Poisonous Plant Nature Study

It seems that we might have a theme going here. A couple of weeks ago we talked about the fact that some snakes can be venomous, and last week we talked about the fact that wasps have venom. Today, we’re talking poisonous plant nature study. I’m Mrs. Cindy from No Sweat Nature Study LIVE and here we go again with another vicious topic!

Poisonous Plant Nature Study

If I were to ask you to name a poisonous plant, could you name one? Or, maybe more than one?

Did you happen to name poison ivy, poison oak, poison sumac, or poison hemlock? Those are common ones to know because the word “poison” is part of their name.

Poisonous Plants Nature Study

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What’s poisonous about plants?

But what’s poisonous about them? Plants don’t slither nearby and sink venomous teeth into us like snakes. They don’t fly around with sharp, venomous stingers ready to plunge into our skin either. In fact, if plants don’t move around other than swaying in the wind, so why are we worried about their poison anyway?

Well, how many times have you taken a nature walk along a trail or through a field and rubbed up against a plant? I do that almost every time I take a nature walk. It’s hard not to brush past a plant when you’re walking in places where they grow. That being said, even though a poisonous plant can’t reach out and grab us, we can run right into one. But, again, why does that matter?

I bet you know that animals have defensive mechanisms, right? Sharp claws and teeth, stinky sprays, body armor like thick skin or a shell, and even venom are just a handful of defense mechanisms that can help animals escape danger. Believe it or not, plants have defensive mechanisms, too!

Wait. Why would a plant need to defend itself? It’s not like plants go after other plants to eat them or pick a fight. Ah, but animals and humans DO like to eat plants. So, for plants to have a chance at surviving long enough to grow, pollinate, and make seeds for new plants to grow, they need to have some defensive mechanisms.

deadly nightshade

Mechanical Defense Mechanisms

Some of their defenses are called mechanical defense mechanisms. A plant might have thorns, leaf edges that are serrated like a steak knife, or poky/stinging hairs called trichomes. Sometimes these weapons of sorts simply scratch us or animals as a warning to stay away, and other times these tools actually cut into the skin to deliver poison for a more frustrating reaction that might sting, burn, or itch for a few minutes – or a few weeks.

Not too long ago, I was picking green beans in the garden in short sleeves. We’ve grown green beans in our garden for years, but planted a new variety this year. Much to my surprise, a couple of hours after digging through the plants to find and pick off the yummy beans, I started developing painful blisters up and down the underside of my forearms. These particular beans didn’t have a mechanical defensive mechanism, but a chemical one.

stinging nettle

Chemical Defense Mechanisms

A chemical defense mechanism is when a plant produces a toxic oil or sap that causes irritation like my blisters. Poison ivy, poison oak, and poison sumac each produce an oil that can cause itchy, burning, blistery rashes like this.

Interestingly, my skin isn’t sensitive to the oils of poison ivy. If I were to accidentally rub up against a poison ivy plant, I most likely wouldn’t break out in any sort of blisters. Some of my friends, on the other hand, can get terrible blistery rashes from simply touching the oil on clothes that have brushed past a poison ivy plant.

Just like not everyone is allergic to peanuts or not everyone has an allergy to pollen flying around in the air, not everyone reacts to plant poisons the same way. This goes for animals, too. In fact, some animals can eat plants that would kill other animals.

Poisonous Plants That Kill

For instance, butterfly milkweed is a pretty famous plant because monarch butterflies lay eggs on milkweed plants and the larvae eat the leaves before turning into pupae. But, believe it or not, if a cow finds a clump of milkweed and eats a couple of pounds of the plant, it can die.

Speaking of eating plants, poison is one reason we never eat plants in the wild unless we’re with someone who knows exactly what a plant is and that it’s entirely safe to eat.

Let me tell you one more interesting poison story. On our farm grow a bunch of beautiful Queen Anne’s Lace. These plants have dainty, flat, lacy, white flower heads growing on tall, slender stems. We also have poison hemlock growing on our farm. They have dainty, flat, lacy, white flower heads growing on tall, slender stems. Did you hear the similarities in the descriptions there?

Queen Anne's lace and poison hemlock

To the untrained eye, the flowers look almost identical. One is perfectly safe to touch, but the other can be deadly. Because they look so much alike, until my children are very much old enough to tell the difference between the two, I ask them to stay away from both plants when wandering around the farm.

If this topic fascinates you, you should definitely dig deeper using the Defense Mechanisms of Plants study that you can find in the Our Journey Westward Shop. This resource will help you discover more about the defense mechanisms we’ve talked about, plus some other ones, through interesting videos and engaging books. You’ll be encouraged to do some nature journaling, take some nature walks, and even do some hands-on activities and experiments if you want.

Poisonous Plant Nature Study Challenge

For our nature walk, we certainly don’t want to go on the hunt for poisonous plants that could potentially hurt us with their mechanical or chemical weapons!

However, I think we can safely look for some plants that have obvious mechanical defense mechanisms. It’s pretty easy to find plants with prickly things like sharp leaves, thorns, or even bristly stems. As long as you’re careful not to scratch yourself with their weapons, you can get close enough to observe them so you can make a detailed drawing in your nature journal.

You can likely take a walk around your neighborhood to find several specimens to observe.

poisonous plants

Or, learn to identify four of the most common poisonous plants that you might see on a nature walk – poison ivy, poison oak, poison sumac, and poison hemlock as seen below. Draw each and write their names beside them so that you can easily recognize them and stay away on future nature walks.

I hope you’ve had fun with this poisonous plant nature study! I’ll see you next week for the last episode of this season when we learn about pondweed. Until then, happy nature exploring!

Nature Walk Curriculum

Links and Resources

Handbook of Nature StudyThe Handbook Of Nature Study in Color - Wildflowers, Weeds & Cultivated CropsA Field Guide To Poisonous And Wicked Plants: World's Most Poisonous Plants You Can KnowCommon Poisonous Plants and Mushrooms of North AmericaCanson 100510926 XL Mix Media Paper Pad, 98 Pound, 7 x 10 Inch, 60 SheetsAmazon Basics Premium Colored Pencils, Soft Core, 24 Count (Pack of 1)


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    1. Just a quick FYI – the final pic of the poison sumac. If the berries are red the species isn’t poisonous, if white it is

    2. Thanks! We don’t have poison sumac around here, so I learned something new. 🙂

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