Toxicodendron radicans [ Plantae: Angiosperms: Eudicots: Rosids: Sapindales: Anacardiaceae: Toxicodendron: Toxicodendron radicans ]
Poison Ivy grows throughout North America, in the United States and through Quebec, Ontario, and Manitoba of Canada as well as the mountainous regions of Mexico.
Its similar species, poison oak – Toxicodendron rydbergii is found in the western United States.
Poison Ivy is a dioecious poisonous North American plant growing either as a trailing vine (upwards of 10-25 cm), a shrub (upwards of 1.2 meters), or as a climbing vine growing on trees. It is an understory plant in the forest. This vine has reddish hairs that are like leaves, that branch off light to dark green leaves that turn bright red in the fall. Leaflets of mature leaves are shiny ranging from 3-12 cm long, but rarely upwards of 30 cm in length, each leaflet has few to no teeth along its edges and hosting a smooth surface, clustering alternate on the vine that produces numerous aerial rootlets as well as adventitious roots that can spread from rhizomes or root crowns. It blossoms inconspicuous yellowish or greenish white flowers bundled in clusters up to 8 cm above the leaves from May to July. Flowers fruit into berry-like drupes that mature from August to November with a greyish white color feeding many birds and animals that disperse the seeds in their droppings.
Is found in wooded areas along plant edge areas, in exposed rocky areas, open fields, and disturbed areas. It is shade tolerant. It is not sensitive to soil moisture but does not grow in deserts or arid conditions. It can habitate a wide variety of soil types, as well as areas subject to seasonal flooding, or brackish water.
Poison Ivy produces urushiol, a clear liquid in the sap that causes an itching rash to those who encounter it. It creates a reaction that is urushiol-induced to cause dermatitis that 70-85% of the human population allergically reacts to that can progres to anaphylaxis. Poison Ivy attacks upwards of 350,000 people a year. If the plant is burned and the smoke inhaled, it will cause a rash on the lungs causing pain and possible fatal respiratory issues; If eaten it will damage the mouth and digestive tract. The rash can lasts 1-4 weeks depending on severity and treatment. Its oil can stay active for several years, so handling dead leaves and vines, exposed gloves or clothes, can cause a reaction.
Folklore and History: “Leaves of three, let it be”; “Raggy rope, don’t be a dope”; “One, two, three? don’t touch me!”; “Berries white, run in fright”; “Berries white danger in sight”; “LOnger middle stem, stay away from them”; “Red leaflets in the spring, it’s a dangerous thing”; “Side leaflets like mitens, will itch like the dickens”; “If butterflies land there, don’t put your hand there”; and “If it’s got hair, it won’t be fair”; are folk rhymes to teach children to avoid the plant.