Michigan’s Two Poison Ivy Species

Posted on November 4, 2015 by admin

Eastern Poison Ivy

Western Poison Ivy: left side shows a toothless form. The black dots are dried droplets of urushiol oil. It is milky white when fresh but dries black.

There are two species of Poison Ivy in Michigan. Both species of Poison Ivy have leaves with three leaflets that are notched with large teeth. The lateral leaflets are short stalked and the terminal leaflet has a longer stalk. The teeth are normally found on half of the leaflet, the half closest to the tip. The alternate (singly along the stem) leaves are smooth above, normally shiny and normally they are larger than the leaves of other three leaflet plants. Poison Ivy fruit is a whitish-grayish drupe. (A drupe is a fleshy fruit encasing a seed, for example a cherry or peach). Birds and deer eat the fruit and disperse the seeds.

Eastern Poison Ivy

Western Poison Ivy

Poison Ivy in the winter is recognized by its hairy, grayish, lateral buds with half-rounded or shield shaped leaf scars. There are no stipule scars. The terminal buds end in an abrupt point. Twigs are normally gray but can also have a reddish (or even a greenish) tint. The twigs have many lenticels (dots on twigs) and their pattern is distinct but difficult to describe. If it is Eastern Poison Ivy then it will normally climb and have aerial rootlets without tendrils. The urushiol oil is present in all parts of the plant including the bark and buds so you are not safe from poison ivy in the winter. See blog post for winter twig terminology.

Poison Ivy is in the Anacardiaceae (Cashew or Sumac family). Most of the family’s 800 species are tropical. They include the Cashew, Pistachio, and Mango. Eight species grow wild in Michigan, seven are native.

Although nothing controls common names, the name Poison Oak is best used for species that do not occur in Michigan. Western or Pacific Poison Oak (Toxicodendron diversilobum) occurs along the west coast of the United States. Atlantic poison oak (Toxicodendron pubescens) grows in the southeastern United States.

Eastern Poison Ivy

Eastern Poison Ivy (Toxicodendron radicans), in Michigan, is found mainly south of West Branch. It is a vine that can creep along the ground or climb trees. I have seen branches over three feet (1m) long sticking out from the climbing vine, giving the appearance of a Poison Ivy tree. Sometimes, if it lacks a support, it will form a small shrub. It grows in swamp-forests, floodplains, upland woods, and gardens.

Eastern Poison Ivy, according to William Gillis, “Is distributed from southern Canada to western Guatemala, the eastern third of the United States and throughout Mexico, on Bermuda, and in the western Bahamas, in Japan, western and central China and Taiwan, the Kurile Islands and Sakhalin of the U.S.S.R.” He recognized nine subspecies with the Michigan plants belonging to the subspecies negundo. Negundo refers to Box-elder (Acer negundo) which this plant resembles. (See blog post.)

Eastern Poison Ivy

Eastern Poison Ivy has petioles (leaf stalks) with fine hairs and they are normally shorter than the leafblade is long. Leaflets are flat and narrower than Western Poison Ivy. Normally they are longer than they are wide. Its fruits are smaller than Western Poison Ivy and tend to be grayish-white. Flowering and fruiting clusters hang and normally have 25 or more flowers or fruits in each cluster.

Western Poison Ivy

Western Poison Ivy (Toxicodendron rydbergii) grows north of the Saginaw-Muskegon line but does occur along most of Lake Michigan’s coastline. It is a small woody plant without aerial rootlets so it never climbs. Its petioles (leaf stalks) are glabrous and they are normally longer than Eastern Poison Ivy. Leaflets are cupped and broad, close to as long as they are wide. Its fruits are larger than Eastern Poison Ivy and tend to be whiter. Flowering and fruiting clusters are held upright and seldom droop. They contain few flowers, normally less than 20 in each cluster. It grows in sand dunes, along railroads, on road shoulders, and edges of woods. It is found in sand or gravel. Eastern Poison Ivy is normally in richer soil.

Western Poison Ivy

Hybrids between Eastern and Western Poison Ivy are known and occur along the band where the two species overlap. They are intermediate between the two species.

The two species are normally quite distinct. However, please note the number of times I wrote “normally” when contrasting these two species. Look at a number of characters before deciding which species you are dealing with. I posted this more to illustrate the range of variation in Poison Ivy in Michigan and to explain why it looks different in the northern or southern parts of the state. Caution: These remarks concern Poison Ivy in Michigan, the species vary more outside of the state. Once again, if in doubt, don’t touch it.
Copyright 2015 by Donald Drife

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Poison Ivy Lookalikes

Posted on October 20, 2015 by admin

Eastern Poison Ivy

Recently, I was shown three photos of plants that a person thought were Poison Ivy. Only one was correctly identified. I searched Google Images for Poison Ivy and found several other species that resemble it. The old adage “leaflets three let it be” will keep you away from Poison Ivy and many harmless species.

Western Poison Ivy

There are two species of Poison Ivy in Michigan. Eastern Poison Ivy (Toxicodendron radicans) is found mainly south of the Saginaw-Muskegon line. It is a vine that can creep along the ground or climb trees. It is one of two natives that have aerial rootlets. (The other is Virginia Creeper (Parthenocissus quinquefolia) ). Western Poison Ivy (Toxicodendron rydbergii) grows north of the Saginaw-Muskegon line. It is a small woody plant without aerial rootlets so it never climbs. Both species of Poison Ivy have leaves with three leaflets that are notched with large teeth. The teeth are normally found on half of the leaflet, the half closest to the tip. The alternate (singly along the stem) leaves are smooth above and normally shiny.

Boxelder

Boxelder (Acer negundo) has opposite leaves (leaves in pairs on stem). Its twigs often have a bluish bloom and it is never a vine. Normally its leaves have finer teeth than Poison Ivy. Last weekend, I was at Tawas Point State Park and set up to photograph what I thought was Western Poison Ivy only to discover that it was a Boxelder.

Dewberry and Raspberry (Rubus)

Bramble, Raspberry, and Blackberry (Rubus) often have prickles along the stem. They also might have leaflets with pronounced points. Their leaflet edges are uniformly toothed with fine teeth.

Virginia Creeper

Virginia Creeper (Parthenocissus quinquefolia) has five leaflets not three. It will have aerial rootlets such as Eastern Poison Ivy. If you find it in fruit its berries are purple and not grayish-white like Poison Ivy

Hog Peanut

Hog Peanut (Amphicarpaea bracteata) has three leaflets but they are untoothed. It rarely climbs trees and has a finer stem then Poison Ivy.

Common Strawberry

Common Strawberry (Fragaria virginiana) has blunt leaflets with their teeth uniformly spaced. Their leaf stems are furry and they never creep like Poison Ivy vines do.

Fragrant Sumac

Fragrant Sumac (Rhus aromatica) leaves have numerous blunt teeth and small lobes on their edges. Catkins, or buds of catkins, often appear at the ends of the stems.

The best time to learn the lookalikes is when they are flowering or fruiting. Study their leaves and the leaves of Poison Ivy. If in doubt, don’t touch it.

Thanks to Jason for inspiring this blog.
Copyright 2015 by Donald Drife

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Juneberry: the “Dogwood” of the North

Posted on May 28, 2014 by admin

Juneberries in bloom

I spent last weekend in the area around Grayling, Michigan. Juneberries (Amelanchier sp.) were blooming and the woods sparkled with their soft white flowers. Some of them appeared pink from a distance; however, when seen up close the white flowers had reflected the red of their developing foliage. White flowered Juneberries marked the edges of deciduous woods as their Flowering Dogwood counterparts do in the south.

Juneberry blossoms and new leaves

Six species (or species complexes) are recorded in the Michigan Flora. They are in the Rose Family (Rosaceae) and not closely related to Dogwoods. Their flowering height ranges from one-foot (3dm) to sixty-three feet (19m) in height. They are distinguished by characters of inflorescence shape, leaf venation, leaf toothing, flower shape, petal length, and hairiness of the ovary. Species hybridize and an Ouija board can be as useful as a microscope in determining identification. Ed Voss in the second volume of the Michigan Flora states, “The only virtue Amelanchier has over Crataegus [Hawthorns] and Rubus [Blackberry and Raspberries] is that, by being smaller, it lures us to the hope that it may be more manageable.” If you wish to try identifying Juneberries to species than consult the Michigan Flora website. The “normal” looking plants of each species are distinct but too many plants have not followed the book.

Juneberry blossoms and new leaves

Juneberries are known by a host of common names including, Serviceberry, Shadbush, Shadblow, and Sugarplum. The last name is in reference to the sweet fruit that some species produce. I have eaten fruit off small Juneberry trees in the Upper Peninsula that was as sweet and as juicy as Blueberries.

Look for Juneberries flowering in the north during the next couple of weeks. They are beautiful shrubs in spite of the difficulties in identification.
Copyright 2014 by Donald Drife

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Prickly-ash and the Giant Swallowtail

Posted on September 19, 2013 by admin

For the last forty years (on and off), I have searched for the larva of the Giant Swallowtail (Papilio cresphontes) which feed on Prickly-ash (Zanthoxylum americanum.) Prickly-ash occurs in Tenhave Woods, Oakland County and I have seen adult Giant Swallowtails in the woods for many years. I was helping identify and measure trees in the swamp forest when I found three larvae, the first that I have seen. They resemble bird droppings. A few days later, I found another group of Giant Swallowtail larvae at a highway rest area in Genesee County. This seems to happen to me often, that once I find an insect or plant for the first time I will start finding it at other places.

Giant Swallowtail Larva

Prickly-ash is not an ash but a member of the Rue family (Rutaceae) that includes the citrus. The odor of the flowers and fruit is similar to that of lime and the unripe fruit looks like a tiny lime. The plant is armed with prickles and a stand is painful to walk while doing fieldwork. The twigs and the main leaf stalk have prickles. Prickly-ash grows mainly in the Lower Peninsula but recently a few stations in the Upper Peninsula have been discovered.

Prickly-ash flowers and fruit

The adult Giant Swallowtails have an impressive six-inch (15 cm) wingspan. When it alights on a flower it must continue to flap its wings or the flower stem bends under the butterfly’s weight. This makes the butterfly easy to identify and difficult to photograph. The Giant Swallowtail ranges north to Saginaw. Go out and look for it in southern Michigan.

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Michigan’s Wild-banana

Posted on September 8, 2013 by admin

Pawpaw leaves and fruit

Pawpaw or Wild-banana or American Custard-apple (Asimina triloba) occurs in the southern third of Michigan’s Lower Peninsula. We are at the northern edge of its range. It is Michigan’s only member of the largely tropical Custard-apple Family (Annonaceae).

Pawpaw is a shrub or small tree that can bear fruit on plants as little as a meter (3 feet) tall. In Michigan, they normally grow along rivers in floodplains but also occur in rich deciduous forests and swamps.

Pawpaw flowers

The dark maroon flowers, with three long outer petals and three much shorter inner petals, appear before the leaves expand, and look quite tropical to me. Their foul smell attracts flies that pollinate them.

The leaves are alternate, broadest near the tip and 15 to 30 cm (6 to 12 inches) long.

Pawpaw fruit

Pawpaw has the largest fruit of any native Michigan plant, up to 13 cm (5 inches) long and 2cm (1 inch) thick. It is a large berry containing four to twelve flattened black seeds about the size of a lima bean. The flesh is edible, my favorite wild fruit to eat, although I have friends who hate the taste. The fruiting season is short. Raccoons love them, and have climbed into baskets of Pawpaws as I was carrying them. The picking technique I use is stand to one side of a fruit cluster (so the falling fruit does not hit me), gently shake a small tree and catch the falling fruit. I pick them when they are slightly green but they ripen in a few days.

Pawpaw fruit

The Pawpaw Foundation is developing commercial cultivars. Local farmers’ markets sometimes have them for sale. My preference is to eat them raw or cooked into a custard or Pawpaw bread. See the Foundation’s website for recipes.

Now is the time to pick Pawpaws. Get out and explore a river floodplain and look for Pawpaws with their ripe fruit. Only one of these large berries is needed to provide a sample of their unique taste.
Copyright 2013 by Donald Drife

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Common Buckthorn Invading Michigan

Posted on July 23, 2013 by admin

Common Buckthorn, also called European Buckthorn, (Rhamnus cathartica) was first collected in Michigan in 1914 but reported by Beal in the 1904 Michigan Flora. Billington in his Shrubs of Michigan, published in 1949, still recommends this species as “an excellent hedge plant;” although, he does admit that the “seeds do germinate easily” and they “create a green carpet under the bushes.” This invasive species should never be planted.

An aggressive invader of many habitats in Michigan, this shade tolerant shrub is choking out many native species. While distributed throughout the state, it is common only in southern Michigan, but seems to be spreading in northern Michigan.

It is one of the the first species to leaf out and one of the last to drop its leaves, resulting in a long growing season and giving it an advantage over our native species. The plants are allelopathic, meaning they inhibit the germination of other species. Their fruit is largely responsible for this characteristic so once the species becomes established it aggressively colonizes the habitat. I have seen colonies of Common Buckthorn that have one large “mother-tree” in its center. The seeds are also epigeal, meaning that they germinate on the ground without having to be buried. This allows large numbers of them to germinate.

Common Buckthorn thorns and inner bark

The twigs are tipped with a thorn slightly longer than the buds. The buds, and hence the leaves, are sub-opposite but opposite and alternate nodes occur. The nodes shown in the photo are three successive nodes on the same twig. The thorns occur along the branches and are sharp. These distinguish the plant from Wild Black Cherry, and Choke Cherry.

Common Buckthorn twig

The bark resembles the bark on a Wild Black Cherry but Buckthorn Bark is often redder. Choke Cherry bark is also similar but the lenticels (the large pores) are more prominent in the cherry. If you have doubts, then peel a little of the bark away from a branch and look for the orange inner bark. Most Common Buckthorns have this bark.

Common Buckthorn bark

The leaves are slightly folded, with fine teeth and 3-5 pairs of prominent recessed veins. They are normally a dark green.

The flowers have four yellow-green petals. Male and female flowers occur on different trees and the female trees outnumber the males. A few male trees in a given population can produce enough pollen to pollinate a large colony. I checked 60 shrubs in one colony looking for male flowers to photograph and could not find any. This same colony heavily fruited that year indicating there was no shortage of pollen.

Common Buckthorn flowers, leaves, and fruit

The fruit is a three to four seeded drupe that is eaten by birds. A drupe is a fleshy fruit that surrounds a hard pit or pits. Cherries are an example. Most Common Buckthorns fruit heavily, so once a few plants begin to colonize an area it can rapidly take over. The seeds remain in the seed bank for a relatively short period (three to five years). After we cut a large stand in Royal Oak, Michigan, seedlings continued to appear for the next three years.

Michigan Natural Features Inventory has an excellent site on Common Buckthorn.

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Bladdernut (Staphylea trifolia): the “wind rattler”

Posted on December 9, 2012 by admin

Bladdernut pods

Bladdernut buds

One winter day, when I was about ten-years old, my father took me for a walk in Bloomer State Park. It was a cold, clear day with a slight breeze. We were walking quietly along a trail birding and heard a rattling sound. The sound came from brown, papery pods of a shrub that looked like an escaped ornamental. There were 100s of them hanging on striped branches. The rounded leaf buds were opposite and the twigs had false terminal buds. [Opposite buds are in pairs and false terminal buds can be at the ends of twigs but they have a leaf scar.] After returning home, I looked in The Shrub Identification Book by George Symonds and discovered that they were Bladdernut (Staphylea trifolia) pods.

Bladdernut flowers

The following May we visited the Bladdernut colony again to look for flowers. The flowers are greenish-white bells that hang in panicles. A panicle is a group of flowers on a branched stem. Flowers occur when the leaves begin developing. They are a pretty sight in the springwoods. The opposite leaves have three leaflets and fine teeth.

Staphyleaceae is a small family of approximately 50 species worldwide. Michigan’s only member is the Bladdernut. Its native range in Michigan is south of Bay City. The seedpods are buoyant raising the question of their dispersal via water.

Bladdernut twig

This distinctive plant is great in the garden with its attractive flowers, interesting fruit, and striped twigs. It suckers freely and normally forms a dense clump. It grows in medium shade and does not do well at a dry location. Garwood and Horvitz report that this “is a self-incompatible temperate woodland shrub.” This means two plants are required for heavy seed production. However, they provide data that show some pods form with only a single plant. My single plant produces 10-30 pods a year. Bladdernut is best grown from seeds, but they are double dormant. This means that without treatment the seeds require two freeze cycles before they germinate. Seeds planted in the fall will emerge in the second year.

If you are walking along a river or in a floodplain look (or listen) for this plant. I love to find this plant. Maybe I’ll go to Bloomer Park and see if the colony still exists forty-three years later.

Don Drife

Works Cited

Garwood, Nancy C. and Carol C. Horvitz. Factors Limiting Fruit and Seed Production of a Temperate Shrub, Staphylea trifolia L. (Staphyleaceae). American Journal of Botany, Vol. 72, No. 3 (Mar., 1985), pp. 453-466. Article Stable URL: http://www.jstor.org/stable/2443538.

Symonds, George W. D. The Shrub Identification Book. M. Barrows and Co: New York, 1963. [This useful pictorial guide for identifying shrubs is still in print. The scientific names are a little dated but this is a minor detail.]

Witch-hazel Michigan’s late-bloomer

Posted on October 23, 2012 by admin

Witch-hazel flowers

Witch-hazel (Hamamelis virginiana) is a large shrub or small tree that blooms in the fall in Michigan. It grows in the Lower Peninsula and the western half of the Upper Peninsula. Outside of Michigan, it grows throughout the eastern United States reaching its western limit in Texas and Oklahoma. It is the last of our native woody plants to blossom. The flowers appear in most years after the plant has dropped its leaves. The yellow flowers with their four wiry petals form a pretty sight in the fall woods.

Hamamelis virginiana, Witch-hazel, Michigan

Witch-hazel, Oakland Co., Michigan

Witch-hazel, Tenhave Woods, Oakland Co., Michigan.

The seeds ripen about the same time as the plant flowers. The seedpods shoot the seeds ten to fifteen feet. When I was a boy in Middle School, I had a Witch-Hazel branch with seedpods in my bedroom. (Doesn’t every boy go through this stage?) During the night, I heard a strange “Ping.” The seedpods were drying out and shooting their hard BB-sized seeds against my bedroom mirror.

Spiny Witch-hazel Gall

This plant also produces Spiny Witch-hazel Galls. An aphid crawls into a leaf bud and secretes an enzyme. The irritation causes the plant to produce the gall around the aphid. The aphid reproduces within the gall and the gall provides a food source for the young. The life-cycle is more complex than this involving a secondary plant species host and some broods that are solely females. I cut open a gall from my garden, expecting it to be solid, but instead I discovered it was hollow. Several female aphids (the ones with wings) and at least one male were inside.

I love to see these flowers on their bare branches as I walk though the fall woods. Get out into a rich woods and see if you can find these last flowers of the year.

Spiny Witch-hazel Gall with Aphids

The Michigan Nature Guy’s Blog

To get people looking at, enjoying, and understanding the natural world around them.

Category Archives: Michigan Shrubs

Michigan’s Two Poison Ivy Species

Poison Ivy Lookalikes

Juneberry: the “Dogwood” of the North

Prickly-ash and the Giant Swallowtail

Michigan’s Wild-banana

Common Buckthorn Invading Michigan

Bladdernut (Staphylea trifolia): the “wind rattler”

Witch-hazel Michigan’s late-bloomer