While walking through the woods in northern Michigan, hikers should be aware of several plants that can cause allergic reactions on the skin. The most popular of these plants is poison ivy. This small bush or vine contains an allergin called urushiol oil, which is the cause of the rash that occurs after untreated contact. This oil can be transferred by direct contact, inhalation, or indirect contact, so learning to identify the plant can help woodland enthusiasts from coming in contact with the oil.

Another of these plants is poison oak, which has some similar features of poison ivy, such as the oils they transmit and the location they can be found. These plants can grow anywhere, but prefer growing in areas where there is both direct sunlight and shade, and where the ground has been disturbed.

Poison ivy can be a vine, bush or single plant, and has a tendency to overcome other vegetation. It also can entwine itself around trees and other objects as it grows, creating dense masses of the poisonous plant, according to a bulletin from Michigan State University Extension.

“Poison ivy looks green and yellow in the growing season, and turns a red shade in fall,” Department of Natural Resources forester Chad Fate said. “The leaves can be smooth or slightly serraded on the edges, and the edges can be irregularly shaped.”

The center leaf of the three for both plants almost always has a small stem, and the two side leaves grow directly from the vine. Its leaves are lighter green underneath and fuzzy looking, and in spring, the leaves are bright green. In fall, poison ivy tuns a bright red, and poison oak turns a bright red or orange hue.

Each of the plants can have berries, and they both appear translucent. Poison oak fruit tends to be fuzzy looking, while poison ivy berries are white or cream-colored, and both fruits tend to stay on the plants through the winter and spring.

If contact occurs and the urushoil remains on the skin, a rash will start to occur within two to three days, and will need to be treated, according to Fate. The oil can remain active on clothes, shoes and pets for a long period of time if not washed right away, which could allow continued reinfection and exposure.

“Poison ivy has a tendency to grow along trails and in open areas that have been distrubed,” Fate said. “It shows up in many recreational areas, and usually grows in patches. The plant likes the sun, and usually has a glossy or waxy appearance.”

All parts of poison ivy and oak are poisonous, including its stem, berries and leaves, and can remain poisonous throughout all seasons.

“Poison ivy is a very widespread plant and will grow nearly anywhere in the United States,” Fate said. “Oak, ivy and sumac all have similar toxic oils that require the same types of treatment. As for all plants, if a severe reaction occurs, seek medical attention.”

Other poisonous plants that are lesser known, but just as poisonous or worse:

Poison sumac is typically found in lowland wet areas with a yellowish-white cluster of berries, and is fairly uncommon in Michigan, but has been reported around the area. Poison sumac is often confused with a different breed of sumac that is found on higher dry ground with red berry clusters, but those are not the poisonous plants.

There is an invasive species called Giant Hogweed that has been found in Michigan, and has a tendency to grow in highly disturbed areas. Fate said this plant is toxic and rare, and can grow over 15 feet tall. It can cause severe skin irritation from a clear, watery sap that is exuded from its parts.

Skin contact and sun exposure causes red blotches, painful blisters and later develops into blackened scars. Contact with the sap in the eyes can lead to temporary or permanent blindness. In a Michigan State University Extension bulletin about the plant, it advises people not to touch the plant without proper protection and wash immediately with soap if explosure occurs. For more information on these plants, visit the Michigan Department of Agriculture and Rural Development website at

Nicole Grulke can be reached via email at or by phone at 358-5687. Follow Nicole on Twitter @ng_alpenanews.