Which trees keep their dried leaves throughout the winter?

Fagus grandifolia

American Beech in winter

A winter walk through a woods in Michigan will reveal deciduous trees holding their dried leaves from last fall. Marcescence is the technical term for plant parts that wither but do not fall off. It can refer to leaves, flowers, or fruit. In deciduous leaves an abscission layer forms at the base of the petiole (leaf stem). In most deciduous leaves the abscission layer hardens on the twig side in the fall, the leaves drop-off, and this layer protects the bud-scar on the twig. In marcescent leaves, the abscission layer does not function until buds break in the spring. Andrew Hipp at The Morton Arboretum explains this in greater detail.

Some species are more marcescent than others. Oaks, Beeches, Hornbeams, and Hop-hornbeams commonly hold their leaves. Younger trees exhibit marcesence more often than mature trees. Stress from drought or disease can cause marcescence in any deciduous species .

The color of the winter leaves is normally distinctive but hard to describe. With a little practice you can learn to identify these trees at a distance. Of course, looking at the shape of the leaf, winter bud, or the bark can confirm your identification.

Fagus grandifolia

American Beech leaves in winter

Marcescent leaves on American Beech (Fagus grandifolia) bleach from tan to a ghostly cream-color during the winter. Looking closely at a twig you will see long buds that confirm the identification.

Ostrya virginiana

Hop-Hornbeam leaves and winter bud

Hop-hornbeam (Ostrya virginiana)  has winter leaves that tend to curl. Once again, with practice the color is distinctive. Blue-beech or Hornbeam (Carpinus caroliniana) is similar to Hop-hornbeam but with lighter brown leaves.

Carpinus caroliniana

Blue-beech winter leaves

Oaks (Quercus spp.), especially the Black Oak group (subg. Erythrobalanus), tend to hold their leaves. Some years ago, when Dr. Warren Wagner was studying Shingle Oak (Quercus imbricaria) we learned to identify the species when we drove by. Shingle Oak leaves are tan or “potato-brown color.” Other oak species have a darker, reddish-brown color. Shingle Oak is Michigan’s only simple-leaved oak. Its leaves look more like bay leaves than what we in the north think a “typical” oak leaf should resemble.

Shingle Oak – L                                                                     Pin Oak – R

It is fun to walk through a winter woodlot and identify the leaf-holding species. In Tenhave Woods, in Royal Oak, you can see where the ridges run through the woods by looking at the location of the Beech trees. Hornbeams ring the low swamp forest. Winter often is the best time to get an overview of an area when you can see farther and having the ability to identify some species from a distance is helpful.

Copyright 2017 by Donald Drife

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What is Killing the Jack Pine?

Sphaeropsis shoot blight

Sphaeropsis shoot blight

Last Fall, my friend Trapper Dave contacted me and asked what was killing the Jack Pine (Pinus banksiana) in a Kirtland’s Warbler planting near his cabin in Oscoda County. This planting was the subject of an earlier blog post. Needles on branches and entire trees suddenly turned brown. We checked other plantings and found dead trees several other places in Oscoda, Crawford, and Montmorency counties. Several of these stands were two year old Kirtland’s Warbler plantings and we became concerned about the impact this die-off might have on this endangered bird.

Trapper Dave contacted the DNR and a helpful Forest Health Technician replied that, “We have had several reports from roughly a four county area of this type of mortality. The pictures you sent are consistent with other pictures we have received from this area… I’ll be sure to send you a some more information once we are able to make a diagnosis.”

Later we received a report from the Diagnostic Services at Michigan State University. They identified Sphaeropsis canker (Sphaeropsis sp. or spp) as the cause of the die-off. From the limited sample, submitted by the Forest Technician, they could not identify which species it was or even if more than one species is involved. The genus is poorly understood and probably has many undescribed species.

Sphaeropsis shoot blight

Jack Pine needles showing Sphaeropsis shoot blight

I looked up the fungus in Tree Maintenance (6th edition) by Pirone, Hartman, Sall, and Pirone. They list another newer generic name, Diplodia but use Sphaeropsis. They write that the fungus “overwinters in infected needles, twigs, and cones. In spring, the small fruiting bodies release egg-shaped, light brown spores… The fungus grows down through the needles and into the twigs, where it destroys tissues as far back as the first node.” (page 425).

Sphaeropsis shoot blight

Close-up of needle showing Sphaeropsis shoot blight spores

Several sources state that the spores overwinter in the cones but I could not find spores in the half-dozen cones I checked. The fungus kills the branches quickly. Die-off appeared over a two-week period but the trees must have been infected for most of the summer.

A USDA Northeastern Area Fact Sheet states, “Sphaeropsis shoot blight, formerly called Diplodia shoot blight, is worldwide in distribution and can infect many conifer hosts. Although many pine species are reported hosts, this disease causes severe damage only to trees that are predisposed by unfavorable environmental conditions. …Other predisposing environmental factors include poor site, drought, hail or snow damage, compacted soils, excessive shading, insect activity or other mechanical wounding. In the north-central United States, the most common hosts are Austrian, Scotch, mugo, red and jack pines grown in ornamental and windbreak plantings.”

We need to monitor the extent of the shoot blight damage in the Grayling area. It is a native fungus attacking a native tree that should have defense mechanisms. It was a dry year in the Grayling area so this may have made the trees more susceptible to infection. I am concerned that the USDA lists Jack Pine plantings, which of course is what we do for Kirtland’s Warbler, as being more susceptible to the infection. I did not find the fungus in the half dozen naturally occurring Jack Pine stands that I checked. If you find this fungus please report the location in the comments section of this blog post.
Copyright 2016 by Donald Drife

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I Listen to the Trees

Populus tremuloides

The author and his niece listening to an Aspen

The January-June, 2015 issue of The Michigan Botanist is a tribute to Burt Barnes who died in 2014. Dr. Barnes co-authored Michigan Trees with the late Herb Wagner. This is my go to book for information on Michigan trees. Dr. Barnes was a forest ecologist and an expert on Aspens and Birches. One photograph caught my eye. It shows Dr. Barnes with his ear pressed against a small Aspen. Its caption reads, “Burt Barnes listens for ‘the sound of bells’ along the trunk of a young aspen tree as the wind blows its leaves” (page 77). The article does not state if they heard anything. It even says, “someone had jokingly told him” this. I needed to find out what they heard.

A few days later, my niece and I spent an evening listening to tree trunks. Pressing one ear against a Quaking Aspen (Populus tremuloides) trunk and blocking the other ear so I would not hear the wind through the leaves I listened. Whenever the wind rustled the leaves, the trunk sounded similar to a light gentle rain. We listened to Quaking Aspens of different sizes from 2 inches [5cm] to 18 inches [45cm] hearing the sound from every tree. We heard the same sound from Bigtooth Aspen (Populus grandidentata) and their hybrid (Populus xsmithii).

Populus grandidentataPopulus tremuloides

Bigtooth Aspen leaves (L) and Quaking Aspen leaves (R)

We then wondered what sounds other trees made. We listened to Black Cherry (Prunus serotina), Red Oak (Quercus rubra), and Red Maple (Acer rubrum) and heard no sounds. We visited a stand of Balsam Poplar (Populus balsamifera) and heard no sounds from the trunk of this Aspen relative.

Why is the rain sound heard only in Aspens? Does the density and structure of the wood transmit sound better? Do Aspen leaves vibrate at a unique frequency? The sound was produced regardless of the wind speed so perhaps frequency is irrelevant. Or perhaps, as my mentor tells me, this is one of those things we do not understand and we need to embrace the mystery.

Get out and listen to the trees. Enjoy the mystery. And you will probably find something else fascinating in Nature.
Copyright 2016 by Donald Drife

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Soft Maple Flowers

Acer rubrum flowers

Red Maple male flowers

Many people are surprised to learn that trees have flowers. They apparently have not thought through how seeds can develop if there are no flowers. I have been interested in tree flowers since I was given a copy of Norman Fassett’s Spring Flora of Wisconsin when I was a boy. It is a handy little guide to plants that flower in Wisconsin before June 15th and useful throughout Michigan. From it I learned that Red Maple (Acer rubrum) flowers have petals and Silver Maple (A. saccharinum) flowers do not. I began to look for tree flowers.

Acer rubrum perfect flowers

Red Maple perfect flowers

There are additional characters used to distinguish flowers of the two species. Red Maples have separate  sepals and on Silver Maples they are connected. The ovary on Red Maples is hairless and on Silver Maples it is hairy. The soft maples flower before their leaves develop and often I find flowers on the forest floor so it is nice to be able to identify the trees from only their blossoms.

Acer saccharinum flowers

Silver Maple L – male flowers R – perfect flowers

Soft Maples normally have separate male and female flowers. They can be on the same tree. Perfect flowers are known but are rare.

Get out and look at the maples while they are flowering. Watch what is pollinating them. Enjoy one of the first flowers of the year.

Copyright 2016 by Donald Drife

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Spots on Maple Leaves

Rhytisma acerinum

Silver Maple leaves with Tar Spot

Several people have shown me maple leaves with quarter to three-quarter inch (5 to 20mm) diameter black spots. They are caused by a fungus Rhytisma acerinum aptly named Maple Tar Spot. They occur commonly on Silver Maple (Acer saccharinum) and Norway Maple (Acer platanoides). However, they can infect all of our native and introduced maple species.

Rhytisma acerinum

Silver Maple – L                 Norway Maple – R         Leaves showing Tar Spot

Maple Tar Spot is becoming common in southeastern Michigan. A Michigan State University Diagnostic Facts publication from 2011 states, “Historically, significant outbreaks of tar spot occur infrequently. In Michigan, however, we have seen severely infected trees for the last three years.” This trend is continuing. Individual trees are sometimes infected for a single year.

Stomata are produced on the surface of the spots and release spores into the air. Maple Tar Spot does no real harm to the tree. It overwinters on fallen leaves so raking and removing these leaves will help to control the infection.
Copyright 2015 by Donald Drife

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Maple Spinners

Maple Seeds

Maple Seeds Photo by Robert Muller

Recently a friend remarked, “There are not many spinners this year.” I was puzzled until I realized my friend was talking about maple seeds. When I was a kid we called them propellers or helicopters. I took an informal Facebook poll asking what people called them and they added “Whirligigs” or “Whirligiggers” and appropriately “pain in the butt”.  Technically, it is a samara that is defined as “a winged fruit that does not split open.” Elms, Maples, and Ashes have samaras.

Michigan has six native species of Maples (seven if you recognize Black Maple as distinct from Sugar Maple). The non-native Norway Maple (Acer platanoides) is a too common escaped species.

Silver Maple

Silver Maple

Silver Maples (A.sarrharinum) and Red Maples (A. rubrum) have the best spinners. Silver Maple samaras are 3-6cm (1 ¼ to 2 ½ inch) long and the pair forms a widely diverging angle although often only one seed fully develops.

Red Maple

Red Maple

Red Maple samaras are smaller 1-2.5cm (1/2 to 1 inch) long and the pair is more V-shaped. Often they are reddish. Sugar Maple (A. saccharum) pairs are U-shaped with the samara almost parallel to each other.


Boxelder L- dried seeds in winter R-fresh seeds

Boxelder (A. negundo) has V-shaped pairs and will sometimes hang on the tree all winter. Norway Maples have samara pairs widely spaced so the pairs are almost straight across.

Striped Maple

Striped Maple or Moosewood

Mountain Maple (A. spicatum) and Striped Maple also called Moosewood (A. pensylvanicum) have seeds in branched clusters called racemes. Mountain Maple has seeds approximately 1cm (3/8 inch) long. In Striped Maple the seeds are 2cm (3/4 inch) long. I seldom need to identify maples solely from their seeds. All of these species have other useful characteristics to help determine their identity.

Thanks to Robert Muller for the use of his photo showing the seed of the four species.
Copyright 2015 by Donald Drife

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Looking for a champion White-cedar

Dave, Don, and Bill at the tree

Dave, Don, and Bill at the tree

Last year I heard reports of a large White-cedar (Thuja occidentalis) discovered along the mainstream of the Au Sable River. The exact location was carefully guarded to protect the tree from vandalism. Therefore, I was shocked to see an article about this tree in the Oscoda County 2014 Visitors Guide including a cryptic location. Directions were provided to a small parking lot but no information regarding how to get to the tree except that it grows on a “semi-island.” I do not require much of an excuse to convince me to spend a morning walking through the mainstream’s river valley. A couple of friends and I found the tree after searching along the river. Actually, they found it. I was lagging behind, as I usually do, taking photos.

This is a magnificent specimen measuring  1.2m [48 inches] in diameter. The Visitors Guide stated that its age “exceeds 350 years” and a U. S. Forest Service Ranger estimated that it was 500-700 years old. Another common name for this tree is Arbor-vitae which means “tree of life.” An apt name for a long lived tree.

White-cedar’s bark is tough and resists fire. This particular specimen grows in an area that is perpetually damp, which further protects it from fire. Having brittle wood, White-cedar branches often break; indeed, the crown of our champion is broken about 9m [30 feet] above the ground.

Canopy of large Thuja occidentalis

Canopy of large White-cedar

I have seen larger trees many times; even larger White-cedars in the Valley of the Giants on South Manitou Island, but this tree possesses power. A twisted trunk with several protruding, ragged, burls appears eternal.  Looking skyward through its branches that are as big around as my legs, the lower ones long dead but the upper ones green, giving it life, I understand how some cultures can worship individual trees. Standing, as it does, among its many much smaller kin, this mammoth seems all the more dominant. Someday, in better light, I will revisit this tree but I will never capture its strength in a photographic image.
Copyright 2014 by Donald Drife

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Seeking Survivor Ash Trees

Researchers at the Northern Research Station of the United States Department of Agriculture are looking for naturally occurring Ash trees (Fraxinus spp.) in southeast Michigan. They are searching for a strain of Ash that will survive attacks from the Emerald ash borer (EAB), (Agrilus planipennis). The tree must be part of a native stand, have a healthy canopy, and be larger than 10 inches diameter at breast height (DBH). More information can be found at the USDA website. The ten target counties in Michigan are: Ingham, Livingston, Oakland, Macomb, Jackson, Washtenaw, Wayne, Hillsdale, Lenawee, and Monroe.

Ash trees can be identified even in the winter. Ashes have their buds in pairs (Opposite) and most Michigan tree species have single buds (Alternate). Maples, Ashes, Dogwoods and Horse-chestnuts (MAD-Horse) are our only tree species that have opposite buds. See my earlier post on identifying these trees.

Cottonwood,Ash, Basswood bark

Cottonwood-L Ash-C Basswood- R

Sassafras, Tuliptree bark

Sassafras- L Tuliptree- R

Mature Ash bark is gray with fine, broken, ridges. Ashes have opposite buds and opposite branches. When you look at the branch pattern on a tree look at the overall pattern. An opposite branched tree will always have a few alternate branches where it has lost branches. Young Tuliptree bark is similar but the ridges are not as deep and the buds and branches are alternate. Eastern Cottonwood bark is similar to Ash bark but it has larger ridges and is alternate branched. Sassafras bark has deeper ridges than Ash and often a reddish cast. The ridges on Basswood bark are not parallel.

Fraxinus quadrangulata

Blue Ash showing winged stems

Euonymus alata

Winged Euonymus buds and twigs

Pumpkin Ash (Fraxinus profunda) and Blue Ash (F. quadrangulata) are rare trees in Michigan. Blue Ash has a winged stem and the leaf scars meet. It resembles Winged Euonymus (Euonymus alata) but Euonymus has distinct bud scales, normally green twigs, and is never a large tree.

Fraxinus terminal buds

Ash Terminal Buds

Red and Green Ash are the same species (F. pennsylvanica). Red Ash is just a hairy form of the Green Ash. They have lateral buds that touch the terminal bud and the lateral buds sit in a small notch in the leaf scar. White Ash (F. americana) has a long terminal bud and the leaf scar encircles approximately half of the lateral bud. Black Ash (F. nigra) has a short section of the twig protruding beyond the last pair of lateral buds. The lateral buds are almost black and sit on the leaf scar.

Fraxinus lateral bud scars

Ash lateral bud scars

If you are hiking this winter in southeast Michigan, keep an eye out for large, healthy, Ash trees. Report your sighting to the USDA website mentioned above and aid in this valuable research.

Copyright 2014 by Donald Drife

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Juneberry: the “Dogwood” of the North

Amelanchier Juneberries

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.

Amelanchier  Juneberry blossoms and new leaves

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.

Amelanchier Juneberry blossoms and new leaves

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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Michigan Pines

Pinus strobus banksiana resinosa sylvestris

Pine needles: l-r White, Jack, Red (Black similar), Scots

Michigan has three native species of Pine trees and two widely established non-native species. Two additional species have been recorded in the Michigan Flora database but currently they rarely escape. They are Pitch Pine (Pinus rigida) and Ponderosa Pine (P. ponderosa). Both of these species have needles in groups of three.

Pinus strobus White Pine

White Pine

White Pine (P. strobus) is native and easy to recognize with its needles in groups of five. They are fine, soft needles. Its cones are three times as long as they are wide. This is the state tree of Michigan. This was the preferred pine species during Michigan’s lumber era, because it occurred in pure stands and floated well.

Pinus banksiana cones

Jack Pine: Pollen cones l, Seed cones r

Jack Pine (P. banksiana) is native occurring mostly north of Saginaw but coming south along the Lake Michigan coast to the state line. It has two, 2-4 cm (3/4” to 1 1/2”) long needles in each cluster. They are normally twisted. Its bark is dark red to dark gray and at times looks as if it is covered by burnt corn flakes. Bent cones are another distinguishing character of this tree. It is often stated that fire is required to open the cones but I commonly see open cones hanging on trees.

Pinus banksiana Jack Pine

Jack Pine

It is among young Jack Pines that Kirtland’s Warblers nest. This is a short-lived species; a sixty year old Jack Pine is ancient whereas a sixty year old Red or White Pine is still a teenager. Jack Pine is normally a small tree, reaching 15 m (50 feet) in height. I watched one Jack Pine for a decade that crept along the ground, never reaching more than 1 m (3 feet) in height but becoming 5 m (16 feet) long before it died.

Pinus banksiana l_Pinus sylvestris r

Jack Pine background left, Scots Pine foreground left and right

Pinus sylvestris  Scots Pine

Scots Pine

Scots Pine or Scotch Pine (P. sylvestris) is a Eurasian species that has been planted extensively in Michigan. Mature trees have a distinct reddish-orange bark in the upper tree trunk. The needles are similar to Jack Pines making immature trees difficult to separate. I hit my palm against the end of the needles and if they feel sharp then it is a Scots Pines. The needles are sometimes glaucous (with a waxy bloom) and tend to be slightly longer than Jack Pine needles. Cones on Scots Pines are straight and open in the second year.

Pinus nigra bark l P. resinosa c P. resinosa r

l-r Black Pine bark, Red Pine bark, Red Pine branch and cone

Red Pine (P. resinosa) is a native growing mostly north of Flint. It has two, 10-15 cm (4” to 6”) long needles in each cluster. When bent the needles break. This species has reddish-brown winter buds. Its common name comes from the flaky, reddish upper bark. Stumps, 110 years old, dot the field at our cabin near Grayling. Red Pines normally occur in mixed stands with Oaks (Quercus sp), Cherries (Prunius sp) or White Pine. They were lumbered later than the pure stands of White Pine.

Pinus nigra l P. resinosa r winter bud

Terminal buds l-r Black Pine (with first-year cone), Red Pine

Pinus nigra l P. resinosa r

cones l-r Black Pine (turned upside-down to show prickle), Red Pine

Black Pine or Austrian Pine (P. nigra) is an European species that is widely planted in the Great Lakes Region. The needles are similar to Red Pine but they are flexible. This species has black bark and appears denser having more needle clusters and branches than a Red Pine. Its winter buds are whitish and sticky. Black Pine cones have prickles on their umbos and Red Pines have flattened umbos. An umbo is the shield-like structure on a pine cone’s scale. Black Pine cones are yellowish-green before they open.

Pinus nigra  Black Pine

Black Pine

Copyright 2014 by Donald Drife

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