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Eastern Poison Ivy,
Also known as Central poison ivy or Climbing poison ivy;
Toxicodendron Radicans

Often called only Poison ivy, its botanical name is Toxicodendron radicans. Six subspecies of the T. radicans exist (divaricatum, eximium, negundo, pubens, radicans, verrucosum) but I will not dwell on these subjects. Discovered by the first settlers, Eastern poison ivy is present in the eastern United States. This species of toxicodendron generates fine aerial roots that allow the plant to cling to the bark of trees and rise up to the top of them. That’s the major difference between Eastern and Western poison ivy. Also, “radicans” means “having rooting stems.” The Eastern poison ivy can be a climbing or crawling vine or be a shrub. The Western poison ivy (Rydberg) only crawls. Some still consider the Western poison ivy  as a subspecies of the Eastern poison ivy.

Eastern Poison Ivy (Toxicodendron radicans) climbing on a tree. Copyright http://weedscanada.ca/cashew.html
Eastern Poison Ivy (Toxicodendron radicans) climbing on a tree. Copyright http://weedscanada.ca/cashew.html

Leaves

The saying “Leaves of three, let it be. Leaves of five let it thrive.” teaches us to beware of a plant that has three leaves. That is the case with the two poison ivies, and the two poison oaks. The leaf is a group of three leaflets at the end of a stem (petiole), which links the trunk. The central leaflet, pointing outward, has a longer stalk than the two others. The leaflets are egg-shaped ending in a point. The edges can be smooth, toothed or wavy. The leaves length can also vary greatly depending on the maturity of the plant, the soil type and the region. The leaves have a glossy (polished appearance) reddish in spring, green in summer and take different shades of yellow, orange, red or bronze in the fall.

Smooth poison ivy leaves

Nonclimbing and climbing Eastern poison ivy: 3 leaves with smooth edges.
Nonclimbing and climbing Eastern poison ivy: 3 leaves with smooth edges.

Toothed poison ivy leaves

Eastern climbing poison ivy (T. radicans) can have toothed leaves.
Eastern climbing poison ivy (T. radicans) can have toothed leaves.

Smooth poison ivy leaves in autumn

Climbing Eastern poison ivy (T. radicans) at fall with red leaves. Copyright http://weedscanada.ca/cashew.html
Climbing Eastern poison ivy (T. radicans) at fall with red leaves. Copyright http://weedscanada.ca/cashew.html

Trunk and stems

Climbing poison ivy (T. radicans) with earial rootlets on a tree. Closely.
Climbing poison ivy (T. radicans) with earial rootlets on a tree. Closely.

Eastern poison ivy is a woody plant that climbs on trees, posts and anything vertical. Eastern poison ivy is a vine that goes up and, sometimes, a shrub. We can easily recognize the climbing Eastern poison ivy by the fine aerial roots that allow the plant to cling to the bark of trees. With all these fine roots, the trunk can sometimes look like a tousled old rope. The texture of the trunk is always slick with a grey-brown color. As the plant become stronger and the trunk wider, the plant can spread laterally to 8 feet or more from the trunk to reach sunlight. The trunk and stem, like all parts of this plant may cause skin irritation if broken and if the urushiol break out.

Climbing poison ivy (T. radicans) with aerial rootlets. 
Copyright http://weedscanada.ca/cashew.html
Climbing poison ivy (T. radicans) with aerial rootlets.
Copyright http://weedscanada.ca/cashew.html

The poison ivy shrub, a variant

The Toxicodendron radicans subsp. negundo also named Toxicodendron negundo is the shrub variant of the Eastern poison ivy. It doesn’t climb on the trees but grows as a small tree. It is also possible to see the little aerial rootlest on the branches.

Flowers and fruits

In June and July, some plants produce beige to yellow-green discrete flowers. These flowers are sometimes hidden by the leaves and hard to see. In late spring, beige round fruits with 1/8 to 1/4 in (3-7 mm) diameter, appear in clusters.

Eastern poison ivy (T. radicans) as a shrub with flowers and fruits.
Eastern poison ivy (T. radicans) as a shrub with flowers and fruits.

Propagation

This vigorous plant is propagated by its seeds, located within fruit. The fruit can drop near the plant or birds can eat the fruit and expel the seeds later in their droppings. Another plant can then push in this place, if the germination is done correctly. The poison ivy also spreads by suckering from its long root system located at the surface or just below the ground.

Poison ivy (Toxicodendron radicans) drawing.
Poison ivy (Toxicodendron radicans) drawing.

Habitat and distribution

Eastern poison ivy is present in the eastern half of United States, up to the southern Ontario, Canada. If this variety of poison ivy is absent north of these regions is because its long aerial stems cannot withstand harsh winters.

You can find eastern poison ivy in various types of soils, in sunny or partial shade, wetlands, dry, sandy or rocky, on the edge of fields, roads, railways, rivers. The place where the plant is established is often densely settled and is spreading rapidly in deforested and disturbed lands. This plant can grow well where many other plants can not, such as dry, rocky and acid soils. Always keep your eyes open.

Climbing poison ivy habitat area (toxicodendron radicans).
Climbing poison ivy habitat area (toxicodendron radicans).

Videos about Eastern poison ivy

How to identify poison ivy and stay away!
Poison Ivy and Poison Vine/Oak Identification
Facts about poison ivy and how to correctly identify poison ivy, poison oak and poison sumac.
Best Poison Ivy Video Identification Guide

Resources about Eastern poison ivy

Western poison ivy:
Also known as Rydberg’s poison ivy, Canadian poison ivy, Northern poison ivy, Nonclimbing poison ivy;
Toxicodendron Rydbergii

The botanical name of western poison ivy is Toxicodendron Rydbergii, but let’s shed a little light on their names. Western poison ivy and Eastern poison ivy have long been known and named as rhus radicans, then toxicodendron radicans, considering that it was one plant with two behaviors. Later, botany decided to separate the two variants: toxicodendron rydbergii for the creeping variety (on the ground) that sometimes appears as a shrub; toxicodendron radicans for climbing variety (in height). However, some botanists still disagree with this division. Often, the printing and web literature on the subject still brings together both types of poison ivy under the same term toxicodendron radicans and the mistake recurs over the years. Even Wikipedia and some documents from departments continue in this same old habit. In addition, in regions where both plants are present, hybridization between them can make it difficult to identify the plant.

Nonclimbing poison ivy (T. rydbergii) on a rocky area. Copyright http://weedscanada.ca/cashew.html
Nonclimbing poison ivy (T. rydbergii) on a rocky area. Copyright http://weedscanada.ca/cashew.html

Leaf

The saying “Leaves of three, let it be. Leaves of five let it thrive.” teaches us to beware of a plant that has three leaves. That is the case with the two poison ivies, and the two poison oaks. The leaf is a group of three leaflets at the end of a stem (petiole), which links the trunk. The central leaflet, pointing outward, has a longer stalk than the two others. The leaflets are egg-shaped ending in a point. The edges can be smooth, toothed or wavy. The leaves length can also vary greatly depending on the maturity of the plant, the soil type and the region. The leaves have a glossy (polished appearance) reddish in spring, green in summer and take different shades of yellow, orange, red or bronze in the fall. The leaves are the highest part of the plant and can rise up to 20 in (50 cm) from the ground in sunny and suitable locations. In warmer regions, such as the eastern United States, western poison ivy can be a small shrub that can reach 3 feet (1 meter).

Western poison ivy (T. Rydbergii) can hav toothed leaves.
Western poison ivy (T. Rydbergii) can hav toothed leaves.
Nonclimbing and climbing Eastern poison ivy: 3 leaves with smooth edges.
Nonclimbing and climbing Eastern poison ivy: 3 leaves with smooth edges.
Nonclimbing poison ivy (T. rydbergii) between a forest and a field.
Nonclimbing poison ivy (T. rydbergii) between a forest and a field.

Trunk and stems

 Stem of the nonclimbing poison ivy (T. rydbergii) at spring. Copyright http://weedscanada.ca/cashew.html
Stem of the nonclimbing poison ivy (T. rydbergii) at spring.
Copyright http://weedscanada.ca/cashew.html

Poison ivy is a woody plant, not herbaceous. Thus, when the three leaves are fallen, the trunk is like a twig persistent in autumn and winter, which can go up to 20 cm (8 in) from the ground in Northern US and Southern Canada. In regions with milder winters, the plant can become a small shrub that can reach three feet. The trunk and stem, like all parts of this plant, may cause skin irritation if broken and if the urushiol break out.

Typical stem-leaves-fruits of the nonclimbing poison ivy (T. rydbergii) in summer.
Typical stem-leaves-fruits of the nonclimbing poison ivy (T. rydbergii) in summer.

Flowers and fruits

In June and July, some plants produce beige to yellow-green discrete flowers. These flowers are sometimes hidden by the leaves and hard to see. In late spring, beige round fruits with 1/8 to 1/4 in (3-7 mm) diameter, appear in clusters. Often they remain throughout fall and winter on the main stem.

Fruits of the nonclimbing poison ivy (T. rydbergii) in autumn. Notice the red leaves. Copyright http://weedscanada.ca/cashew.html Fruits of the nonclimbing poison ivy (T. rydbergii) in autumn. Notice the red leaves. Copyright http://weedscanada.ca/cashew.html
Fruits of the nonclimbing poison ivy (T. rydbergii) in autumn. Notice the red leaves. Copyright http://weedscanada.ca/cashew.html Fruits of the nonclimbing poison ivy (T. rydbergii) in autumn. Notice the red leaves.
Copyright http://weedscanada.ca/cashew.html
Fruits of the nonclimbing poison ivy (T. rydbergii) in autumn. Notice the red leaves. Copyright http://weedscanada.ca/cashew.html Fruits of the nonclimbing poison ivy (T. rydbergii) in autumn. Notice the red leaves. Copyright http://weedscanada.ca/cashew.html
Fruits of the nonclimbing poison ivy (T. rydbergii) in autumn. Notice the red leaves. Copyright http://weedscanada.ca/cashew.html Fruits of the nonclimbing poison ivy (T. rydbergii) in autumn. Notice the red leaves.
Copyright http://weedscanada.ca/cashew.html

Propagation

This vigorous plant is propagated by its seeds, located within fruit. The fruit can drop near the plant or birds can eat the fruit and expel the seeds later in their droppings. Another plant can then push in this place, if the germination is done correctly. The poison ivy also spreads by suckering from its long root system located at the surface or just below the ground. In southern regions, aerial stems can stand milder winters and plant growth can continue in height. So suckering propagation becomes less important.

 Nonclimbing Poison Ivy (Toxicodendron rydbergii) drawing.
 Nonclimbing Poison Ivy (Toxicodendron rydbergii) drawing.

Habitat and distribution

Let’s start in the north. Western poison ivy is found in southern Canada, from the Fraser valley in B.C. to the Maritimes, with the exception of Newfoundland. As you move northward, the less you will have the opportunity to meet the plant. It seems that the western poison ivy can not stand harsh winter cold. By the way, no other toxicodendron can live in these regions. We now know where to take our next vacation.
In United-States, this plant is also widely present in the Rockies, from north to south, and up to the north-eastern states. The south-eastern states and the west coast are free of western poison ivy.
You can find western poison ivy in various types of soils, in sunny or partial shade, wetlands, dry, sandy or rocky, on the edge of fields, roads, railways, rivers. The place where the plant is established is often densely settled and is spreading rapidly in deforested and disturbed lands. This plant can grow well where many other plants can not, such as dry, rocky and acid soils. Always keep your eyes open. Usually, very shady places, such as maple and dense forests, are less suitable for propagation.

 Nonclimbing Poison Ivy (Toxicodendron rydbergii) drawing.
 Nonclimbing Poison Ivy (Toxicodendron rydbergii) drawing.

Videos about Western poison ivy

Facts about poison ivy and how to correctly identify poison ivy, poison oak and poison sumac.
Survival Skills 101: How to Identify Poison Ivy, Poison Oak & Poison Sumac

Resources about Western poison ivy

Similar plants looking like poison ivy

Virginia creeper

Botanical name: Parthenocissus quinquefolia.
It is a completely harmless woody climbing plant widespread in the same areas as poison ivy. However, it has five leaves with a crumpled texture and toothed edges. Unlike eastern poison ivy, the texture of its trunk is rough with a brown color. I have long believed, wrongly, that it was poison ivy.

Virginia creeper: recognizable with its 5 leaves.
Virginia creeper: recognizable with its 5 leaves.

More about Virginia Creeper:

Poison Ivy and Virginia Creeper Vines

Western blue virginsbower

Botanical name: Clematis occidentalis.
It is also a creeping or climbing vine. Its leaves are on opposing sides of the stem: 2 leaves out of each node along the main stem. The leaves are tipped and toothed. Its flowers, larger than those of poison ivy, are white or blue.

Western Clematis can climb everywhere in an undergrowth. Copyright: Walter Siegmund.
Western Clematis can climb everywhere in an undergrowth. Copyright: Walter Siegmund.

More about Western blue virginsbower:

Hog-peanut

Botanical name: Amphicarpaea bracteata.
A vine with three alternate leaves like poison ivy. However, the leaves are drop shaped and have smooth contour. The plant bears clusters of small white purplish flowers. The main stem is fine and thin.

 Hog-Peanut, with flowers, rolling up along an other plant.
 Hog-Peanut, with flowers, rolling up along an other plant.

More about hog-peanut:

River Bank Grape

Also known as:  Frost Grape.
Botanical name: Vitis riparia.
This vine is common in the United States and southern Canada. It likes the same areas as poison ivy but its leaves quickly reassure us about its identity. The leaves, totally different from poison ivy, are typical of grapes vine: big and toothed.

River Bank Grape or Frost Grape with large jagged leaves. We can see a poison ivy plant right in the middle.
River Bank Grape or Frost Grape with large jagged leaves.
We can see a poison ivy plant right in the middle.

More about Western River bank grape:

Riverbank Grape

Box elder

Also known as: boxelder maple, ash-leaved maple and maple ash
Botanical name: Acer negundo with 3 subspecies (subsp. negundo, subsp. interius, subsp. californicum).
It is a fast-growing and short-lived tree that grows up to 33 to 82 feet (10 to 25 metres) tall. The shoots have a light green color with a whitish to pink or violet waxy coating. The 3 leaflets are about 2 to 4 inches (5 to 10 centimetres) long with slightly serrated margins. Leaves have a translucent light green colour and turn yellow in the fall. The shape of the leaflets resembles poison ivy but are are thinner. The well-known “flying” fruits of the box elder are absolutely different from poison ivy.

Box Elder, leaves and fruits (Acer negundo) by Agnieszka Kwiecien
Box Elder, leaves and fruits (Acer negundo) by Agnieszka Kwiecien

More about Box elder:

Box Elder (Acer Negundo) identification video

Kudzu

Also known as: Japanese arrowroot
Botanical name: Pueraria montana.
Kudzu was introduced from Japan to the USA at the Japanese pavilion in the 1876 Centennial Exposition in Philadelphia. It is now common throughout most of the southeastern United States and it is spreading year after year. Kudzu has been  present in southern Ontario, Canada, since 2009. This plant is an invasive climbing vine with 3 leaflets, like various poison ivies. Its leaflet has a more round shape and is more translucent than poison ivy.

Kudzu: an invasive vine
Kudzu: an invasive vine
kudzu: leaf with 3 leaflets
kudzu: leaf with 3 leaflets

More about Kudzu: