Stihl Helmet

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Unsafe tree work in our parks

Kirklevington Worker
LFUCG worker cutting black locust with no safety equipment. Cell phone photo.

While walking through Kirklevington Park, I saw two groups of Lexington city workers doing their jobs. On one side of the street, a group of solid waste workers were collecting trash. They were wearing high-visibility safety vests, helmets and work boots. On the other side of the street, several Parks & Recreation employees were cutting up a storm-damaged black locust. One worker was using a chain saw, while wearing shorts, casual shoes, and no safety equipment. The contrast was striking.

Tree work is inherently risky.  A chain spinning at high speeds can cut deeply into unprotected flesh and the resulting injuries can be horrific. In 2012, 243 workers died while engaged in tree trimming and clearing. In 1999, 28,500 people were injured while using chainsaws, and the number has been increasing ever since.

The average injury incurs more than $12,000 in medical bills. Medical costs for chainsaw injuries are at least $350 million per year. Workers’ compensation costs are at least $125 million.  In addition to obvious injuries, improper use of chainsaws can result in  hearing lost and nerve damage.

These injuries and costs are entirely unnecessary. Chainsaw manufacturers such as Stihl have greatly improved the safety of their products, including the use of anti-kickback chains, safety brakes and ergonomic positioning of handles.

Stihl Helmet
Helmet with face and ear protection for chainsaw operators can prevent eye, face and hearing damage.

Personal protective equipment (PPE) further decreases the risk of chainsaw use.  Safety helmets with eye shields and ear protection, chainsaw chaps and boots to protect legs, and gloves for hand protection can nearly eliminate the risk of chainsaw use if used properly.  In most European countries, where use of PPE is enforced and insurance coverage can be declined if PPE is not used properly, injury rates are a fraction of those in the US.

The use of safe chainsaws and proper PPE is useless without operator training and enforcement of safety rules by employers. I suspect that the employee in the photograph had access to PPE but chose not to use it.

Failure to use proper safety procedures and equipment is a risk to employees, but it is a greater risk to city government and ultimately to taxpayers.  Lost work time, medical expenses and the potential for legal action are avoidable.

The city should not merely require the wearing of PPE, but should implement a safety training program, along with rules and procedures that are enforced. There are consulting firms that specialize in safety training and equipment for tree workers. This approach is clearly working for the solid waste workers.

For more information, see The Risks and Rules of Chainsaw Operation in Incident Prevention Magazine.

American sycamore leaves

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American Sycamore: A Crown Fit for a King

Just north of the charming downtown district of Lebanon, OH, an area with well-known buildings and historical markers spanning over two centuries, a different kind of historical marker recently caught my eye. In the expansive front lawn of an elementary school building, I beheld two massive American sycamores towering over the manicured lawn.
As any good tree measurer would do, I pulled out my laser rangefinder and headed in the direction of the trees. While slowly approaching and becoming enveloped by the intermingled crowns of the wide-spreading trees, it became apparent that the crown spread on one of them was truly superlative. The tree closest to the school boasts a maximum crown spread of 145 feet, with an average crown spread of 134 feet – the largest crown spread of any species that I have personally measured.

What exactly is crown spread and how is it measured? From the American Forests Measuring Guidelines Handbook: “Crown spread is the horizontal separation of two points on opposite sides of the crown.” Imagine an outline of a tree’s crown projected downwards onto a horizontal plane. A line connecting the two points farthest away from each other represents the maximum spread. The simple 2-axis method can be used to find average spread by taking an additional spread measurement that is perpendicular to the maximum spread, and averaging the two measurements. The above-referenced American Forests handbook has excellent explanations of the 2-axis method and the more precise spoke method.

I’ve seen photographs and heard of other wide-spreading American sycamores scattered across the Eastern United States, but I didn’t have a full grasp of just how big the spreads can be. To find out, I reached out to fellow members of the Native Tree Society, the nation’s foremost collection of tree measuring experts. After seeing the measurements for some of the most famous American sycamores across the East, I’m beginning to think that the tree in Lebanon may even still yet have some room to grow! Here is a sampling of American sycamore spread measurements from the Native Tree Society. Some of these trees have experienced crown loss since the time of the measurement.

[table id=3 /]

It’s clear that the American sycamore, when given the chance, can attain great dimensions and truly has a crown fit for a king. Have you seen a wide-spreading American sycamore near you? If so, we’d love to hear about it!

American sycamore
American sycamore, Platanus occidentalis, in Lebanon, OH. Photo by Matt Markworth
American sycamore leaves
American sycamore leaves. Photo by Matt Markworth

Bur oak, Quercus macrocarpa, at St. Joseph Medical Center parking garage.

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Great Trees of the Bluegrass

Today, we are launching a new project “Great Trees of the Bluegrass” to locate and identify important trees in our region. We have a new Facebook Group: Great Trees of the Bluegrass for you to contribute your own observations, and we are also creating a new web-based identification and mapping tool for your use. The purpose of this project is to identify, map and evaluate the important trees of the Bluegrass and to tell their stories. We will later be extending this to the Nashville Basin.

The Great Trees are based on my book Venerable Trees: History, Biology and Conservation in the Bluegrass. The Bluegrass is home to the largest number of ancient hardwoods – trees that predate the existence of Lexington, of Kentucky, and even of the United States.

The criteria for listing Great Trees of the Bluegrass are: 1) the tree should be native to the Bluegrass; 2) the tree must be publicly available – either on public property or accessible to the public; 3) the tree must be old and large – we will start with a minimum of 100 inches circumference (32 inches diameter). Of course, we don’t know how old most of these trees are, but we can recognize the very old ones that are likely to predate the establishment of Lexington in 1779.

To get us started, here are 10 of Great Trees of the Bluegrass. Each tree will eventually have its own page. For now, the link will show you a larger version of the photograph.

The Ingleside Oak on Harrodsburg Road near Red Mile

The Ingleside Oak
The Ingleside Oak

The St. Joe’s Oak

The St. Joe's Oak
The St. Joe’s Oak

The Henry Clay Basswood

American basswood (National Champion), Lexington Cemetery
American basswood (National Champion), Lexington Cemetery

The Castlewood Park Giant Blue Ash

Blue ash in Casltwood Park.
Blue ash in Castlewood Park.

The Kissing Tree at Transylvania University

The Kissing Tree at Transylvania University
The Kissing Tree at Transylvania University

The Coldstream Bur Oak

The Coldstream Oak
The Coldstream Oak

The Veteran’s Park Oak

The Veteran's Park Oak
The Veteran’s Park Oak

The Kirklevington Oak

The Kirklevington Oak
The Kirklevington Oak

The Old Schoolhouse Oak

The Old Schoolhouse Oak
The Old Schoolhouse Oak

 

 

 

 

 

 

 

a chair

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Under the spreading chestnut tree

A red buckeye, close relative of horsechestnut
A red buckeye, close relative of horsechestnut

Many of us learned the great Henry Wadsworth Longfellow poem The Village Blacksmith in school, which begins:

UNDER a spreading chestnut tree
The village smithy stands;
The smith, a mighty man is he,
With large and sinewy hands;
And the muscles of his brawny arms
Are strong as iron bands.

As a forestry student, I learned that this tree was thought to be a horsechestnut, Aesculus hippocastanum,  not an American chestnut, Castanea dentata, though I never knew for sure.

A very good story in the National Geographic by Rebecca Rupp tells us of the history of American chestnut as a food source, and of work under way at SUNY ESF, my alma mater,  to revive the American chestnut through genetic engineering.  This is important work and I am glad to see it covered so well in the National Geographic.  The story begins:

“Perhaps the most quoted line about a chestnut tree in all of American history is Henry Wadsworth Longfellow’s “Under the spreading chestnut tree/The village smithy stands” from “The Village Blacksmith.” In 1842, when Longfellow penned his poem, the American chestnut (Castanea dentate) was in its prime.”

a chair
Henry Wadsworth Longfellow’s chair, made from the horsechestnut that shaded the village smithy. Source: public domain.

That got me to wondering which story was true -was it a horsechestnut or an American chestnut?  I did a little research, and to my astonishment found that Longfellow himself provided the answer. In 1879, a journalist named Ira Emory Forbes wrote Longfellow an impassioned letter pleading with the great poet to relieve him of his anxiety, saying:

“..the poem has always been of so much interest to me that I can not bear to think of my ideal being mutilated, the tree being the horse chestnut, instead of the graceful tree of our woods and hillsides”

Longfellow replied on April 18, 1879 referring both to the tree and to a chair that was made for him from the wood of the “spreading chestnut tree’ when it was cut down.

Dear Sir,

I am sorry to dispel an innocent illusion, but truth forces me to say, that the tree, which over-shadowed the village smithy, and of whose wood the birthday chair is made, was a horse-chestnut.

Yours very truly

Henry W. Longfellow

I think we have to accept the words of the great man himself.  The village smithy lay under the shade of a large horsechestnut.

Source:  The Letters of Henry Wadsworth Longfellow

Here is the entire poem, which is still a marvel:

The Village Blacksmith

UNDER a spreading chestnut tree
The village smithy stands;
The smith, a mighty man is he,
With large and sinewy hands;
And the muscles of his brawny arms 5
Are strong as iron bands.

His hair is crisp, and black, and long,
His face is like the tan;
His brow is wet with honest sweat,
He earns whate’er he can, 10
And looks the whole world in the face,
For he owes not any man.

Week in, week out, from morn till night,
You can hear his bellows blow;
You can hear him swing his heavy sledge 15
With measured beat and slow,
Like a sexton ringing the village bell,
When the evening sun is low.

And children coming home from school
Look in at the open door; 20
They love to see the flaming forge,
And hear the bellows roar,
And watch the burning sparks that fly
Like chaff from a threshing-floor.

He goes on Sunday to the church, 25
And sits among his boys;
He hears the parson pray and preach,
He hears his daughter’s voice,
Singing in the village choir,
And it makes his heart rejoice. 30

It sounds to him like her mother’s voice,
Singing in Paradise!
He needs must think of her once more,
How in the grave she lies;
And with his hard, rough hand he wipes 35
A tear out of his eyes.

Toiling,—rejoicing,—sorrowing,
Onward through life he goes;
Each morning sees some task begin,
Each evening sees it close; 40
Something attempted, something done,
Has earned a night’s repose.

Thanks, thanks to thee, my worthy friend,
For the lesson thou hast taught!
Thus at the flaming forge of life 45
Our fortunes must be wrought;
Thus on its sounding anvil shaped
Each burning deed and thought!

 

 

Kirklevington Oak Seasons_0000_May 31-Edit

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New leaves on a defoliated bur oak

A couple of weeks ago, we told you about a magnificent, ancient bur oak that was suddenly defoliated overnight.  We said that it would recover quickly and that we would update you. With 10 days of mild weather, the tree has leafed out very quickly.  Most trees maintain large reserves of starch and protein in their stems, and they can quickly mobilize the stored material to make new leaves.  Here are a couple of before and after pictures.  The upper picture is the tree on May 21, right after it was defoliated. The lower picture is the same tree on May 31, showing how quickly the tree has leafed out.  We still haven’t found the culprit, but this old tree does not seem to have suffered from early spring defoliation.

Defoliated bur oak
The Kirklevington Oak on May 21. There are very few leaves on the tree after defoliiation the night before
The same tree on May 31, 10 days after defoliation. Notice the new leaves growing quickly.
The same tree on May 31, 10 days after defoliation. Notice the new leaves growing quickly.
Dead white ash

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Dead Trees and the Great Curve

Dead ash trees
Dead white ash in a suburban neighborhood. These trees were alive in 2014.

This is the year of death in central Kentucky.  The emerald ash borer has been slowly expanding its population, and has now reached the point of mass destruction. You can see dead and dying trees all over town, most of which have died this spring.  From here on, barring some miraculous change in ash borer populations, the fate of the remaining ash trees is sealed.

Ash tree mortality
Simulation of the death of ash trees in Lexington, KY. First mortality was seen in 2009. Assuming the beetles were already present for 10 years, the curve shows that in 2015 (red arrow), we have entered the grand phase – the time of steep increase in tree death. At this rate, we would expect most untreated trees to be dead by 2025.

This is a predictable outcome of a biological phenomenon called the Great Curve of Growth. Mathematically, the Great Curve follows a logistic equation.  It works like this:

  1. At first, ash borer numbers are very small and few trees die even as the borer population increases.  This is called the lag period. Typically, the presence of the beetle is not observed for about 10 years after they arrive in an area.
  2. As beetle numbers increase, an explosion of death takes place, increasing steeply. This is the logarithmic phase. We are early in the logarithmic phase, and each subsequent year will bring approximately a doubling of the number of dead trees.
  3. Eventually, the beetles have killed most of the trees, and only a few live trees remain to be attacked. This is the stationary phase and ends with the elimination of white and green ash.
Dead white ash
A white ash that died in the Spring of 2015 from emerald ash borer

We can conclude from this analysis that the next few years will see an explosion of dead trees. Is there anything that can stop this explosion of tree death.  Yes.

  1. Weather changes, especially extremely cold winters, could slow the beetle. However this beetle has thrived in the cold of Michigan, so this is unlikely to happen;
  2. Predators and pests of emerald ash borer could increase in populations and lower the population of beetles. This would slow the rate of death of trees.  There are programs to releasepredatory wasps, but they are probably too little, too late.
  3. Treatment of trees is a known method to preserve important trees.  The cost of treatment has gone down and treatment is affordable for more landowners. Contact a certified arborist for more information.  In spite of the success of treatment, it is not possible to treat the majority of trees even in urban areas.  Treatment should be focused on large or important trees.
  4. Blue ash trees appear to be resistant. Our large population of blue ash trees are probably, but not certainly, safe.
Dead white ash trees
A dead white ash stand in suburban Lexington. These trees were alive in 2014.
New leaves on an old bur oak

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Defoliation of a bur oak – Overnight!

You may recognize the bur oak in this page from previous photos. It is a magnificent, ancient bur oak in Kirklevington Park.  I visit it often.  Last week I was looking at the tree in the late afternoon and noticed a few leaf fragments on the ground. The next morning, I came back and saw that the tree had been totally defoliated overnight, stripped of nearly every leaf. After a few days, it began to refoliate – to produce a new crown of leaves.  Spring defoliation is very common, but is not very harmful to hardwood trees.

None of the nearby bur oaks were defoliated. Two Shumard oaks had lost a little bit of foliage. It was like a special forces strike on a single tree. Remarkably, the defoliating insects were completely gone by morning, not a sign of them. I don’t know what they were.

We’ll add more pictures as recovery continues.

Click pictures to enlarge or for a slide show.

91yuIKqMxBL

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Favorite Tree Books

What is your favorite tree book?  We are creating a list of all the best books about trees.  Whether field guide or fiction, art book or paperback, tell us what tree books are important to you.  We will accumulate the list from your Facebook comments (you can post to Facebook by scrolling down on this story, or go to the Venerable Trees Facebook Page or the Native Tree Society page).

Be sure to tell us why this book is important to you, and provide the title, author and genre (field guide, fiction, etc.).  Provide a link to a source for the book if you can.

Our goal is not to create a comprehensive list of tree books but to understand what makes a tree book important to each of us.

I’ll start:

I began studying forest biology at the College of Environmental Science and Forestry, Syracuse, with the intention of becoming a wildlife ecologist. My first semester, I took Dendrology, for which the textbook was Harlow and Harrar’s Textbook of Dendrology.  Moosewood Bill Harlow was still working at Syracuse, but was no longer teaching.  My first weekend at Syracuse, I got the textbook from the University bookstore and began reading it. I did not stop until Sunday afternoon, having read it cover to cover.  That weekend changed the path of my career. By Monday morning, I had declared a forest botany major and went on to earn my PhD in forestry and botany at Wisconsin.  I have been a forest botanist and tree physiologist ever since.  I still have the Textbook of Dendrology in one of its newer editions.  Textbook of Dendrology, William Harlow and Ellwood Harrar, 5th edition, 1969. McGraw Hill.  (9th edition is currently available).

There are plenty of other tree books that have been important to me, and I’ll add some of them later.

bur oak

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World Tree Story by Julian Hight

We need more great books about trees, don’t we?  Here is your chance to help a fine author and passionate tree person to publish his next book, World Tree Story.

Julian Hight is an author, designer, photographer and musician. His very fine book Britain’s Tree Story has a prominent place on my bookshelf. In that book, he tells stories and recounts the history of many of Britain’s most significant trees.  Now, Julian is going worldwide, collecting stories about important trees all over the world. He is self publishing the book, and I am confident that it is going to be every bit as good as his first book. Check out the video below and consider contributing to Julian’s Indiegogo campaign to support publication of the book.

World Tree Story – Indiegogo campaign from Julian Hight on Vimeo.

Showy flowers

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Flowers, Pollen and Allergies

Is that tree causing your allergies?  That pretty tree with the white flowers?  That pine tree covering your car in green film?  Nope. It’s the trees you don’t see that are getting you.

This is the height of allergy season. You can feel it in your sinuses and see it on your car windows. Huge amounts of pollen are flying through the air, seeking out female flowers with which to mate. There are many misconceptions about pollen, tree flowers and allergies.

In my experience, many people are confused about what trees cause allergies. The beautiful showy flowers of spring trees like black locust or flowering crab are not the cause of allergies. These flowers are designed to attract insects, hummingbirds and other pollinating animals. They do not toss their pollen into the air, but wait for animals to carry pollen from tree to tree.

It is the tree flowers we don’t notice that are the culprits. Oak, Osage-orange, hickory, and lots of other trees produce long male flowers called catkins that drop huge amounts of pollen into the air. You may not notice the flowers, but your respiratory system does.

Pine, spruce and other conifers don’t produce flowers, but they do toss huge amounts of pollen into the air. However, their pollen is so large that few people have problems with conifer allergies.

So, if you have to curse at a flower this spring, don’t pick on the pretty ones.

Showy flowers do not cause allergies
Showy flowers do not cause allergies
Mature black locust at a horse farm, Fayette County

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In Praise of Black Locust

All over Kentucky, there is an explosion of the amazing white flowers of black locust, Robinia pseudoacacia. This is a tree that is both loved and hated. While it is in flower, I thought we’d take a few moments to talk about the virtues and sins of black locust.

Here are the things we love about black locust:

  • We love its flowers. Everyone in black locust country raves about the beautiful white clouds of flowers and the intense, sweet fragrance. I personally think it is the best-smelling flower of all.
  • Bees love its flowers. Beekeepers usually allow clover and locust honey to be mixed. However, in years when locust flowers before clover, it is possible to harvest a large quantity of the palest, clear, intensely sweet honey ever.  The years when I have been able to keep the locust honey flow separate from the clover have been my favorite beekeeping years.
  • Black locust is a nitrogen-fixing pioneer tree on disturbed sites. It will colonize cut banks, abandoned coal mines and other very poor sites and enrich the soil for other species.
  • For early settlers, it was a tremendously important timber source for masts, tool handles and fences. The hard, decay-resistant wood was prized.
  • Black locust is now the most widely planted North American tree in the world. It has been planted all over Europe, temperate Asia and southern Africa. It is used for livestock fencing, fuel and tool handles.

Here are the things we hate about black locust:

  • Black locust is impossible to get rid of. If we cut down a tree in our yard, sprouts will come up for decades.
  • It takes over pastures very quickly and is hard to control.
  • The sharp little spines hurt!  I got one buried in my head while clearing fields in North Carolina when I was a kid and I still have a little bump in my head.
  • It is invasive. Black locust is regarded as a nuisance or invasive tree on every continent except Antarctica.

 

 

[envira-gallery id=”3268″]

Bees on male bur oak flowers

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Bees on Bur Oak

For the last 10 days, I have watched an amazing phenomenon that I have never seen before. Oaks are wind pollinated. Occasionally we see insects visiting, but only casually. However, one bur oak that I keep an eye on has been abuzz with activity. Every day while the male flowers were open, there was a constant movement of bees. I saw several species, but only one was large enough to photograph readily. This large bee, about half the size of a honeybee, was abundant and working hard, with full pollen baskets.

What do you think? Have you ever seen this before?  Comment below (Facebook) with your observations

A few other observation:  The bees were not working other nearby bur oaks.  There were lots of other trees and shrubs nearby with showier flowers but they were not as heavily visited and did not have the same bees.

And now the big question – are these bees robbing pollen, or are they actually pollinating this bur oak?

Bees on male bur oak flowers
Bees on male bur oak flowers
Bees on male bur oak flowers
Bees on male bur oak flowers
Bees on male bur oak flowers
Bees on male bur oak flowers
Bees on male bur oak flowers
Bees on male bur oak flowers

Picture of Sherlock Holmes

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Sherlock Holmes, Dendrologist

The novels and stories about Sherlock Holmes by Arthur Conan Doyle are filled with keen observations of the world around him. I have read Sherlock Holmes repeatedly since I was a kid. Today, I find that Sherlock Holmes stories help me focus my own writing on details and precise observations.  Recently, in reading Holmes once again, I was struck by how often there are discussions of trees, usually in passing but sometimes central to the story.  In reading The Musgrave Ritual, I found this striking use of trigonometry for the measurement of trees, and it reminded my of all my friends in the Native Tree Society who are devotees of measuring trees. Here is the passage from The Musgrave Ritual:

Sherlock Holmes
Jeremy Brett as Sherlock Holmes.

“It was perfectly obvious to me, on reading the ritual, that the measurements must refer to some spot to which the rest of the document alluded, and that if we could find that spot, we should be in a fair way towards finding what the secret was which the old Musgraves had thought it necessary to embalm in so curious a fashion. There were two guides given us to start with, an oak and an elm. As to the oak there could be no question at all. Right in front of the house, upon the left-hand side of the drive, there stood a patriarch among oaks, one of the most magnificent trees that I have ever seen.

“‘That was there when you ritual was drawn up,’ said I, as we drove past it.

“‘It was there at the Norman Conquest in all probability,’ he answered. ‘It has a girth of twenty-three feet.’

“‘Have you any old elms?’ I asked.

“‘There used to be a very old one over yonder but it was struck by lightning ten years ago, and we cut down the stump,’

“‘You can see where it used to be?’

“‘Oh, yes.’

“‘There are no other elms?’

“‘No old ones, but plenty of beeches.’

“‘I should like to see where it grew.’

“We had driven up in a dogcart, and my client led me away at once, without our entering the house, to the scar on the lawn where the elm had stood. It was nearly midway between the oak and the house. My investigation seemed to be progressing.

“‘I suppose it is impossible to find out how high the elm was?’ I asked.

“‘I can give you it at once. It was sixty-four feet.’

“‘How do you come to know it?’ I asked, in surprise.

“‘When my old tutor used to give me an exercise in trigonometry, it always took the shape of measuring heights. When I was a lad I worked out every tree and building in the estate.’

“This was an unexpected piece of luck. My data were coming more quickly than I could have reasonably hoped.

“‘Tell me,’ I asked, ‘did your butler ever ask you such a question?’

“Reginald Musgrave looked at me in astonishment. ‘Now that you call it to my mind,’ he answered, ‘Brunton did ask me about the height of the tree some months ago, in connection with some little argument with the groom,’

Picture of Sherlock Holmes
Watson (David Burke) and Holmes (Jeremy Brett) in The Musgrave Ritual

“This was excellent news, Watson, for it showed me that I was on the right road. I looked up at the sun. It was low in the heavens, and I calculated that in less than an hour it would lie just above the topmost branches of the old oak. One condition mentioned in the Ritual would then be fulfilled. And the shadow of the elm must mean the farther end of the shadow, otherwise the trunk would have been chosen as the guide. I had, then, to find where the far end of the shadow would fall when the sun was just clear of the oak.”

“That must have been difficult, Holmes, when the elm was no longer there.”

“Well, at least I knew that if Brunton could do it, I could also. Besides, there was no real difficulty. I went with Musgrave to his study and whittled myself this peg, to which I tied this long string with a knot at each yard. Then I took two lengths of a fishing-rod, which came to just six feet, and I went back with my client to where the elm had been. The sun was just grazing the top of the oak. I fastened the rod on end, marked out the direction of the shadow, and measured it. It was nine feet in length.

“Of course the calculation now was a simple one. If a rod of six feet threw a shadow of nine, a tree of sixty-four feet would throw one of ninety-six, and the line of the one would of course the line of the other. I measured out the distance, which brought me almost to the wall of the house, and I thrust a peg into the spot. You can imagine my exultation, Watson, when within two inches of my peg I saw a conical depression in the ground. I knew that it was the mark made by Brunton in his measurements, and that I was still upon his trail.

sugar maple flowers

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More tree sex – sugar maple

sugar maple flowers
Sugar maple flowers, functionally male, in spring

Have you seen the sugar maples in flower?  In Kentucky, they are flowering right now, but you need to look closely to see them. The flowers are not very show, their pale green blending with the green riot that is spring.  These interesting flowers will reward the careful observer.  Sex in maples is complicated. Even though sugar maple flowers are perfect – they have both male and female parts – most of the flowers low on the tree, as in this picture, are functionally male – the female parts don’t work. High on the tree, the opposite is true, and many flowers are functionally female. For a wind-pollinated tree like sugar maple, this division of labor may prevent pollen falling directly on the stigmas of the same flower.  Maples are self-infertile, so the pollen of one tree can’t fertilize the flowers of the same tree.

We have lots of other articles about the fascinating biology of tree sex.

 

IngestMixedJuly09-1856

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A fastidious disease kills oaks and olives

All over central Kentucky, ornamental pin oaks are in trouble. They are slowly declining and dying, and looking terrible in the process.  From street trees to horse farms, thousands of pin oaks need to be removed over the next few years.  The primary cause is an odd species of bacteria, Xylella fastidiosa, that lives in xylem and plugs the xylem vessels, preventing the leaves from getting enough water. The trees decline due to water stress.  Xylella moves from one tree to another with the help of little insects called sharpshooters.

In Italy, olive trees are dying and threatening the important olive oil industry. The cause of this disease is the same bacterium, Xylella fastidiosa, carried by sharpshooters.  Xylella is probably not native to Europe, but may have been brought there by the international trade in horticulture. Industrial horticulture moves plants all over the world, and some of these carry deadly pests and pathogens.  Xylella also causes disease in Brazilian citrus, Georgia peaches and California grapes.

For the full story, see my column at Planet Experts:  A Fastidious Disease of Olives, Grapes and Shade Trees

Dead olive trees
Olive trees killed by xylella (Photo credit: Institute of Plant Virology Italy)
IngestMixedJuly09-1856
Pin oak killed by Xylella fastidiosa being felled in an urban neighborhood

 

Sycamore fruit in spring

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Sycamore in Spring

American sycamore (Platanus occidentalis) flowers in late spring and creates the well-known sycamore ball that kids are fond of throwing at each other (not quite as painful as sweetgum balls). The fruit is unusual because it stays on the tree all winter as a hard, dormant ball. The following spring, the ball begins to expand and soften, soon releasing thousands of feathered achenes – tiny fruits, each containing a single seed. These achenes can float long distances in the air or on the water, and quickly germinate when they find damp soil. (Note: Sycamore in North America is called plane-tree or buttonwood in the United Kingdom, while the word sycamore is used to refer to a maple, Acer pseudoplatanus. Confusing? That’s why Latin names are important.)

Sycamore flower
Sycamore, Platanus occidentalis, flower
Sycamore fruit in winter
Sycamore fruit in winter
Sycamore fruit in spring
Sycamore fruit in early spring, starting to expand
Sycamore fruit in spring
Sycamore fruit in spring, releasing tiny feathered achenes into the air.
Freshly cut grass

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The smell of spring

Freshly cut grass
Freshly cut grass releases volatile chemicals

On my walk yesterday, the world was filled with the smell of spring.  The smell of flowers and  barbecuing meat will be along soon enough, but early spring is dominated by the earthy fragrance after rain and the wonderful, evocative odor of new-mown grass.  Lawnmowers were whining away last weekend mixing the smells of new mown grass and damp earth.

Where do these smells come from, and is there a deeper meaning to these odors than just a pleasant spring fragrance?  Many of the wonderful smells of spring are of semiochemicals – chemicals produced by an organism that can affect the behavior of other organisms.

The new-mown grass smell is mostly from four closely-related six-carbon molecules that are produced by the breakdown of fatty acids. Together, they are called green leaf volatiles (GLV). As a cow or mower takes a bite of grass, these molecules are quickly produced by leaf enzymes and just as quickly evaporate. In pure form, each GLV has a pleasant, spicy fragrance, but it doesn’t remind me of the smell of new mown grass. It is the combination of the six-carbon molecules, and probably some others as well, diluted in the air, that combine to give us that wonderful smell.

Green leaf volatiles
Green Leaf Volatiles. 2-hexenal, 3-hexenal, 3-hexenol, 3-hexenyl acetate (top to bottom). Source: ChemSpider

It is what happens next that is quite remarkable. We are not the only creatures that can smell green leaf volatiles.  We can think of green leaf volatiles as alarms, warnings and invitations. Entire communities respond to the GLV chemicals wafting through the air.  For nearby plants,  GLV is the equivalent of Tolkein’s Horns of Buckland sounding “Awake, Fear, Fire, Foes, Awake”  and plants that smell the GLV immediately mobilize their defensive chemicals to ward off herbivores. I use “smell” here in the sense that receptors in the plant detect the chemicals, just as receptors in our nose do.

Insect herbivores that want to eat the plant can also smell the GLV.  To them, it may say “someone is already eating this plant,” and they will lose interest and go elsewhere. Other insects may be attracted by GLV. For a predatory or parasitic insect looking for another insect to eat, the odor says “Hey, there are bugs eating a plant, c’mon over.”  Many wasps, for example, are attracted to GLV and will attack insects that are eating the plant. So in two ways, GLV act as plant defenses: they tell nearby plants to prepare for herbivores, and they tell nearby predators and parasites to attack the herbivores.

So, while you are smelling the wonderful odors of new-mown grass, there is an entire community of plants and animals that are responding to the GLV.

And what of the earthy smell?  That is another interesting story of chemical communications.  Earthy fragrance comes from several sources, but the two major odors are geosmin and 2-methylisoborneol (2-MIB). Geosmin is made by an important group of soil bacteria in the genus Streptomyces. You may recognize that name as being related to the antibiotic streptymycin, and in fact many antibiotics come from soil bacteria. Geosmin and 2-MIB are also associated with poor-quality water and wine.

What might geosmin communicate to other organisms?  Prof. R. Meganathan suggests that geosmin might be a cue to the availability of water. Camels

Geosmin
Geosmin

are thought to be able to smell water in an oasis from 50 miles away. Since water has no smell, it may be the geosmin that lures the camel. What does that do for the Streptomyces?  Camels drinking from an oasis might carry the bacteria from one oasis to another. Of course, this is one of those Just So Stories that is hard to validate. In humans, geosmin may warn us of low-quality water or wine. The smell is often associated with fish raised in aquaculture ponds, but it can be eliminated by rinsing with lemon juice, which breaks down the geosmin.

As you take your spring walks and inhale that heady mixture of damp soil and new-mown grass, look around and think of all plants, insects and other creatures that might be sniffing the air as well.

Quercus macrocarpa-7276-Edit

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Death of a Venerable Tree

The Venerable Trees of the Kentucky Bluegrass are extraordinarily long-lived.  This past weekend, we lost one of the largest and oldest bur oaks in the region.  The tree, at the corner of Versailles Road and Man O’War Boulevard on a farm, fell to the south.  The death of this tree was most unusual. It was a huge and vigorously growing tree, and it simply fell over.  Here is a preliminary analysis of what might have caused this tree to fall over.

Although this tree was ancient, it is rare for Bluegrass trees to simply fall over.  More commonly, trees decline slowly after lightning strikes, or following soil compaction and mower damage. Of course, the most common cause of death is the bulldozer – development has decreased the population of bur oaks in Fayette County by over 90% in only 60 years.

I examined this tree as did Master Arborist Dave Leonard, and there are some clues to why this tree fell over.  The conclusions are mine, but Dave pointed out several features of significance.

The most important clue is the exceptional  weather just before the tree fell  (weather data from a station <1 mile from the tree):

  • From April 2 to 3, we had 6.40 inches of rain, including 5.17 inches in 24 hours, a record;
  • Sustained winds from April 2 to 5 were 16 to 36 mph, with gusts of 47 mph on April 2 and 36 mph on April 3 from N and WNW;
  • There were no tornadoes in the region, and no known microbursts. However, there is no nearby official Doppler radar and we cannot rule out a microburst.

The condition of the tree:

  • This is an exceptionally large tree, 15.96 ft circumference 10.5 feet above ground (it wasn’t possible to get a tape under the tree at 4.5 ft.) and tall, >92 ft.
  • The tree was growing vigorously and rapidly, which is common in our ancient trees. Lateral branches averaged 9 inches new growth in 2014.
  • The tree had a pronounced lean to the south. Such leans are common in ancient bur oaks in the Bluegrass.
  • The tree is remarkably sound. Although there does appear to be some heart rot, there are few signs of extensive decay. We will know more when we dissect the tree.
  • Structural roots (the major woody roots) on the north side of the tree are large and sound, with no decay. However, they broke off at 3-15 ft from the stem.
  • There was evidence of surface structural root damage on the south side of the tree from long-term mower damage.  We can’t yet see deeper structural roots on the north side because the stem is in the way. This is important because in heavy wind, these roots would experience strong compression.

My tentative conclusion is that the tree fell because 1) surface structural roots on the south side were heavily decayed due to long-term mower injuries; 2) the soil was saturated from prolonged heavy rainfall; 3) wind gusts from the north compressed roots on the south side, and the remaining south side roots were not sufficient to absorb all the compressive force; 4) as the compressed roots on the south side failed, the weight of the tree exerted enough tension on roots on the north side that these roots failed, even though they were not decayed.  We cannot, however, rule out a microburst that produced an intense force on the north side of the tree, compounded by the weakening of soil structure by heavy rain.

This is a preliminary analysis, and we will learn more as we dissect the tree.

Ancient bur oak
Ancient bur oak that fell in unusual weather.
Uplifted root system
Uplifted root system
base of the tree
Base of the tree with moderate decay . Note the pooled water in the pit.
damaged roots
Mower damaged (A) and undamaged (B) surface structural roots
structural roots
Major structural roots (starred) on the north side
Ashland-8931

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The Sap Is Rising

A drop of sap from a fresh cut on a sugar maple branch.
A drop of sap from a fresh cut on a sugar maple branch.

“The sap is rising” is an often heard description of early spring. If you cut into the stem or branch of certain trees – sugar maple, birch, hickory, walnut, or sycamore – on a cool spring day, you may see sap dripping from the cut end, or an icicle of sap forming.  The sap is slightly sweet and is the source of maple syrup. Yet if you cut a tree a few weeks earlier or later, nothing happens.  What is going on?

During the winter, when trees are dormant, the stems store large amounts of starch, a polymer made of long chains of glucose, a simple sugar. The starch is stored in living cells in the wood, called parenchyma. When nights are cold and days a bit warm, enzymes in the stem break down the long polymers into the simple sugar sucrose.  Suddenly, the number of molecules in the parenchyma cells goes from a small number of starch polymers to a huge number of small sucrose molecules. The sucrose creates an osmotic potential that causes water to flow into the parenchyma cells.  This is the simple and familiar principle of osmosis. As water moves into the cells, the pressure inside the cells rises. Some of the sucrose is pumped out of the parenchyma cells into the dead xylem cells. Water continues to flow from the soil, raising the pressure in the stem.  When a branch breaks or is cut, the pressure causes the sap to flow out.

Diagram of starch and sugar
When starch is converted to sucrose, water flows into the cell.

In maple syrup production, a metal spile is driven into the stem and connected to plastic tubing, allowing the sap to flow from the tree to the sugar shack. Maple syrup production is only commercially practical in places with the right weather – cold soil, cool nights and warm days.  The cool nights promote the conversion of starch to sugar, while warm, sunny days allow water to flow from the soil into the stem.

Icicle of maple sap
An icicle of maple sap

In Kentucky, where I live, commercial maple production is not practical. The spring tends to warm up rapidly and there is usually little snow to insulate the soil, making the sap flow season too short to make any money.  A year like 2015, though, could be a good sap year. I have already seen bleeding sap in a number of maple trees.

The positive pressure inside the stem lasts for only a few days to weeks.  Trees do not push water up the stem, they pull it from the top.  For the entire growing season, the stem is under strong negative pressure (<0).  Negative pressure is not something familiar in everyday life: it is not possible to create a pressure less than zero (a vacuum) in a gas. But it is possible in tightly constrained narrow columns of  water in the xylem of a tree.

In the best years for sap production, spring weather produces cold soil, cold clear nights and warm days. Sudden spring warming, as happens more frequently as climate change take hold, reduces sap yields.

chinkapin oak

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A visit to Oakland Farm

Measuring a tree
Doug Witt, Laura Greenfield and Tim Diachun measuring an old bur oak at Oakland Farm

If you go to Lexington or Paris farmers’ markets, you may know Oakland Farm, “Home of the $10 Tree”  Tim Diachun, our business manager, and I spent a wonderful afternoon at the farm with the owners, Doug Witt and Laura Greenfield.

Oakland Farm is not named for the trees they grow in their nursery, but for the absolutely spectacular woodland pastures that meander through the 700+ acre farm.  Oakland Farm is a multi-generation family livestock farm, in operation since 1876.  Last year, Doug and his niece Laura began a small tree nursery, growing seedlings of native Kentucky trees for the local market.  They are filling a very important market need for seedling trees, and we will have much more to say about that in the near future.  For now, we want to focus on the woodland pastures.

Many Bluegrass farms have woodland pastures of ancient trees that predate the settlement of the region.  What stands out about Oakland farm is not just the large number of trees but the incredible character of each one.  These trees are very old and have taken on the typical appearance of very old trees – gnarled branches, many of them broken, the stems often leaning because of shifts in the soil. Rather than just tell you about them, we’ll let you feast your eyes on them.

We really appreciate the enthusiasm of Doug and Laura both for their ancient trees and for their new tree nursery.  Our hope is the Venerable Trees and Oakland Farm are beginning a long and mutually beneficial relationship.

Scroll down to see more pictures of Oakland Farm’s amazing trees.

chinkapin oak
An ancient, gnarled chinkapin oak at Oakland Farm

 

bur oak
A leaning bur oak at Oakland Farm

 

kingnut
A beautiful kingnut at Oakland Farm
blue ash tree
Old blue ash on a hill at Oakland Farm
bur oak
Another one of Oaklands great bur oaks

 

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Hazardous street trees

Hazardous tree
Pin oak in decline at a busy intersection near power lines

Hazardous street trees can cause a huge amount of damage, including personal injury and property damage.  Here is an egregious example. This pin oak is at the intersection of Robin Road and Tates Creek Road. It is right next to the newly installed sidewalk and adjacent to a major power line.

The tree has been in decline for years due to bacterial leaf scorch, a vascular disease that infects many pin oaks in urban areas.  The tree has been dropping large dead branches for several years, and it is hard to believe that the property owner is entirely unaware that the tree is nearly dead.

Stem of declining pin oak
Declining pin oak with fruiting bodies of Biscogniauxia atropunctata

This tree has declined to the point that you can see the gray fruiting bodies of Biscogniauxia atropunctata.  In healthy trees, this fungus lives quietly and harmlessly in the bark. Once a tree begins to die, the fungus invades the phloem and sapwood and contributes to the trees quick death.

Should this tree fall, it could break the power lines or fall across one of the busiest streets in town. The tree needs to be removed before someone gets hurt.  Ultimately it is the property owner’s responsibility, but the danger is sufficient that the city and the utility may need to take action.

The sidewalks along Tates Creek were installed over the last couple of years and many trees were planted. This would have been a good time to assess the risks of the existing row of pin oaks along the road. It appears that this was not done.  All the pin oaks along this corridor are in decline because of leaf scorch, and should have been assessed and removed as part of the sidewalk and powerline project.  The cost of removing all these trees will now be much greater.

 

The Ingleside Oak

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Finding Left-Behind Trees

The Ingleside Oak
The Ingleside Oak

Finding left-behind trees can be the start of an urban adventure.  As our woodland pastures were developed into urban areas, most of the trees of woodland pastures were cut down. A few remained, usually as single trees in a parking lot or front yard.  Here’s where the adventure comes in: when we find a single tree and take some time wandering around, we often find more.

Tree near the Ingleside Oak
A bur oak behind the Ingleside Oak

So it is with the Ingleside Oak on S. Broadway in Lexington.  I have known this tree for many years, but only recently took the opportunity to wander the neighborhood near the tree.  The search was rewarded, as we found about a dozen trees representing the original woodland pasture trees of Ingleside Manor.

Clusters of trees are found in other areas as well. In Ecton Park are two old blue ash trees, but the neighborhood around the park has over a dozen trees in front and back yards.

Old bur oak in an abandoned lot
Old oak in an abandoned lot behind the Ingleside Oak

The next time you find a Left-Behind Tree, we hope you’ll take the time to look around for others. And be sure to tell us about them.

 

Spring 2014-8794-Edit

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Early Spring Trees

Sweetgum mixed bud containing flowers and leaves. The bud is swollen and the green on the bud scales show that it is growing and ready to 'pop'
Sweetgum mixed bud containing flowers and leaves. The bud is swollen and the green on the bud scales show that it is growing and ready to ‘pop’

You may feel we are in the throes of winter, but for many trees, it is already early spring. How can that be?

In the late summer, trees begin to enter a stage of deep sleep called dormancy. They don’t stop growing because it is cold, they stop growing because a combination of long nights and cold sets up a complex hormonal response. If you take a twig off a tree in late fall and bring it inside, giving it plenty of light, warmth and water, it will probably do nothing. It is not simply asleep, but dormant, and only one thing will wake it up – more cold.

By now, in most North Temperate regions, some trees have gotten enough cold to overcome dormancy. They are poised to begin growing as soon as the weather improved. Other trees are not ready yet – they need more cold to overcome the dormant state.

If you are a careful observer, you should begin to notice buds beginning to swell, bud scales changing color, and even a few trees beginning to show flower parts. These trees are ready for spring and only need a few warm days to begin growing. In my area, red maple, silver maple, and elms are ready to go.

If you don’t want to wait, try bringing some twigs inside. Set them in water like a flower arrangement, and see what happens over a few days. Some trees will do nothing – they are not yet ready and need more cold days. Oak, beech and hickory often require longer periods of cold. Other trees will pop in a few days.

Red maple, Acer rubrum, functionally female flowers
Red maple, Acer rubrum, functionally female flowers
Veteran Oak

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Veteran Oak – A Left Behind Tree

The Veteran Oak in Lexington is one of the most iconic trees in the city.  A magnificent bur oak, it lies along a popular walking path on the south side of town.  The Veteran Oak is a left-behind, the only ancient tree in a young riparian (stream-side) forest.  Most of the ancient left-behind trees are on dry uplands, like the Old Schoolhouse Tree. The Veteran’s Park Oak is on a stream bank and benefits from high soil moisture and intermittent flooding.

The tree is in excellent condition. It has a few dead branches and lost its top at some time. This is normal for very old trees, and the dead branches and hollows provide habitat for a wide range of animals and fungi.  Young trees around the old oak are beginning to grow into its canopy.  Sometime soon, in the next few years, we will need to thin the trees around the Veteran’s Park Oak to give its lower crown more sunlight.  This technique of removing smaller trees to concentrate growth on larger trees is called ‘thinning from below’, also sometimes called ‘haloing’, though I prefer the former term. The path that goes by the tree on the creek side is causing some soil compaction, and should be closed.

Here is a photograph of the entire tree. This is a composite of 36 individual photos stitched together.

Veteran Oak

 

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