Is What They Say About Plants With
Calcium Oxalate Crystals True?

Sometimes found incorrectly as Calcium oxylalate

If you eat part of a Philodendron will you die?
Do Tropical Aroids and Philodendron species contain the Poison websites claim? 
Or is it just a bit of "internet truth" that isn't really true?  Did they tell you this "poison" is in spinach?
If you are a vegetarian you probably shouldn't read this!

If  you type the word "Philodendron" into almost any internet search engine many of the top sites that pop up will immediately warn you the plant is a "poisonous house plant"!  Some will tell you the plants shouldn't even be in your home.  Yet Philodendron species are among the most popular of all house plants.  How can it be possible some of the most "poisonous plants" end up as the most popular plants?  Is the claim Philodendron sp, Anthurium sp. Colocasia sp., Alocasia sp. and other aroids are poisonous really true?  Perhaps we need to dig just a little deeper.  

Is it a good idea to eat the leaves of a Philodendron, an Anthurium, Colocasia or other member of the aroid group of plants?  In most cases, probably not!  But in some instances, you've probably been served an aroid and never knew you were eating one!  Ever been to South America, Central America, the South Pacific, Hawaii or the Caribbean?  Some of these plants are eaten daily as a staple diet!

I prefer to do my plant research in botanical journals.  I often avoid the internet for several reasons.  One principal reason is anyone can say anything on the net and there is no resource or "net cop" to verify it is true!  You can post information that is absolutely false, yet there it sits for anyone to read  and accept as absolute truth.  It used to be said "people always believe what they read in the newspaper".  Now it appears people will believe almost anything they read on the internet.  Perhaps that's why you get so many junk emails claiming canola oil will kill you!  Or the mail in your snail mail box can give you AIDS.  Or it's dangerous to pump gas because of hidden needles.  Or Saran Wrap™ will cause cancer!  People tend to believe what they read.  And that is especially true with information regarding plants!  Unfortunately, there is simply a lot of bad information on the internet.  But this one does contain at least "some" truth.

Almost every time I elect to type the name of a plant, especially a Philodendron, into a search engine more than a dozen websites will warn me the plant contains calcium oxalate crystals and is a "deadly poison"!  They claim the plants will kill my children, birds, cats, dogs, rabbits and almost any other critter I allow to touch them!  Especially if someone or some thing takes a bite of one.  I've written and published hundreds of magazine articles.  About a year ago I wrote an article questioning if it was wise to allow tropical birds to fly free in a tropical atrium like our Exotic Rainforest.  One magazine editor went ballistic.  She felt allowing birds to fly anywhere plants could be found was extremely dangerous because the bird might eat a plant!  I agree!  It is more dangerous for the plant, not the bird!  Do you have any idea where tropical birds normally live?  Do you know what grows on almost every jungle tree where they live?  Philodendron species, Anthurium species and others that are closely related!  And by the way, our birds don't fly free!

Sites that are created to offer mothers information to protect their children, as well as pet websites, pass along the information regarding calcium oxalate crystals all the time almost always saying Philodendron sp. are poisonous.  For some odd reason many people believe your Philodendron plants truly are a deadly danger and keep passing that information along! That's probably why you are reading this now.  Someone or some site has warned you about the danger posed by your plants.  But the fact is that bit of information is simply not completely scientifically accurate.  And you can easily find many scientific textbooks, and some websites, which will explain why the warning is just not completely correct.  All you have to do is do your homework.  If you look at the best texts or sites you'll quickly discover the problems they describe are "symptomatic".  That is not defined as "deadly".  A good dictionary will tell you "symptomatic" is defined as something similar to: "Symptomatic treatment is the practice of treating a patient's symptoms, rather than the disease or injury itself."  So what does that actually mean?

Philodendron sp, Anthurium sp, Alocasia sp, Colocasia sp. and other members of the aroid family normally taste bad if you try to eat one!  So just don't eat one!  Unless of course you are going on vacation to Hawaii!  In that case, I promise, you'll eat one!  In rare cases they can cause serious complications if ingested.  But if you read all the hype posted on internet sites you'll believe they can kill you!  That is both rare, and a long term result of eating them in excess.  As a result you are told you are not supposed to grow them in your home if you have children.  Or cats.  Or rabbits. 

They truly do contain the chemical substance known to science as calcium oxalate crystals.  If eaten, the leaves may possibly cause burning, swelling, and rarely choking.  They will certainly burn your mouth if chewed in large enough quantity and can make the tissues of the mouth swell.  But it is much more involved than what those sites would have you believe!  The oxalate crystals alone may not be the culprit!  You have only been told part of the story.  A partial truth!  The fact is, only 2 percent of all reported cases of "plant poisoning" require hospitalization. In real numbers, fewer than 500 cases end in a hospital each year.  Still, if you grow these species, you need to know the facts.  And the fact is, few, if any, members of the aroid family are capable of doing the damage some sites wish you to believe if the person who ate them took only a single bite.

Plants that are aroids all contain calcium oxalate crystals.  But so do many other plants that are commonly eaten and not used as ornamental species.  What creates the problem often referred to as a "poison" are the types of calcium oxalate crystals contained in various species.  In Hawaii, a popular native food is known as Kalo.  Kalo is made by cooking a plant known as Colocasia esculenta which you likely know as an "Elephant Ear".  And Kalo contains calcium oxalate crystals in amounts strong enough to be painful if eaten raw.  But if properly prepared, the plant is delicious.  Aroid, palm and cycad expert Leland Miyano who is Hawaiian explains further, "Kalo has two types of calcium oxalate crystals, or idioblasts,....needle-like raphides and club-like druses.  It is believed that the raphides cause the mucous membrane irritations and skin dermatitis.  I can speak from personal experience that eating raw kalo, leaves or corms, is not recommended. It is as if one ate fiberglass.  Another warning is Agave species have these raphides and I can attest to the extreme skin dermatitis from the sap of these...it manifests in intense itching and burning...it is a torture, that can last for many days in some people. In short, although spinach has calcium oxalate crystals, there is no comparison between them.  I eat raw spinach often, but raw kalo, never. Cooked kalo is one of my favorite foods, both leaves and corms.  Poi is the mashed corm and is delicious in my mind. It has been compared to library paste but some luaus cut their poi with flour and it does taste bad. The variety of kalo also determines the taste."

There is one genus in this aroid group that needs to be pointed out before this discussion continues.   That genus is the Dieffenbachia.   Dieffenbachia has an unusually strong form of calcium oxalate crystals combined with other compounds which make it very unpleasant to taste!  Don't taste it!  It can literally make you loose the ability to talk and is quite painful. That is why it is called "Dumb Cane".   At least one confirmed death has been documented.  But the effects of that genus are quite unique due to the combination of chemical compounds.  Read further and you will begin to understand the differences.  Dieffenbachia is a relative of the Philodendron, but it is not a Philodendron species. 

You can turn me in for "child abuse" if you want, but my grandchildren all visit my atrium regularly.  And it is full of rare Philodendron, Alocasia, Colocasia, Anthurium and other species along with lizards, frogs, crickets, worms and  critters kids love!  Mine all know not to put leaves, of any kind, or frogs and worms for that matter, in their mouths!  I'm all for taking good care of pet dogs, pet cats and even pet rabbits.  And I'm certainly all for taking care of my grandkids.  But we've got a pretty simple rule around our house.  And that rule is "don't put the plants in your mouth"!  Most of them taste bad.  That's really all the kids need to know to leave them alone.  

Perhaps, just perhaps, if you ate enough of some of these plants they could be bad for your health.  Perhaps.  Interestingly a common vegetable women love to try to force their kids to eat, since "it's good for them", has the same exact chemical in a high concentration.  Spinach!  Someone better tell Popeye spinach is very high in oxalate crystals and I don't recall hearing of anyone dropping dead or choking recently from eating their spinach!  Well, not counting the recent spinach ecoli scare.  A lot of the same folks who write this stuff on the internet love to add spinach to their salads!  Or make their salads almost totally of spinach!  People often find the taste of spinach to be bad.  Guess why?  They don't like the taste of oxalate crystals.  Some scientists equate it to eating small needles.  It's bitter, and to some, it tastes bad!

I recently did some research on this subject and found this information which is quoted directly from www.eFloras.org, a scientific plant research site.  So you can better understand the discussion, "araceae" is the group of plants that contains most of the plants often condemned as "poisonous".  The www.eFloras.org site says: "Araceae contain crystals of calcium oxalate, which are often cited as causing the intense irritation experienced when handling or consuming the raw plant tissue of many genera in the family. This supposition is contradicted by the fact that although irritation generally is not produced by properly cooked plants, the crystals remain after heating. Other compounds must therefore be involved with causing this reaction. Studies of Dieffenbachia demonstrated that a proteolytic enzyme, as well as other compounds, are responsible for the severe irritation caused by this plant and that raphides of calcium oxalate do not play a major role (J. Arditti and E. Rodriguez 1982). Whether irritation is caused by enzymes or crystals, that aspect of Araceae has resulted in aroid genera being included in many lists of poisonous plants (e.g., K. F. Lampe and M. A. McCann 1985; G. A. Mulligan and D. B. Munro 1990; K. D. Perkins and W. W. Payne 1978)."
 

In Hawaii and other parts of Polynesia the Colocasia plant, known as Black Taro, is used as a food source.  They grow it not as an ornamental, as we do, they grow it to eat!  The leaves, stems and roots are all boiled and eaten.  The entire plant contains oxalate crystals and the leaves are cooked just like spinach, or greens, and used to wrap pork and chicken while it is being cooked in a fire pit. The entire plant contains oxalate crystals just like the supposedly "deadly" Philodendron.  If you totally accept what many pet and children's protection sites on the web would have you believe this plant product should always be called a "deadly poison".  And if you believe that you must also believe it is dangerous to your health to enjoy a Hawaiian feast.  Perhaps someone should explain those plants contain a "deadly poison" to the people of Hawaii and Polynesia!  They eat them all the time, sometimes daily!  Some months ago we cooked some of our Colocasia esculenta for a dinner as a part of a Hawaiian cookout and I'm still alive and well to write this for you to read!   No one got sick.  No one had their mouth burn.   But there may be at least anecdotal evidence eating too much of this plant over a long period of time can cause an increase in kidney stones.

We also love to eat the raw fruit of our Monstera delicosa, as do people from all over the Caribbean.  Monstera species are closely related to Philodendron species.  Look it up!  You'll find many websites claiming "all parts are poisonous" due to the calcium oxalate crystals.  The plant does have it!  But the part about being "deadly poisonous" just isn't so!  We eat it raw and it tastes just like pineapple!  And according to www.eFloras.org cooking the plant has nothing to do with their no longer containing "poison"!  One scientific article says "regular ingestion of "large quantities" of these plants can be dangerous due to their high mineral content".   The important key words are "regular ingestion" and "large quantities"! 

So keep your pets out of the area where you grow your rare and unusual plants and even more important DON'T EAT your tropical plants, or let your kids eat them!  But if you research this topic honestly you'll find these plants are not as dangerous as most internet articles, especially pet sites, would have you believe!  Someone read "part" of a scientific article and took it to an extreme!  They reported only half of the story.

 

I believe personal responsibility is still important.  You shouldn't be able to insist everyone with kids (or rabbits) in the house get rid of their plants or be able to sue someone for what they should have known and done themselves!  Banning every thing that is a possible poison, the way some of these websites rant and rave about Philodendron plants, is not the answer!  Teaching your children about the plants in your possession is still your responsibility.

And, just in case you're a vegetarian, you might want to do some homework on eating your "veggies". Those too may contain a higher concentration of oxalate crystals than you expect.  Dr. James W. Waddick of Kansas City, MO. recently provided this link which I found of great interest:  http://www.vegsource.com/articles/harris_kidney_stones.htm  The information on this site may lead you to learn eating vegetables can have similar less than desirable results for your health and cause kidney stones due to eating an excess of oxalate crystals.  Perhaps all the websites who make overly strong claims regarding oxalate crystals should add we all should stop eating anything with a leaf!  Please don't panic.  I eat more vegetables than meat myself.

 

It is true some plants contain combinations of chemicals that can irritate your mouth and throat if eaten.  A few may cause swelling.  And some people may react violently.  So what is the answer?  Don't chew your collectable plants and  don't eat them!  But I can almost promise if your child takes a bite that will be the last bite!  They taste bad!  How many bad tasting foods can you get your child to eat twice?  They learn quick! 

So how do these tales get all over the internet?  Simple.  One site says it, the next one copies and embellishes it, and it suddenly takes on a life all its own.  The story becomes little more than internet gossip.  So the next time you read something on the internet that raises a doubt in your mind, verify the information in a good scientific text.  Don't instantly believe everything you read about plants on the net.  Check out information posted on any website on a scientific source.  Including this one! 

By the way,  if your child just took a bite of your Philodendron, you might want to consult your physician right now!  Just don't panic.  Chances are, the doctor will simply treat the symptoms.

 

Sometimes I wonder how I ever got past the age of three.  My mother grew Philodendron species all the time!   I must have eaten oxalate crystals at least once! 

By the way, did you know some ferns  and many aroids grow on rocks?  They're called lithophytes.  No kidding.  Check it out!

Want to see some of the rare species we grow?  Click this link.