Smith’s brief description neatly summarizes the plant’s appearance and irritant effects: “The poisoned weed is much in shape like our English Ivy, but being but touched, causeth rednesse, itching, and lastly blisters.”īoth men, however, went on to defend the plant. In 1624 explorer John Smith published the first written account of poison ivy, basing it on an unpublished manuscript by Nathaniel Butler, who learned about the plant while governor of Bermuda. These vines, shrubs, and trees have been collected as exotic garden curiosities, have been sourced for medicine that might cure rather than harm, and have been harvested for the sticky sap that gives lacquerware its sheen. Over the centuries intrepid botanists, daring physicians, master craftsmen, and persistent chemists have looked for the good side of poisonous plants. But as Bartram’s packing list suggests, there is more to these plants than the painful, itchy rashes they cause. The common three-leaved plant and its relatives-poison oak and poison sumac, found in North America, and the lacquer tree, native to Asia-all contain urushiol, an organic compound that sets off violent allergic reactions in most humans. For most people poison ivy has long meant just one thing: suffering. It may seem incredible that Bartram offered these noxious plants for sale and that people in Europe actually bought them. Numbers 114 and 120 on the list, bracketing 5 varieties of grapes, were a bit different: “ Rhus vernix” and “ Rhus radicans,” known to us today as poison sumac and poison ivy. Bartram’s shipment included 12 oak species, 9 different pines, and 3 kinds of plums, along with such flowering plants as sunflowers and morning glories. European collectors were eager to buy New World trees and plants, whether useful, ornamental, or simply unusual. He was packing up seeds and young plants to send across the Atlantic, as he had many times before. One October day in 1784 Philadelphia horticulturalist William Bartram wrote out a list of 220 “American Trees, Shrubs, & herbs” in his fine, flowing handwriting. negundo, Toxicodendron rydbergii, Western Poison Ivy by admin. This entry was posted in Michigan Shrubs, Uncategorized and tagged Anacardiaceae, Eastern Poison Ivy, Michigan Poison Ivy, Rydberg's Poison Ivy, Toxicodendron radicans, Toxicodendron radicans ssp. Caution: These remarks concern Poison Ivy in Michigan, the species vary more outside of the state. I posted this more to illustrate the range of variation in Poison Ivy in Michigan and to explain why it looks different in the northern or southern parts of the state. Look at a number of characters before deciding which species you are dealing with. However, please note the number of times I wrote “normally” when contrasting these two species. The two species are normally quite distinct. They are intermediate between the two species.
Hybrids between Eastern and Western Poison Ivy are known and occur along the band where the two species overlap. Atlantic poison oak ( Toxicodendron pubescens) grows in the southeastern United States. Western or Pacific Poison Oak ( Toxicodendron diversilobum) occurs along the west coast of the United States. Eight species grow wild in Michigan, seven are native.Īlthough nothing controls common names, the name Poison Oak is best used for species that do not occur in Michigan. They include the Cashew, Pistachio, and Mango. Most of the family’s 800 species are tropical. Poison Ivy is in the Anacardiaceae (Cashew or Sumac family). See blog post for winter twig terminology. The urushiol oil is present in all parts of the plant including the bark and buds so you are not safe from poison ivy in the winter. If it is Eastern Poison Ivy then it will normally climb and have aerial rootlets without tendrils. The twigs have many lenticels (dots on twigs) and their pattern is distinct but difficult to describe. Twigs are normally gray but can also have a reddish (or even a greenish) tint. The terminal buds end in an abrupt point.
Poison Ivy in the winter is recognized by its hairy, grayish, lateral buds with half-rounded or shield shaped leaf scars.