Mary Anna AndersonOctober Weed - Poison Ivy

Mary Anna Anderson of University of Nebraska Extension, supplies us with information on weeds to watch for each month. Here is a weed to watch for, as even roots and dead leaves can cause problems.

Weed: Toxicodendron radicans  and Toxicodendron rydbergii (formerly Rhus radicans) - Poison Ivy. It is in the cashew (Anacardiaceae) family.

Poison Ivy trifoliate leafDescription: Poison ivy can appear as a shrub or vine. Trifoliate leaflets are attached to a long petiole. Leaflets vary in shape: often each has one or two shallow lobes on the outer side of the leaflet. Sometimes they are deeply lobed, and other times appear almost smooth. The center leaflet has a longer petiole than the lower two leaflets. The petioles with the 3 leaflets on the ends are attached alternately to the twig. The vines form aerial rootlets that cling tightly to trees, fences, and walls. Older vines take on a hairy appearance. In fall the leaves turn a beautiful red and can entice people to pick them for decorations. Flowers are whitish small clusters. The berries are white.

Similar plants: Young boxelder trees are often mistaken for poison ivy as they can have 3 leaflets that look exactly like poison ivy leaves. The difference is that the petiole of the boxelder attaches to the stem opposite another petiole. Some berries such as raspberries have 3 leaflets, but they usually have thorns which eliminates them from being poison ivy. Since Virginia Creeper (Parthenosissus quinqefolia), with 5 leaflets, has some of the same habits, it may be misidentified as poison ivy. The three-lobed Boston ivy (Parthenosissus tricuspidata) often has three leaflets on the plant, which can make it hard to distinguish from poison ivy. Some people confuse the name poison ivy with poison oak (Toxicodendron toxicarium) which is a southern plant that is not known to grow in Nebraska.

Where: Native to the US, poison ivy is found mostly at the forest edge but can be found in the woods. It does well in sandy, gravelly, and loamy soil in disturbed places. In addition, it can be found on lakeshores, and streambanks.

Propagation: Poison ivy reproduces by seed and by roots that can spread several feet from the plant.

Poison Ivy showing some colored foliage in fall.Poisoning: Poison ivy contains an oil call urushiol, which causes dermatitis in most people. Some people do not react, and others become more sensitive each time they come in contact with the plant. Urushiol remains in the plant even when the plant is dead, so take care when removing plants after they have been killed with chemicals. Also, plants should not be burned, as the urushiol will be carried into the air with the smoke and cause an extreme reaction if inhaled. All parts of the plant, including the pollen, are poisonous. Even touching the roots can cause a reaction, as people who have dug in areas with poison ivy can attest to!

The urushiol can be spread by touching things that have come in contact with the plant including tools, animal fur, and clothing, smoke.

Climate Change: Research on climate change by Duke University's Nicholas School of the Environment found that increased levels of carbon dioxide increases photosynthesis, water use efficiency, growth, and biomass of poison ivy. The carbon dioxide growth stimulation exceeds that of most other woody species. Furthermore, plants in higher concentrations of carbon dioxide produce urushiol in concentrations that are 153 times higher. Details can be found online at http://www.nicholas.duke.edu/DEarchives/f06/log-ivy.html

Historical: Poison ivy is native to North America and Asia. It spread to England and Australia because people planted it for its color in the garden.

What: Toxicodendron means poison tree. Cashews have the same urushiol oil in the double shell that surrounds the raw cashew nut. Processing removes the urushiol in the shell. Mangoes are in the same family and very sensitive people have been known to get rashes from the peel of mangoes.

Cons: Dermatitis caused by poison ivy can form blisters within hours, or up to several days after contact.

Pros: Animals seem to be immune to the toxins in poison ivy. Game birds and turkeys eat the fruit and seeds. Deer browse the leaves and twigs. Goats and mice eat the leaves. Caterpillars of a few moths feed on the leaves. Extracts of the leaves have been used to treat herpes, palsy, and rheumatism. Small doses have been used as a sedative. It has also been used to treat paralysis, arthritis, and skin disorders.