by Kelly Ann Butterbaugh

 

            While listing the possible dangers of a backyard things come to mind such as insect bites, splinters, and a few untamed animals, but do tomatoes make the list of things to fear?  In 1600s America the tomato, then called the “love apple,” was considered to be a poisonous fruit because of the odor of its leaves.  In other parts of the world it is rumored that the fruit itself was poisonous.  Today it is known that the tomato plant does contain the chemical tomatine which can cause digestive distress; however, the chemical is concentrated in the leaves and stems with little in the fruit.  Extensive amounts of the plant would need to be eaten before causing any reaction, but gardeners do notice the skin reaction caused by handling the plants.

            While the tomato may not be the most poisonous of plants, according to the 2004 Annual Report of the Toxic Exposure Surveillance System 74,811 cases of possible poisoning by plant exposure were reported.  The same report states that plant cases make up 3.1% of all the poison exposures during that year, putting plants at number eleven in the list of common causes of poisoning.  A similar TESS report from 1998 lists 84,185 cases of possible plant poisoning in children under the age of six, 3,294 needing treatment at health care facilities.

            How then do we peaceably live with these flora?  Much like living with a dog, we must learn to avoid the dangerous aspects of these plants.  We know not to tease a dog when he’s eating for fear of being bitten, so now we must learn to avoid the toxic parts of the plants as well.

 

The Top Three

            While many plants like the tomato pose a minimal threat to humans, some pose a more serious threat.  What plants then pose the largest threat of all?  Toxicology experts agree that the most poisonous plants are the castor bean, ricinus communis; the rosary pea, abrus precatorius; and the water hemlock, cicuta spp. 

How fatal are these plants?  One rosary pea or castor bean seed can be fatal to a human.  Meanwhile, death from the ingestion of the water hemlock can occur within two hours. 

Both the castor bean and rosary pea contain lectins, forms of protein, which make them fatal if ingested, injected, or inhaled.  The plants isolate their poisons in their seeds, making them safe otherwise.  The castor bean’s lectin is known as ricin, while the rosary pea contains abrin, a chemical cousin.  Ricin causes respiratory failure if breathed and kidney, liver, or spleen failure if ingested.  Even dermal or ocular exposure causes redness and irritation.  If untreated, ricin exposure is fatal within 72 hours. 

            Meanwhile, the water hemlock is a bit more of a problem since the entire plant contains cicutoxin.  Citutoxin affects the central nervous system and causes nausea and abdominal pain within an hour of ingestion.  Being a close relative to the carrot family, the water hemlock, also known as cow bane, is often mistaken for caraway.

To list all of the poisonous plants is a tedious task both to write and to read.  Yet, many contain three types of poisonous chemicals:  oxalates, glycosides, and alkaloids. 

 

Oxilates           

            Oxilates damage the digestive system because of their needle-like shape as they pass through it, causing severe burning sensations in the mouth and throat as well as swelling.  Eventually the chemicals damage the digestive tract, leaving permanent liver and kidney damage if the poisoning is severe enough. 

 

Jack in the Pulpit, Arisaema spp.

            A plant found in wooded areas, the green stem forms a cup-like flower under the leaves, giving it its namesake.  All parts of this plant are poisonous since they all contain an oxalate.  Ingestion should be avoided as well as the handling of broken plants which can transfer some of the oxalate to the mouth. 

 

Arum family, including philodendrons, dieffenbachia, and rhubarb

            As many as 2,421 children under the age of six in the US ingested philodendrons in one year.  Arums are known for their showy and attractive leaves, making them ideal houseplants.  All of them contain oxalates as well as anthraquinones which are fatal in large amounts.  However, some arums like rhubarb are kept outside.  While the red stems of the rhubarb plant are tasty and safe, the toxin lies in the green leaves which should not be prepared with the stems but removed first.  While reports show philodendrons causing only minor sickness, cases involving poisoning by rhubarb show more serious illnesses.

 

Alkaloids

            Alkaloids are prevalent in plants, finding their way into at least 40% of all plants.  While they can be medicinal, some cause fatalities by altering the heart’s functions.  Most cases of ingestion cause mild to severe digestive disorders.

 

Bleeding Hearts aka Dutchman’s Breeches, Dicentra spp.

            Dainty in both foliage and flower, these plants are a problem if they enter the body.  Tainted with isoquinoline alkaloids, they are poisonous in large amounts.  Avoid ingestion.  Skin contact causes irritation, and burning of the plants should be avoided due to eye irritation. 

 

Delphiniums and Larkspurs, Delphinium spp.

            Also containing alkaloids are the tall members of this family.  With delphinine and ajacine present in all parts of the plant, they have been known to be fatal in some cases of ingestion.

 

Yew, Taxus cuspidata

            While the yew contains alkaloids, it also contains taxine which is a fatal poison.  The poison is most prevalent in the leaves of this evergreen with red berries that look almost fake.  Unfortunately, the fatal poisons found in the yew produce few warning signs and often go undetected.  While the pulp of the berries is harmless, the seeds inside them contain the poison and should be avoided.  Notably, bark extracts from the yew plant have been used recently in cancer treatments.

 

Glycosides

            These compounds are not harmful until they undergo digestion.  In the digestive system the sugars attached to these chemical compounds are removed, turning them into poisons in the body.  Found in plants such as aloes, roses, and horse chestnuts, they are also found in many of the same plants containing alkaloids.

 

Foxglove, Digitalis purpurea

            This plant is both a bane and a blessing.  While the cardiac and steroid glycosides contained in its seeds are poisonous, they are also used to create the life saving heart medication, Digitalis.  Logically, large doses of the plant cause an irregular heartbeat and pulse.  These plants form tall stems lined with delicate bell-shaped flowers but only bloom in alternating years. 

 

Sweet Pea, Lathyrus spp.

            More serious is the ingestion of the sweet pea seeds.  Containing phenol and glycoside as well as other poisonous chemicals, permanent paralysis, a slow pulse, and weak breathing are the results of the digestion of these seeds.  The sweet pea crawls along the ground or trails up trees and polls, suspending vibrant pink flowers from its stems. 

 

Oleander, Nerium oleander

            In 1998 there were 785 reported cases of children under six ingesting oleander.  All parts of this plant contain a variety of poisons including saponins and cardiac glycosides.  Upsetting the heart as well as the digestive system, this plant is listed as “extremely poisonous.”

 

            While the toxins in these plants may make one afraid to leave the house, it should be noted that no fatalities in children or adults due to plant toxins were cited in TESS’s latest reports.  Of the reported 84,185 plant exposures in children only 13 resulted in major health effects.  Instead of fearing these plants, respect their poisonous powers and recognize the hidden dangers of the often beautiful flora.

            For more information as well as a comprehensive listing of poisonous plants in the US see Cornel University’s web page at  http://www.ansci.cornell.edu/plants/