Poison Ivy

Scientific name:Toxicodendron radicans



Phylum:Magnoliophyta, the Angiosperms (flowering plants)

Class:†† Magnoliopsida, the Dicotyledons

Subclass:Rosidae, the Roses


Family:Anacardiaceae, with cashews, mangos, and pistachios

Genus:Toxicodendron, the poison ivies, oaks, and sumacs

Species:Toxicodendron Radicans | Poison Ivy


Identification:Leaves occur on petioles and are divided into 3 leaflets, which are generally oval in outline.  Leaflets may be toothed, untoothed, or lobed.  Older leaves are generally either toothed and lobed or untoothed and lobed.  The two lateral leaflets occur on very short petioles, while the central leaflet occurs on a much longer petiole.  Although leaf shape is highly variable, the lateral leaflets are often distinctly lobed on one side of the leaflet and not on the other.  Each leaflet is hairless and ranges from 3/4 to 4 inches in length and width.


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Notice the three-part leaves with jagged edges.


Stems:  Woody, climbing on other vegetation or objects or trailing along the ground.  When climbing, poison ivy attaches to other objects by way of aerial roots.  Stems are capable of rooting when they come into contact with the soil.

Roots:   A fibrous root system and stems that root where they come into contact with the ground.

Flowers:  Flowers are small and inconspicuous, yellowish green to green in color.  Flowers occur in clusters of 2 to 6 on stalks that arise from the position between the leaf petioles and stems (leaf axils).

Fruit: A berry, gray to white in color, approximately 5 mm wide.










Reproduction:Reproduces by seed and vegetatively by rhizomes

Sexual reproduction: Numerous, monecious flowers produced in small, dense axillary clusters. Birds and mammals disperse the fruits. Unconsumed fruits are retained on the plant through winter and are dumped beneath parent plant in spring. Exposed mineral soil appears to be favorable to germination and establishment.

Vegetative reproduction: Vegetative growth by rhizome is a major mode of reproduction in traditional plants. Leafy shoots are produced at basal stem nodesalong much branched rhizomes; on some locations, rhizomes may expand up to 7' further than the parent plant. As a result of this general network of rhizomes, Poison Ivy frequently forms thickets under favorable site conditions. These thickets may represent a single clone or several individuals.















        Invades disturbed areas such as roadsides, lakeshores, floodplains, fencerows, logging units, sand dunes, and railroad rights-of-way. Plants rarely dominate large areas but may become locally abundant in mesic sites with moderate amounts of sunlight such as rills, ravines, edges of waterfalls, creek banks, stream bottoms, river terraces, and floodplains.

        Occurs on variety of soils

        In the East typically occupies mesic sites but is also commonly found on rocky fields, pastures, talus slopes, precipices, gypsum cliffs, and slated ledges. A successional species in a variety of plant communities throughout its range.


Region:Most poison ivies are sited in the east of the U.S.















Interesting Facts:Poison Ivy can be mistaken for another plant because they change every season.You have to watch out for the poisonous plant or you will develop allergenic dermatitis, which causes inflammation.Poison Ivy can put you in the hospital if it is not treated.The key is to know what poison ivy looks like so you can avoid it.




LINKS (resources):


The Natural History of the Northwood


Virginia Tech Weed Identification Guide



Madison Hagan


Mr. Fosterís 2nd Biology


March 23, 2003