Friday, September 19, 2014

The Good, the Bad and the Stinging

by John Windau, Wildlife Communications Specialist, Ohio Division of Wildlife--District Two

“Leaves of three, leave it be” is the old adage used to teach people how to identify and avoid an uncomfortable experience outdoors. However, the axiom is not completely accurate and quite a few plants with three leaves do not need to be avoided, like strawberries and raspberries. Learning to properly identify a few common plants is relatively simple and can help ensure a positive experience, or at least avoid a potentially uncomfortable one when venturing outside.

Poison ivy, poison oak and poison sumac are probably the most famous members of the “plants to avoid” list in North America. The sap of these plants contains the chemical urushiol which can cause an allergic reaction when it contacts the body. The reaction is often an irritating, itching rash that can develop into a more severe reaction in some people. When a plant is injured or damaged, urushiol is released to the plant’s surface. Urushiol is an oil that adheres to anything it comes in contact with including skin, blankets, clothing and pet fur.
Photo from
Usually around 24 hours after contact with the skin, a rash will begin to develop at the point of contact. Rashes usually last for 1 to 2 weeks, but can last up to 5 weeks in some cases. The rash is not contagious, and the fluid from blisters cannot cause the rash to spread. Rashes can only be spread through continued contact with the urushiol oil. Similar to other oils, urushiol does not evaporate and water alone is not very effective at removing the oil. Soaps containing detergents that remove oil are preferred as is plenty of cold water, since hot water opens up skin pores allowing the oil to penetrate. Ordinary laundry detergents can be used to remove urushiol from most clothing and fabrics, except leather and suede.

Poison ivy
The best way to deal with urushiol is to avoid contacting plants that contain it. Of the three aforementioned plants, poison ivy is the most common in Ohio. True to the adage, poison ivy does have three leaflets. The leaflets are oval shaped containing a few narrow teeth along the edges. The center leaflet has a longer stalk than the outside two. Leaflets can vary in color from light green to dark green in the spring and summer, to red, yellow, or orange in the fall. Poison ivy can be a plant, a vine or a shrub, and is thorn less. Poison ivy vines are often “hairy” and the 3 leaflets connect to a stem which connects to the main vine in an alternating pattern.

Poison ivy is sometimes confused with other plants found in Ohio. Virginia creeper is a vine that often grows along tree trunks, similar to poison ivy, but contains 5 leaflets instead of 3 and the vine is “hairless.”

Virginia creeper

Both box elder, a member of the maple family, and fragrant sumac have leaflets similar to poison ivy. The leaflets of box elder saplings attach to the main stem opposite of each other, rather than in an alternating pattern like poison ivy.
Fragrant sumac is a small shrub found in half of Ohio’s counties. The center leaflet of fragrant sumac tapers to the base of the other two leaflets without a long stalk of the poison ivy center leaflet.

Poison sumac is the only other of the infamous three plants that is found in Ohio. It is mostly confined to the northeastern part of the state, and even in that region it is a rare occurrence. Poison sumac is a shrub with leaves containing 7 to 13 oblong leaflets with smooth edges. The stems of the shrub are hairless. It is almost always found in wet locations, like sphagnum bogs, fens and swamps.
Poison sumac
Poison sumac should not be confused with the common staghorn and smooth sumacs which are abundant throughout Ohio.
Staghorn sumac
Common sumac

Stinging nettle
Stinging nettle is another Ohio plant that can quickly turn a hike into an unpleasant situation. Unlike poison ivy and poison oak, stinging nettle does not contain the oil urushiol. Instead, stinging nettle, as the name implies, has very fine stinging hairs on the leaves and stems called trichomes. The trichomes act like tiny needles that inject multiple chemicals into the skin which cause a stinging sensation. Ironically, stinging nettle is edible and may have medicinal uses when handled properly. Stinging nettle grows 2 to 4 feet tall and can be found in fertile soils, often in forest floodplains and along stream banks. The dark green leaves are oval in shape, have a rough paper-like texture and contain very coarse teeth along the edges.

Jewelweed or Touch-Me-Not
Jewelweed is another important plant to know before heading outside, but for a very different reason. Despite one if its common names, touch-me-not, jewelweed is an important medicinal herb and can often relieve the adverse effects of stinging nettle, mosquito bites and bee stings. Some even claim that jewelweed can prevent poison ivy. The waxy leaves of jewelweed are oval in shape, with a few rounded teeth along the leaf edges. The stem is succulent and translucent with a clear liquid inside, which contains the anti-inflammatory ingredients. Interestingly, jewelweed prefers shade and moist soils near running water, which is often where stinging nettle is found.

So whether you are heading into your backyard or hiking deep into the back country, being able to identify a few common plants can have a dramatic difference on the outcome of your trip. If you are interested in learning more about Ohio’s wild plants, there are a variety of excellent field guides available as books or online. Although plant identification may seem overwhelming at first, a good field guide will help point you in the right direction.

Most photos were taken from The Ohio State University Extension or USDA websites.