Poison ivy, the notorious cause of itchy, blistery rashes, grows throughout the continental United States and much of Canada. (1)
The plant can be found in forests and wetlands, on beaches, and along streams, as well as in urban settings such as parks, yards, and along roads. Poison ivy prefers partial sunlight, so it often grows where the land has been disturbed, such as along the edges of trails, fields, or landscaping.
There are two types of poison ivy — eastern and western — which have somewhat different geographic ranges but which look very similar and sometimes interbreed where their ranges overlap. (2)
Both types of poison ivy spread along the ground, and eastern poison ivy also climbs trees, shrubs, walls, fences, and other structures, clinging to its host with hairy rootlets and sometimes sending out horizontal branches.
Leaves of Three …
Most people know the phrase “Leaves of three, let it be,” but many plants have leaves that grow in clusters of three, so it helps to know a bit more about the physical appearance of poison ivy.
Each poison ivy leaf (or, more accurately, leaflet) has a small leaf stem at its base, attaching it to a stalk or small branch that connects to the main poison ivy vine. The leaflet in the middle of the threesome usually has a longer leaf stem than the two side leaflets.
Poison ivy leaflets are about twice as long as they are wide. They are typically two to five inches long but may reach six or more inches if conditions are right.
Poison ivy leaves may be smooth-edged or may have lobes or teeth. The two sides of the leaf may or may not be symmetrical.
Leaves may be red or green, shiny or dull. The plants may have flower buds, flowers, or berries in dense clusters close to the vine.
... Let It Be
According to the American Skin Association, as many as 50 million Americans have a poison ivy reaction each year. (3)
The cause of poison ivy reactions is urushiol, an oily resin that’s found in the leaves, stems, and roots of the poison ivy plant; most people are allergic to it.
Urushiol sticks to skin, clothing, fur, gardening tools, and other surfaces when it comes into contact with them.
Washing the oil off your skin immediately after contact may prevent a rash from developing. Soap and water is effective, as are commercial poison ivy washes, but the key in either case is to wash the oil off quickly, before the allergic reaction begins.
Following contact — or even potential contact — with poison ivy, you should also wash your clothing and footwear and any gear or equipment that could have touched the poison ivy plant. It’s also important to wash pets who may have gotten urushiol on their fur so they don’t pass it on to you.
How Poison Ivy Looks in Springtime
Poison ivy loses its leaves in the winter and grows new ones in the spring. Young poison ivy leaves often start out dark red and shiny, then gradually turn green and less shiny over time.
Mature leaves generally have a pointed tip, but new leaves may be rounded at the tip initially.
In addition to leaves, the poison ivy plant may grow clusters of small, green of flower buds in spring.
Poison Ivy in Summer
In summer most poison ivy leaves are green, although new leaves may still appear reddish at first, and the leaf edges and stems of the plant sometimes stay red.
Poison ivy vines often take over an area, crowding out other plants and creating a carpet of poison ivy. It can also weave itself in among other plants, sometimes covering an entire field of grasses or other low plants. And it can create a wall of foliage on fences, abandoned buildings, or sunny rock outcroppings.
Individuals who choose to wear shorts, short sleeves, or sandals outdoors in hot weather should look carefully before touching or walking through any greenery. Similarly, hikers and other outdoorspeople should stay on trails and be extra careful when stepping off the trail to heed the call of nature.
Poison Ivy in Fall: Beautiful but Treacherous
Poison ivy is one of the first plants to change color in the fall, and its leaves can turn a brilliant red, yellow, or orange. They may be tempting for leaf collectors, but don’t touch! They can still give you a rash, just like green poison ivy leaves.
A camera is the best way to capture the seasonal beauty of poison ivy.
Poison Ivy in Winter: Hairy Vines on Tree Trunks
In winter, poison ivy loses its leaves, but it can still cause a rash if you touch the hairy vines that remain. The hairs are actually rootlets that attach the vine to the surface it’s climbing.
In the eastern United States, you’ll often see the vines clinging to the trunks of trees, but they may also be found on shrubs, buildings, stone walls, fences, utility poles, and other structures.
Poison ivy vines can be as much as six inches thick, and they may have thinner branches sticking out horizontally.
Poison Ivy Flower Buds
Poison ivy flower buds are small and green or greenish-yellow and form in clusters, close to the vine. They emerge in the spring, soon after the first leaves come out.
Poison Ivy Flowers
The flowers of poison ivy are small and off-white, with orangeish centers. The flowers grow in clusters, just like the buds, and bloom in the spring.
Poison Ivy Berries: Strictly for the Birds
Poison ivy flowers develop into berries in the late summer. They are initially green, then ripen to a whitish color in early fall. They are edible for birds but not for humans.
Poison ivy berries are easier to see in winter, because they are not hidden by leaves. However, because of the absence of leaves, it may be harder to identify them as poison ivy.
In general, touching or eating any berry you don’t recognize is not recommended.
Be Careful What You Touch or Burn
Before you hug a tree or even lean against one, make sure there are no poison ivy vines growing up it. In the spring, summer, and fall, the vine will likely have leaves attached to it, but in the winter, it won’t. One giveaway that a vine might be poison ivy is the hairy rootlets attaching the vine to the tree.
People collecting firewood should similarly be careful to avoid tree trunks with poison ivy vines attached. The vines themselves still contain urushiol, and cutting them will expose you and your tools to it. Even if you avoid getting poison ivy when cutting the firewood, you can release dangerous amounts of urushiol by burning it.
Burning poison ivy can cause a very serious allergic reaction in anyone who comes in contact with or inhales the resulting smoke.
The safest way to dispose of poison ivy is to bury it or to stack it in a place where no one will come in contact with it for at least a year.
Watch Where You Step!
Small poison ivy plants growing along the ground may be easy to overlook, but brushing against them can still result in the characteristic poison ivy rash.
If you know you’ll be in a location where poison ivy is possible, such as a forest, wetland, field, orchard, or public park, consider wearing closed shoes and long pants to protect your legs and feet. Wash your clothes and shoes promptly when returning home.
If you have to work around poison ivy, you may want to try using a barrier cream (available at pharmacies) on your hands and any exposed skin for added protection.