Meet the Poisonous Plants In Your Backyard

Lily of the Valley (Convallaria majalis). Pretty, delicate, toxic. Image credit: Leo-seta.

Sadly, the internet tells me that there’s no such thing as a toxophile or toxicophile. If there were, I’d make a blog button for it. (Other suggested blog buttons for my site: Anti-Social Media Expert — thanks, Karen — and Evolutionary Dead End. Alas, I don’t know how to make buttons.) Anyway, what I mean to say is that I kind of have a thing about poisons. And by thing, I mean that people who look too closely at the books on my bookshelf might decline an invitation to dinner.

This is what comes of reading too many Agatha Christie books at a young and impressionable age.

Plant poisons are my favorite. I’m always taken aback by how elegantly and creatively nature addresses the problem of being eaten. Plants can’t run, so instead they wage chemical warfare on their predators. The Indian bean tree, for example, produces a nectar with a compound that only affects cheater species that steal nectar — but not pollinators.

And plenty of plants are well-protected not just against insects, but also bigger animals, like humans. There are lots of them, and they’re all around us. I’ve pulled together some of my favorite common wicked plants, a number of which are probably in either your backyard or a backyard near you. Welcome to my virtual poison garden!

(And for crying out loud, teach your kids to respect plants. I sampled my way through my mom’s garden as a kid and got lucky she didn’t have anything really poisonous. Although I guess that could explain some of my peculiarities.)

Nerium oleander. Image credit: heatheronhertravels

Oleanders are, in a sense, perfect garden shrubs. They’re drought resistant, have nice foliage, and produce lovely symmetrical pinwheel flowers that smell nice. They’re also among the deadliest of common garden plants, possessing a number of cardiac glycosides that affect heart function and can cause death. Even honey made from oleander nectar is toxic. (Most deaths by oleander, however, are intentional. By anecdote, a number of seniors have ended their lives by drinking oleander tea because it was readily available in their nursing home garden. That story makes me sad.) Interestingly, oleanders are also being investigated for therapeutic uses in treating cancer. The dose makes the poison.

Viburnum lantana. Image credit: Bosc d’Anjou

Lantanas have peppy colored flowers and nice leaves, but that’s about where the good news ends. They’re invasive in Australia, Hawaii, South Asia, and Southern Africa because 1) birds like the fruit and spread the seeds; and 2) the leaves are toxic to most species. Lantanas, especially the unripe berries, contain pentacylic triterpenoids that cause liver problems and phototoxicity in grazing animals (including small children).

Digitals spp. Image credit: Salt Spring Community

Foxgloves are an old garden favorite. The name has an odd etymology that doesn’t actually involve small reddish quadrupeds (Wiki can tell you all about it). Another name for this plant is deadman’s bells. Foxgloves contain cardiac glycosides and have actually been used to treat some heart conditions since the 18th century. My grandmother, who has had congestive heart failure, is on a synthesized form of digoxin. However, cross the [narrow] therapeutic threshold and foxgloves can cause nausea, halos, delirium, irregular heart rhythms, and death. All parts of the plant are toxic, not just for humans, but also for dogs and cats. Even drinking the water that cut foxgloves are sitting in can be deadly.

Conium maculatum. Image credit: jkirkhart35

I doubt anyone plants poison hemlock on purpose, but it’s a common weed in fields and pastures. It’s quite a delicate looking plant, a spindly 6′ tall with dainty little white flowers. Purple spots or streaking on the stalks are a dead giveaway, but it resembles plants that are edible or medicinal (Queen Anne’s Lace, wild fennel, parsley. Socrates is probably hemlock’s most famous victim. Hemlock contains a highly toxic compound called coniine, which paralyzes the muscles, including the heart. It doesn’t take much to cause death — 100mg of the leaves, root, or seeds.

There are many, many others: nightshades, sago palms, castor bean, angel’s trumpets, water hemlock (as if one deadly hemlock weren’t enough), buttercups, dieffenbachias…just more proof that nature’s chemicals aren’t necessarily safer than manmade ones. Which poisonous plants do you have in your garden? 

OK, I think I’m done poking my naturalistic fallacy in the eye with a sharp stick now. If you’re interested in the topic, you might enjoy:

31 responses to this post.

  1. I grew up with oleanders all around my neighborhood and a castor bean tree in our garden. I was and still am intrigued by the beauty of the inner seeds that come from within the spiny castor bean pods once they dry up. The are really beautiful: And supposedly, as few as six or so of them ground up and swallowed will cause cardiac arrest.


    • Hi Donn,

      They are lovely. I never noticed the swirly patterns before. Castor beans cause death less often than you might think given the toxicity of ricin; swallowed whole, they tend to pass through the digestive system undisturbed. Still, probably a good thing they weren’t in our garden when I was growing up!


  2. Posted by EcoCatLady on 06/07/2012 at 23:45

    Eee Gads! I actually have no idea what most of the ornamental plants in my garden even are. I tend to practice “Darwinian gardening” when in comes to non-food things… so if it can survive with the scant water and care that I’m willing to give it, it will thrive and multiply – otherwise, not so much.

    Let’s see… there are marigolds, dianthus, a zillion varieties of sedum, iris, tulips, daffodils, grape hyacinth, roses, creeping bell flowers, hens & chicks, lily of the valley, day lilies, clematis, sweet alyssum, lavender, candytuft… hmmm… perhaps I have a better idea of what’s out there than I think! Is any of that deadly? I know that lilies are poisonous to cats.

    Oh and then there’s the weeds… lots and LOTS of weeds! Thistles, dandelions, milkweeds, and the bane of my existence… bindweed! Actually, if it turned out that bindweed was edible I think I could single-handedly solve world hunger! Will any of that kill me? Not that I intend to eat any of it… just curious.

    OK, I’m rambling again, sorry. Have you ever seen the movie “White Oleander”? I never understood the title before now. And is that second one – the “lantanas” the same thing that’s sometimes called “butterfly bush?” I think they plant those at my local park… yikes!


    • Hi Cat!

      Let’s see…lily of the valley is pretty toxic (especially the berries). That’s the only one I know of from your list, but I don’t recognize all the flowers on it. From a quick review of Wiki (I know, I know…I should look at a real botanical resource!), you should be OK. Butterfly bush appears to be something different (and not toxic).

      Have you ever looked into eating wild plants? I wonder if you could get some tasty salads out of your weeds! Quite a few common weeds are edible in some form or another. Off the top of my head, there’s purslane, clover, miner’s lettuce, some thistles, dandelion leaves (pick ’em before they flower, otherwise they can be bitter), stinging nettles (pick with care!). I have a copy of Samuel Thayer’s Edible Harvest, but alas, most of the plants don’t seem to be common in California.

      I haven’t seen White Oleander, but I think the cover of the movie may have been how I first started to identify oleanders around me. Worth seeing?


      • Posted by EcoCatLady on 06/08/2012 at 11:33

        Thanks for the info on the lily of the valley! I fear I am deathly allergic to almost everything in the dandelion family, so I won’t be eating any of those. I also just don’t think I’m brave enough to try foraging in general. Given my allergic history, it sorta seems like a bad idea.

        I’m not sure if I’d recommend White Oleander or not. Sorta depends on what you’re into. It’s a fairly dark film about a girl surviving a horrific childhood. I tend to enjoy that genre because it makes me feel like I got off easy all things considered!


        • Oh yeah…forgot about your allergies. 😦 Allergies take the fun out of everything, especially adventurous eating! I haven’t done much foraging, either. I’m a lot less brave (or a lot less stupid) than I was as a little kid.


    • The flowers of marigolds, tulips, roses, day lilies and lavender are all edible, but you have to be careful not to confuse day lilies with other kinds of lilies that are toxic. I’ve been wondering about bindweed, too, so I looked it up. The answer is mixed – yes it can be eaten, but it’s purgative.
      Not sure whether to try that one or not!


      • Posted by EcoCatLady on 06/08/2012 at 11:35

        I’m leaving the foraging to the brave souls like you! And I’m definitely passing on the bindweed! I’ve heard that goats love the stuff though. Maybe I just need to borrow a small herd for a few days or something!


      • Posted by Rosa on 06/11/2012 at 19:20

        daylilies are pretty distinct (I have day & asiatic lilies) and the daylily buds are delicious deepfried. Too many raw stalks in your salad is hard to digest even if they’re technically edible, though.


  3. Posted by Shirley Goode on 06/08/2012 at 07:59

    This was worth reading and passing on. Your discriptions were very well done and helpful. Thank you! Shirley, Portland, OR


  4. Posted by Shirley Goode on 06/08/2012 at 08:15

    Check out ALAN BRADLEY’ S books…..the protagonist was YOU as a child! Portland, again


    • Oh, nice! I just checked out his Flavia books on Amazon and they sound exactly up my alley. Thank you for the recommendation. I treated my mom’s garden like a cross between a salad bar and a chemistry lab…have since realized that a number of things I tasted were mildly toxic (rattlesnake weed, whose sticky white sap I used as glue, four o’clocks whose seeds I ground up into powder). I think my mom probably could have taught me to be more cautious, but I’m not sorry that plants were such a big part of my childhood.


  5. The Duchess of Northumberland shares your fascination with poisonous plants:

    She’s not so free with information, though, you have to actually visit her garden to learn about the plants.


    • Hi Rachel,

      You know what? I *just* missed the poison garden when I went up to Alnwick in, what, 2004? They were in the process of setting it up, and I left the UK before they finished. I was keenly disappointed to have missed it. I forgot about it when I was back in Durham two years ago. I’ll probably be back in Durham in another couple years and will have to make a point of going back to Alnwick.


      • I went there a few years ago and just missed the poison garden tours because my timing’s so rubbish that I turned up late… twice. The second time I followed round on the path above to hear what I could from there. The guide didn’t look very impressed!


  6. Loved “Wicked Plants” by Amy Stewart! And her “Wicked Bugs” is great too.

    We’ve got tons of oleander and lantana, plus a number of sago palms. They’re all pretty standard desert landscaping, very drought-tolerant. We’ve got a bunch of pencil trees (Euphorbia tirucalli) that we have to be careful trimming because the white leaky sap is toxic, can cause blindness and skin irritation.

    Oh yeah, and two kids who love to stick things in their mouths. So I’m constantly on the watch.


    • Hi Renee,

      There were some great characters in Wicked Plants! I think you might enjoy the kinda picture book The Poison Diaries — the artist includes one botanical illustration, and one personified one, and they are seriously cool (in a dark, give-my-7-year-old-self-nightmares kinda way). Deborah Blum is also working on a book about poisonous foods. I am really looking forward to that one.

      I was one of those kids and I turned out OK. 🙂 I think my mom kinda figured she didn’t have anything really toxic and I probably wouldn’t eat enough of anything else to make myself seriously ill. Most poisonous things are pretty bitter.


  7. I have always been fascinated by the story of Socrates and the deadly hemlock. What I always find amazing is how ignorant most of us are to the poisonous plants around us. Hydrangea is a very common one in yards everywhere. Not so dangerous as some, but still…

    Then there’s mushrooms. I know, I know, not plants, but the bane of many amateur foragers!


    • Hi Brenna,

      Oh! I didn’t know hydrangeas were moderately toxic. I accidentally killed my mom’s a couple weeks ago when she was away. Those things sure need water…I assume that’s where their name came from!

      I’m actually a lot more wary of mushrooms than I am of plants. I feel like I basically know all the really toxic plants (everything else I’d have to stuff down like a salad to inflict serious damage), but many poisonous mushrooms look similar to edible ones. I can identify a mushroom in the amanita family, the one that includes the death cap, but there are others that can make you pretty sick from lots of different families.


  8. Now see, Jennifer–the whole reason you survived your youth was because even then you were practicing moderation. Moderate consumption of iffy plants=failure to croak. Happy day!


    • Hi R. K.,

      How right you are! Maybe I didn’t give my younger self enough credit. 🙂 If it was bitter, I stopped at a lick. (Apparently the lick test doesn’t work with mushrooms — death caps are said by survivors to have been delicious!)


  9. Posted by San Diego Plumber on 06/30/2012 at 00:41

    Wow! Who would’ve thought, right? All along when somebody mentions poisonous plants and flowers, the first thing that comes to my mind are the venus fly traps or the pitcher plants. It seems I need to know more about the delicate-looking plants.


  10. […] to overcome my naturalistic fallacy and look at plants in a more rational way. Some can heal, many can harm, and a fair number can kill. If you’re not convinced that plants have a dark side, think […]


  11. […] taken you on a number of virtual nature walks (woods, trees, poisonous plants), but now I’d like to introduce you to the most common and least loved plants of all: weeds. […]


  12. This might be belated as far as time standards go, but I would be curious to talk to anyone with more expertise on this subject. I recently returned from a year long stay in Peru, and have become fascinated with arrow poisons, which just augments my preexisting interest in poisons and venoms. Does anyone have ideas on how to turn any of the backyard poisons into pastes or powders that can be applied to arrows, blowgun darts, that sort of thing? My first assumption would be to produce the substance and mix it with some type of adhesive reagent. But my issue is that I don’t want to cause too much diluting. Not to mention, I don’t have many ways of testing… Unless I have volunteers?


  13. […] taken you on a number of virtual nature walks (woods, trees, poisonous plants), but now I’d like to introduce you to the most common and least loved plants of all: weeds. […]


  14. […] to overcome my naturalistic fallacy and look at plants in a more rational way. Some can heal, many can harm, and a fair number can kill. If you’re not convinced that plants have a dark side, think […]


  15. Posted by Celeste Underwood on 07/20/2013 at 13:58

    can toxic plants cross pollinate to non-toxic plants? I have some butterfly weed that is growing right next to some fig plants, ready with figs. Can these figs be eaten safely? There is also an angel trumpet in that same garden.


  16. […] taken you on a quantity of virtual nature walks (woods, trees, poisonous plants), but now I&#8217d like to introduce you to the most widespread and least loved plants of all: […]


  17. Posted by mary h on 04/15/2020 at 04:26

    When I was in Maui I put the teeniest bite of a white mushroom in my mouth. Immediately I began salivating. I spit it out but it took awhile before I felt like I was ok.


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