Poisonous plants in Idaho exist in various forms, but the common aspect between all of them is that they contain toxic substances that may harm your health or in worst-case scenarios, take your life.

Surprising Poisonous Plants in Idaho

If you have been wondering if there are poisonous plants in Boise, Idaho and other parts of this state, the answer is a resounding “Yes.”

This article will take you on a ride exploring different poisonous plants that grow in Idaho, for both information and safety purposes.

The “One-Stop” Index for Poisonous Plants in Idaho

The poisonous plants in Idaho include but are not limited to water hemlocks, poison sumac and poison ivy. Some of these plants appear so innocent due to their gorgeous look, so knowing their poisonous effects is a plus, especially when you have children and pets, both of whom might be affected. 

In this section, we will go through various aspects that are associated with these plants, including their specific characteristics and the toxins they contain, so that you can easily identify them.

1. Dogbane

Beware of the Poisonous Dogbane

Growing season
  • Perennial
Distinguishing characteristics
  • Stems are hairy
  • Grows in an upright manner 
  • Leaves have smooth margins and a pointed apex, in addition to having an elliptical shape
Growing conditions
  • Grows well both in full sun and partial shade
  • Grows in soils that have good moisture-retaining abilities
  • Loves temperatures that range from 75 to 95 degrees Fahrenheit
Toxic compounds
  • Cymarin

When it comes to the dogbane, Idaho residents are aware that it is similar to plants that you can find in any other place, just that there are slight compound variations that depend on changing climatic conditions. The toxicity of dogbane is mainly due to a substance that is called cymarin, which is harbored by this plant. Both green and dried dogbane plants cause death within six to 12 hours.

2. Death Camas

The Dangers of Death Camas

Growing season
  • Early spring
Distinguishing characteristics
  • Leaves have parallel veins
  • Flowers grow in a cluster arrangement, and they exist in cream or white colors
Growing conditions
  • Rocky and sandy soils 
  • Grows in places with sun exposure
  • Prefers temperatures that are cool
Toxic compounds
  • Zygacine

A component called zygacine is the main toxic substance that is found in the death camas. The mature leaves and bulbs are the parts that are highly poisonous, probably because they contain more of the zygacine. Some of the symptoms that you should be on the lookout for after “death camas” poisoning are burning lips, profuse salivation, thirst, and numbness of the mouth.

3. Stinging Nettle

The Hazards of Stinging Nettle

Growing season
  • Late fall to early spring
Distinguishing characteristics
  • Stems and leaves are covered with hairs that are packed with irritating chemicals
  • Can grow to a height of about 6.5 feet
  • Leaves have smooth surfaces and toothed margins
Growing conditions
  • Soils that are nutritionally rich and damp
  • Grows in places with full sun exposure 
  • Has average water needs
Toxic compounds
  • Tartaric acid and oxalic acid

The stinging nettle Idaho has is also similar to the one that is found in other regions, save for the slight differences in phytochemical composition. This plant is not completely toxic, considering that if you follow directions on how to use or handle it, the stinging nettle will be relatively safe. 

However, failure to follow specific directions of use may lead to symptoms such as sweating, rash, stomach issues, diarrhea, and fluid retention. Therefore, we recommend that you exercise caution when you deal with this plant.

4. Poison Ivy

The Perils of Poison Ivy Plant

Growing season
  • Summer and spring
Distinguishing characteristics
  • Each of the leaves has three leaflets
  • Can grow either as a vine or shrub
  • In summer, the leaves are green; in spring, they turn reddish; in fall, they go through a color transition to orange, yellow, or red
Growing conditions
  • Prefers poor soils that lack some nutrients, especially calcium, selenium, and phosphorus
  • Does well in both the shade and full sun
Toxic compounds
  • Urushiol

The toxic substance in poison ivy is urushiol, which causes allergic reactions if it comes into contact with your skin. Urushiol can stick on equipment, clothes, and the fur of pets, so even if you don’t get into direct contact with a poison ivy plant, if your skin rubs to a contaminated surface, you will still be affected. 

The most notable symptom that such contact has established is skin rashes. The best way to avoid having to deal with the negative effects of poison ivy is by making sure that it doesn’t grow in your yard.

5. Water Hemlock

The Threat of Water Hemlock

Growing season
  • Spring
Distinguishing characteristics
  • Flowers are tiny, white, and exist in clusters that are umbrella-shaped
  • Has a thick rootstalk that contains a brown-colored liquid that is extremely poisonous
  • Has thick and fleshy tubers that grow extending from the thick rootstalk
Growing conditions
  • It grows in soils that are acidic and relatively cool
  • This plant thrives in partial sunlight, though the plant can still live in conditions with either full light exposure or shade
Toxic compounds
  • Cicutoxin

Water hemlock is also called Cicuta, and it belongs to the Apiaceae family of plants. This plant contains a toxic substance called cicutoxin, which is the force behind its poisonous nature. Small amounts of cicutoxin can directly have detrimental effects on the central nervous system, which is why this plant is quite deadly. It causes violent convulsions.

6. Milkweed

The Deceptive Beauty of Milkweed

Growing season
  • Fall and spring
Distinguishing characteristics
  • Fruits and blossoms appear simultaneously
  • Flowers are greenish-white in color and they grow in clusters that are umbrella-shaped
Growing conditions
  • Grows in soils that are slightly acidic, with pH ranges between 4.8 and 6.8
  • Grows well in places with many hours of sunlight
  • Develops well when temperatures range from 65 to 75 degrees Fahrenheit
Toxic compounds
  • Cardenolides

The foliage of the milkweed is very poisonous. These aerial parts of the plant harbor substances that are referred to as cardenolides, and these are the ones that aid its toxic nature. Some of the common symptoms of poisoning by the milkweed are increased temperatures, respiratory discrepancies, depression, and feeling weak. Please note that this plant mainly grows on abandoned grounds such as uncultivated farms and roadsides.

7. Poison Oak

Risks of Poison Oak Rash Maker

Growing season
  • Summer 
Distinguishing characteristics
  • Like the poison ivy, leaves have three leaflets, but the tips are rounded
  • Has a shrubby nature of growing
  • May produce yellow or white berries
Growing conditions
  • Dry, sandy soils 
  • Prefers exposure to direct sunlight
  • Needs water during early spring
Toxic compounds
  • Urushiol

The response to the question, “Does Idaho have poison oak?” is “Yes, it does.” The reason why this plant is poisonous is that it has urushiol, so any form of bruises or damage on the plant parts will expose this substance. If urushiol gets onto your skin, you will experience itchiness of the skin as a result of the poison oak rash. Make sure to check the following list of plants that look like poison oak in order to be able to identify which is which!

8. Poison Sumac

The Dangers of Poison Sumac

Growing season
  • Summer and spring
Distinguishing characteristics
  • Light green or white berries are produced in clusters, unlike the red ones that are produced by harmless sumac
  • Berries tend to sag downward, unlike those of the harmless sumac, which are upright
  • Leaflets have smooth edges compared to the toothed ones of the harmless version
Growing conditions
  • Both partial shade and full sun are conducive to the plant’s growth
  • Can tolerate soils that are sandy or loamy, with a touch of moisture retaining capacity
Toxic compounds
  • Urushiol

The scientific name of this plant is Toxicodendron vernix. Just like poison ivy, this plant also contains a toxic substance called urushiol. This substance irritates the mucous membrane and skin. Even inhaling the smoke when the Toxicodendron vernix is burned can trigger symptoms such as diarrhea, so do not hesitate to seek medical assistance if you have a high fever.


At this point, we assume that you now have a bigger picture of the various poisonous plants that are found in Idaho. We have prepared a special “take home” message that summarizes what you learned in this article:

  • Idaho has many poisonous plants that are worth noting and these include stinging nettle, poison oak, death camas, dogbane and poison oak.
  • These plants cause toxic effects via skin contact, consumption, or inhalation of the smoke upon being burned.
  • Some of the common symptoms to look out for include diarrhea, fever, and breathing problems.

You have just been equipped with the knowledge of plants that potentially pose a risk to your health and life. Now, you can be more careful as you practice plant enthusiasm in your home and even outside your yard.















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