Leaves of three, let it be! POISON IVY

By David Sprague

OSU Extension master gardener volunteer

Spending time outside in the warm months is an activity most Ohioans enjoy for the cookouts, the hiking and camping. But nothing can ruin an outdoor activity like coming into contact with poison ivy. For most people, contact with it produces a nasty, itching rash. All it takes is a brushing past the plant. Most never know they touched the plant until the itch starts!

This year has been a great year for the plant. This could be because of the rainy spring and summer of 2015. A wet year frequently leads to more seed production, and thus more seedlings the next spring.

Poison ivy is an American native plant ranging from Canada to South America and is found in all counties of Ohio. It is a perennial, deciduous woody vine, but can also be a shrub. Its distinguishing feature is its leaves always have three leaflets, with the center leaflet usually being the largest. The old saying “leaves of three, let it be” is a reminder to be careful around a vine with three leaflets. While there are always three leaflets, the shape of the leaflets can vary. Poison-ivy leaves are polymorphic, meaning the leaflets can appear in shapes from smooth to serrated to lobed.

Poison ivy is propagated by seed or underground rhizomes and can grow in almost any type of soil, but prefers soil high in calcium. The birds love the seeds, spreading them along fences, under power lines and trees or in your landscaping. Poison ivy is a chameleon; when it grows along the ground it mingles with other vines making it hard to spot. In sunny locations it will grow as an independent, upright shrub. If there are any nearby trees, posts or fences, it races to the sky. When growing in a tree it will vine along the branches, making it look like part of the tree from afar. The vine growing up the tree trunk will put out aerial roots giving it a hairy look.

It produces an oil called urushiol. This oil causes the rash by producing an allergic reaction in your body. All parts of the plant have this irritating oil. The spring and summer are when the plant contains the most urushiol oil, unfortunately matching the time of the year when we are outdoors the most. Anything that comes into contact with poison ivy can pick up the oil: skin, clothing, tools and pets. It only takes 10 minutes of exposure for an eventual rash. Most fact sheets recommend washing with a strong alkali soap, such as yellow laundry or naptha. There are many newer products on the market that remove the oil as well. Rubbing alcohol will dissolve and remove the oil from skin. Although you remove the oil, it may not prevent a rash. Wash affected clothing with normal detergent to remove oil.

The oil is never completely absent from the plant. The plant may look harmless when it’s dormant in the winter, but the oil is still there. Even when it has been dead for many months, the oil is still present and can cause a rash. There are reports of botanists getting a rash after handling poison ivy that had been dead for 100 years.

Mechanical controls (cutting or pulling) or chemical controls are recommended. When using mechanical controls make sure that all skin areas are covered and to launder your work clothes to remove the oil when the job is finished. For chemical control use herbicides that contain glyphosate, triclopyr, or a threeway herbicide that contains 2,4-D amine, dicamba and mecoprop. Remember to read and follow all directions on the package when using herbicides. You may also want to consider calling in a professional to remove it. Poison ivy should not be burned because the smoke, which contains the oil, could cause a serious reaction in the nose, throat or lungs.

Poison ivy may seem to be a useless plant, but in parts of Europe, poison ivy is cultivated for its attractive fall foliage. It is a beautiful red with purple tints in the fall!

For more information on poison ivy see: go.osu.edu/poisonivyphotos

For more information on poisonivy controls see: go.osu.edu/poisonivycontrol