a few. These plants cause a wide range of symptoms, some of which we presented in this article. 

As we have included information about the growth and survival needs of these poisonous plants, you will have ideas of places where they are most likely to grow. The distinguishing characteristics will help you identify these plants so that you avoid contact if need be.

1. Atropa belladonna

Understanding Atropa Belladonna

Growing season
  • Spring and summer
Distinguishing characteristics
  • Berry-like fruits are oblong and bright red in color
  • Flowers have purple and yellow colors
  • Has a characteristic foul smell
Growing conditions
  • It grows well under full or partial shade and sometimes even when it’s not shielded from the sun at all
  • Prefers soils that are loamy, sandy, or rocky, especially when the pH is below 6
  • Thrives in temperatures between 68 and 78 degrees Fahrenheit
Toxic compounds
  • Atropine, scopolamine and hyoscyamine

This plant is a member of the Solanaceae family. Atropa belladonna is also known as the deadly nightshade, further indicating the toxic nature of the plant. This plant mainly grows in woodlands or spaces that are shady. Symptoms of its negative effects are elevated pulses, and in worst-case scenarios, paralysis occurs.

2. Lily of the Valley

The Poisonous Lily of the Valley

Growing season
  • Spring
Distinguishing characteristics
  • Has white, bell-like flowers with a characteristic sweet odor
  • The plant grows up to 12 inches
  • Has lush green leaves
Growing conditions
  • Is not choosy with regard to soils so it can grow in mediums lose, moderate, or compacted soil structures
  • Grows well in partial or full shade
  • Thrives best in temperatures that are around 60 to 70 degrees Fahrenheit
Toxic compounds
  • Cardiac glycosides

The scientific name for this plant is the Convallaria majalis. This plant, whose origins are in Eurasia, belongs to the Asparagaceae family of plants. The lily of the valley plant is less likely to be poisonous upon contact, but the danger is certain when you consume it.

3. Poison Ivy

Recognizing the Threat of Poison Ivy

Growing season
  • Spring and summer
Distinguishing characteristics
  • It can grow as a climbing vine or as a shrub
  • Produces white berries that are quite small
  • Leaves are smooth
Growing conditions
  • Soils that are acidic and void of nutrients such as selenium and phosphorus
  • Develops well both in full sun and shade
  • Prefers high humidity and temperature conditions
Toxic compounds
  • Urushiol

This plant is scientifically referred to as the Toxicodendron radicans. Poison ivy can cause serious dermatitis, which is a skin condition, in the event that contact happens. Please seek medical attention as soon as possible under such circumstances. Burning this plant or even smoking it can also have detrimental effects.

4. Giant Hogweed

The Dangers of Giant Hogweed

Growing season
  • Early spring
Distinguishing characteristics
  • Stems are green and are covered with white hairs and purple blotches
  • Produces clusters of white flowers
  • Can reach a maximum height of about 14 feet
Growing conditions
  • Prefers exposure to high levels of sunlight
  • Grows in soils that are nutritionally rich and damp but not necessarily soggy
  • Grows well under warm temperature conditions
Toxic compounds
  • Furanocoumarins

The scientific name of this plant is Heracleum mantegazzianum. Any contact with the plant may result in poisoning symptoms like dark blisters that are usually very painful. These blisters can be noted approximately 48 hours after contact has been established with the hogweed plant, but the actual poisoning effects would have started within 15 minutes after exposure.

5. Water Hemlock

The Perils of Water Hemlock

Growing season
  • Early spring
Distinguishing characteristics
  • Flowers are white, small, and arranged in a cluster-like format
  • Thick rootstock has small chambers
  • Side veins don’t lead to the tips at the outer margins but to notches
Growing conditions
  • Thrives best under exposure to partial sun, though it can also survive in direct sun and completely shaded areas
  • Prefers well-drained soils when the pH is less than 7
  • Does not grow below 45 degrees Fahrenheit
Toxic compounds
  • Cicutoxin

The water hemlock is also known as the poisonous marsh plant, and it falls under the carrot family. All parts of this plant trigger toxic effects upon consumption or contact with the skin. The plant can lead to death within 15 minutes of unsafe contact. 

The symptoms that are associated with water hemlock poisoning range from mild, like vomiting, sweating, and stomach pain, to more severe ones like disrupted breathing and convulsions, as well as kidney and heart issues. Check out a list of plants that look like Poison Hemlock to be able to identify it and avoid it!

6. Castor Bean

The Hazards of Castor Bean

Growing season
  • Rainy season
Distinguishing characteristics
  • Produces seed capsules that are reddish-brown in color
  • Leaves have about five to 11 pointed lobes with an appearance that resembles the fingers of an open palm
  • Leaves have a glossy green color
Growing conditions
  • Needs exposure to at least eight hours of full sunlight every day
  • Grows in soils that are well-draining, moist, and nutritionally rich, with pH ranges of 7 and below
  • Grows in temperatures that range between 50 and 64 degrees Fahrenheit
Toxic compounds
  • Ricin

This plant contains a substance called ricin, which is responsible for its toxicity. The effects of this poisonous substance can also be experienced even after inhaling the dust from the beans. The main negative effects are related to the respiratory system. In the event of any related symptoms, be quick to seek professional health care attention.

7. Cow Parsnip

Giant Wild Parsley Cow Parsnip

Growing season
  • Spring
Distinguishing characteristics
  • Produces white blooms that are arranged in clusters of approximately 30 flowers
  • The mature version grows up to around 10 feet
Growing conditions
  • Prefers partly shaded spaces
  • Grows well in soils whose moisture levels range from moist to semi-we, as long as they are well-draining
  • Requires temperatures between 60 and 65 degrees Fahrenheit for optimum growth
Toxic compounds
  • Furanocoumarins

Heracleum maximum is the scientific name for cow parsnip. You are more likely to find the cow parsnip in fields that are moist, if not in streambanks. Its poisonous effects are experienced when contact is established between the skin and the plant.

This may result in a rash that deteriorates when the skin is exposed to sunlight due to the reaction between the plant poison and the light from the sun.


You have just reached the end of a poisonous plants list for CT. You might want to go through the following summary of points before you go:

  • Some of the plants that stand out as poisonous plants of CT are the lily of the valley, poison ivy, giant hogweed and castor bean.
  • The growth requirements of these plants vary, but many can be found on roadsides or uncultivated terrain.
  • The toxic effects are usually experienced after an established contact between the plant and the skin, though some are also poisonous upon consumption.
  • Extra care should be taken, considering that some of the plants, like the lily of the valley, are quite beautiful and attractive.
  • We recommend that you see healthcare professionals for assistance in the event of any rashes or other symptoms, such as vomiting and breathing difficulties.

If you have been wondering “What plants are poisonous to touch in CT?” this article enlightened you about some of this toxic flora. Now, the ball is in your court – do everything possible to enhance your safety and that of your loved ones.


  • http://bioweb.uwlax.edu/bio203/s2013/lambert_made/habitat.htm
  • https://plants.ces.ncsu.edu/plants/convallaria-majalis/
  • https://ag.umass.edu/landscape/fact-sheets/poison-ivy
  • https://ag.umass.edu/landscape/fact-sheets/hemlock-woolly-adelgid-frequently-asked-questions
  • https://www.webmd.com/vitamins/ai/ingredientmono-948/water-hemlock
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