Edible and Harmful Plants
Lists and Resources
©1994, 2001 Melissa Kaplan
If you have not read through the information on this page before, please take the time to do so. While you may not need all this information right now, at least you will know where to find it in the future.
The combined lists and resources have been combined into a single 47-page document that is available for download and printing in PDF format.
you need to be concerned about plants
An animal in its native environment knows what it can and cannot eat. If it makes a mistake and becomes ill, it will not eat that plant again. If it eats a plant that kills it, well, it clearly won't be eating it again! The fact that the leading cause of death of herbivores and omnivores in the wild is not from eating toxic plants indicates that animals either learn their lessons well by observing older conspecifics or by being born or hatched with a sort of genetic field guide to edible plants.
Once you remove an animal from its environment, however, that field guide and learned avoidance becomes useless. Instead, the animal will pretty much try to eat anything that resembles what it is programmed (learned or instinct) to eat. Hence, toxic plants such as azaleas and oleanders look like a terrific snack for a hungry or curious iguana or tortoise.
If you are thinking about furnishing a tank with plants, or are considering letting any of your herbivores or omnivores free-roam in your house or in an outdoor enclosure, you need to assure that the plants in those areas are not toxic.
The toxic chemicals of plants are passed to an animal in one of two ways - by ingestion of plant material or by superficial physical contact with a plant or certain parts of the plant. If anyone has ever had poison oak or ivy, they are quite familiar with this latter method of transmission. Some plants are completely toxic; others have only certain parts that are toxic, such as the leaves, or flowers, or roots/rhizomes, or seeds. Some plants contain toxins strong enough to kill the animal, others will make them seriously ill and may lead to death. Others may just make them wish they were dead. With other plants, the toxic effect may depend on how much is ingested, the size of the animal ingesting it, and/or it's relative health or what else it has eaten that day.
Some plants can cause injury in other ways, such as lacerating or puncturing the body, eyes, mouth, etc. They may cause ulcers, lesions and abscesses on the skin, and intestinal impaction from indigestible plant parts. Kale, for example, has very hard ribs and veins that, when torn and offered still attached to the leafy matter, may scratch or puncture a lizard or tortoise's throat or esophagus as, rather than chewing their food, most herbivorous and omnivorous reptiles just tear or rip and swallow their food. Another example is thorns on cactus and other plants that are placed in an enclosure, or an impaction of fig seeds in a hatchling's gut.
Examples of plants with nonlethal but nonetheless potentially harmful chemicals include bok choy, broccoli, Brussels sprouts, cabbage, and soy, which contain goitrogenic compounds. These chemicals bind iodine, preventing its uptake, thus leading to impairment of thyroid gland function, which in turn leads to a host of metabolic problems. Spinach, parsley, carrots, and chards contain calcium oxalate, which interferes with calcium uptake; when fed as a significant portion of the overall diet, they cause the mineralization (hardening, crystallization) of organs and muscle tissue and can bind enough calcium to cause a form of metabolic bone disease.
Some of the plants that appear on lists of foods recommended for your reptile are also on the Harmful and Toxic Plants listing. Does this mean you should stop feeding them? No. It does mean that you need to make sure to alternate these plants with others known to be safely edible to ensure that your reptile is not getting significant amounts of the problematic phytates. Some may be okay for occasional treats, such as bok choy or a little bit of soy. A couple of leaves of spinach now and then won't hurt, either. But feeding these foods on a regular basis (say, no more than a small amount a couple times a month or every other month) will be safe and provide some variety in the diet.
Does this mean that you can then feed, or not worry about, your reptile eating other plants on this list? No. While an iguana may get away with eating a bite or two of poinsettia, it won't get away with eating a similar amount of azalea. The rule of thumb I follow is: if it isn't on a recommended food list I trust, I will not be feeding it, nor will I allow my reptiles access to it.
Those of us with part- or full-time free roamers face special problems. No matter how closely we watch our reptiles when they are out, we can't watch them 24 hours a day, seven days a week. Your iguana may ignore that English ivy or creeping charlie or rubber plant for years, but that doesn't mean that some day, when he is feeling a bit bored, or peckish, or is just ticked off at you for going away on vacation, he won't try a leaf or two. And that may be all it takes for you to end up with one less iguana.
I used to have some bonsai I was working on, as well as some pots of pothos and wandering jew. Well, despite the fact that the wandering Jew (Zebrina spp. or Tradescantia zebrina) was a plant my iguanas could safely eat*, did they try to eat it? Of course not. They went for the pothos and the bonsais The pothos were also safe to eat in small quantities, but not the species I was bonsai'ing. I finally realized that it was best if I didn't keep any plants in any room that was not closed off to the iguanas. Since they have the run of the house, that means no plants. Even closing a room off isn't a guarantee. Family and guests sometimes forget to close doors, and I know at least one person whose iguana managed to get, unnoticed, into a "closed" room and ingest part of a poinsettia before being discovered.
*It should be noted that some Tradescantia sp. appear on toxic lists, others on edible lists. In the UC Davis toxic list, which lists common name Wandering Jew for Tradescantia sp., they have the notation that this plant may cause dermatitis from coming into contact with it. The Plants for a Future Database, which lists many plants useful for food, fiber, shelter, and medicinal uses, lists only one of the Tradescantia species with edible leaves and flowers, the Tradescantia virginiana (Virginia spiderwort), which has several other synonyms for its scientific name (T. virginica, T. virginica, Ephemerum congestum, T. brevicaulis, T. congesta; T. rupestris, T. speciosa, T. virginiana var. alba, T. virginiana var. barbata). What this means is that you should check several sources and then make the best decision you can as to whether you will put the plant in an area accessible to your reptiles (or human children). It also points out why writing me in frustration asking me for a definitive answer because you can't find a definitive answer to a plant that isn't as outright toxic as oleander or azalea won't accomplish anything but frustrate us both. So, when in doubt, leave it out.
Before there were as many good plant resources on the web, I started compiling my own lists of Toxic and Harmful Plants.
One source for identifying weeds and finding out if they are safe or not is to get one of the many field guides to edible plants such as Thomas S. Elias and Peter A. Dykeman's Edible Wild Plants: A North American Field Guide (Sterling Publishing Co., Inc., New York, NY. 266 p. ISBN 0-8069-7488-5). Other resources are discussed below.
If there are no signs, continue to observe for 24-48 hours. You may wish to contact your vet the next business day even if there are still no signs in case there is anything she or he wants you do to.
Useful Plant Websites
The U.S. Food & Drug Administration's Center for Food Safety & Nutrition also has a Poisonous Plant List.
Plants for a Future is a listing of edible and otherwise usable plants.
I've not fully explored this site but it does seem to have pictures of the plants and is accessed by common or scientific name. It is part of the University of Illinois' Toxic Plants for Animals database for its veterinary students. The U of I is where the Animal Poison Control Center (APCC) is located.
The University of California, Davis, also has an extensive site of safe and toxic plants (be sure to scroll down to the bottom of their page for the link to the toxic database).
The USDA's Agricultural Research Service's Phytochemical & Ethnobotanical Database doesn't have all plants, and won't provide lists of toxic or safe plants, but you can look up many plants to find out what chemicals they have, or look up chemicals and see which plants have them.
The Guide to Plant Relationships is actually an informal guide for people who have allergies to one type of plant to find out what related plants they may need to avoid. It comes in handy now and then for herpers researching plant-related information.
The USDA's Searchable Nutrient Database lists the basics - water, kcal, protein, fat, carbs, vitamins, and minerals for plant foods. The listings are only for foods commonly eaten by humans (so you will not find things like hibiscus flowers on it) and does not include information on potentially harmful chemicals/compounds such as calcium oxalates. (Other nutrient databases...)
Finally, I strongly recommend the use of a meta-search engine in which you can search for exact phrases as well as indicate "AND" and "OR" using Boolean or other operators.
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© 1994-2013 Melissa Kaplan or as otherwise noted by other authors of articles on this site