Most plants in our environment offer many benefits, including beauty, privacy, food, fragrance and medicine. But there are a few plants out there that can prove harmful when inappropriately used or accidentally eaten or touched. Gardeners, particularly those with young children and pets, should familiarize themselves with these potential foes.
Numerous reference books have been written on the subject of toxic plants, including some that have excellent illustrations and/or photographs. However, there may be some conflicting information from one author to another. Stick with books that cite references so that you’ll know the information is based on actual data.
The toxicity of a given plant can vary depending on the plant part, location and time of year, as well as with the victim. Certainly, body weight has a role; generally, the smaller the body, the less of the toxin needed to cause ill effects. This is one reason why children are so vulnerable. An individual’s metabolism also may play a role.
Don’t assume that because a wild animal or bird ate something without becoming sick that it is not poisonous. Different species and even different individuals within a species can react quite differently. Cattle may be killed after eating a particular plant, yet pigs might not show any symptoms at all. Humans might be affected by certain plants, yet dogs or cats may be immune. Poison ivy is a good example of how cats and dogs can run harmlessly through a patch of vines, but people may suffer blistering and itching if their skin comes in contact with the plant’s sap.
Some people may be seriously allergic to certain plants, such as peanuts or strawberries, while others can consume large quantities without harm. Some plants, such as the poinsettia, are often listed as toxic, when in fact studies show that they are not toxic. In the case of the poinsettia, there are individuals who have allergic reactions to the sticky latex sap in the plant.
If you suspect a person or animal has eaten a toxic plant, contact your physician, veterinarian and/or poison control center immediately (Indiana Poison Control Center, 1-800-382-9097). The appropriate action to take will depend on the specific type of toxin involved, so it is very helpful to know the plant’s identity. For cases of animal poisoning, call 1-888-426-4435.
Be prepared by identifying the plants in your house and yard, so that you can avoid potentially dangerous situations or at least be able to act swiftly when accidents do occur. If you have unknown plants, you can get help identifying them from your local university Extension service, garden centers or nurseries. If those sources can’t identify the plant, you can submit samples to the Purdue Plant & Pest Diagnostic Lab (PPDL) for a fee of $11 per sample for Indiana residents. For more information on PPDL services, call (765) 494-7071.
Purdue Extension has a booklet called “Indiana Plants Poisonous to Livestock and Pets” available in printed form through your county Extension office or online at https://mdc.itap.purdue.edu/item.asp?itemID=15946.
There are also several other Web sites that give helpful information on poisonous plants:
University of Illinois: https://guides.library.illinois.edu/plantstoxictoanimals
Colorado State University: https://csuvth.colostate.edu/poisonous_plants/
Cornell University: http://www.ansci.cornell.edu/plants/index.html
Although the number of toxic plants is small compared to the total number of plants in cultivation, the list is far too large to include them all here. However, some of the more commonly grown suspects are listed in the following chart.
Common Poisonous Plants in the Home, Yard, and Garden
Flowers
caladium (all parts)
cardinal flower (all parts)
castor bean (seeds and leaves)
daffodil (all parts)
flowering tobacco {Nicotiana} (leaves and flowers)
four-o-clock (roots and seeds)
foxglove (all parts)
hellebore (all parts)
iris (all parts)
lantana (unripe fruits and leaves)
larkspur {Delpinium} (all parts)
lily of the valley (all parts)
lupine (all parts)
monkshood (all parts)
poppy (all parts except ripe seeds)
snowdrop (bulb)
spurge (milky sap)
star-of-Bethlehem (all parts)
sweet pea (seeds, seedlings, and pods)
tulip (bulbs)
Houseplants
Chinese Evergreen
anthurium (all parts)
aloe (sap if ingested)
calla lily (all parts)
croton (seeds, leaves, and stems)
crown-of-thorns (milky sap)
dieffenbachia (all parts)
elephant ear (all fig (leaves, fruits, and sap)
Jerusalem Cherry (all parts)
mistletoe (all parts)
Philodendron (all parts)
Fruits
apple (bark, leaves, seeds)
pear (bark, leaves, seeds)
apricot (bark, leaves, seeds, pits)
peach (bark, leaves, seeds, pits)
nectarine (bark, leaves, seeds, pits)
plum (bark, leaves, seeds, pits)
cherry (bark, leaves, seeds)
avocado (leaves, unripe fruit, bark, and seeds)
Landscape Plants
azalea (leaves and flowers)
black locust (all parts)
Boston ivy (berries)
boxwood (leaves and twigs)
buckeye (leaves, shoots, bark, flowers, and seeds)
burning bush (all parts)
cherry (leaves, twigs, bark, and seeds)
clematis (leaves)
elderberry (roots, stems, bark, leaves, and unripe fruits)
English ivy (all parts)
golden chaintree {Laburnum} (all parts)
holly (berries and leaves)
horsechestnut (all parts)
hydrangea (leaves and buds of some species)
Kentucky coffee tree (seeds, fruit pulp, leaves, twigs)
oak (acorns, leaves, and young shoots of some species)
poison sumac (all parts)
privet (all parts)
rhododenron (leaves and flowers)
Virginia creeper or woodbine (berries)
yew {Taxus} (all parts except the fleshy red cover on the seed)
wisteria (all parts)
Vegetables
potato (green skin, buds, and sprouts on tubers, also fruits and foliage)
rhubarb (leafy blade, not the leaf stalk)