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Norway Maple

Categories: Trees

I’ve been thinking a lot lately about one of the more contentious trees in our urban forest, the Norway maple. Late this fall, while the leaves were still turning, I recently closely inspected over ⅔ of our campus trees, looking for problems, and Norway Maple kept appearing in the problem lists, with similar patterns of failure.

Norway Maple-healthy young tree

Some would say this is to be expected. Norway maple has been an extremely overused plant in the North American landscape, a victim of its own success. 100’s of cultivars have appeared over the years, including one of the most popular shade trees, Crimson King Maple-what most former customers of mine would simply call “Red Maple”, for its dark red leaves all summer long.
John Bartram, one of the fathers of early American botany, introduced the Norway maple in 1756, after receiving seedlings from Philip Miller in England, and started selling them in 1762. The trees remarkable adaptability to varying site conditions, including a broad tolerance of soil texture and pH, made it a popular tree among early arborists and gardeners. And a knack for sending out sports made it one of the first trees to get cultivars selected from it.

Norway Maple,  Acer platinoides,  flowers attractively in the early spring, late April here, with clusters of yellowish green flowers appearing before the leaves, each flower about ⅓” in size, but held in large clusters called corymbs, completely covering the tree. Norways are actually one of the most attractive early flowering trees. Bright yellow fall color can frequently be seen, in years when Tar spot doesn’t decimate the crown foliage.

The flowers turn into large seed pods called samaras, with a pair of seeds held in the center, and large flat wings spreading to each side. Split in half, and each side will helicopter towards the ground slowly, or alight in a breeze and fly for some distance. The wings of the helicopter extend around the seed, and can be opened like a book, where the milky white sap inside can act like a glue, allowing the samara to be attached to one’s nose, where it can stay stuck until nap time.

This milky white sap is a great way for the confused to identify Norway maples, as the similar sized Sugar and Red (Swamp) maples have a clear sap when broken. Spend some time with them, though, and identification becomes easier. The bark is a dark gray, and is ridged and furrowed, unlike any native maple. The leaves are large and dark green, larger than any other maple around, and while similar to Sugar maple, are flatter at the base.

It’s the leaves that cause many of the problems of the species, a victim of their own success. The size of the leaves create a super dense shade, making growth for grass underneath nearly impossible, but also for any interior growth on the tree itself. All the leaves on a Norway maple, and therefore all the growth, is on the outside of the tree. This is a red flag in the tree structure world, where all the end weight of the tree, and all of the wind load, is not shared throughout the tree, but, being held at the ends of the branches, and can be prone to breakage. Fortunately, the wood is fairly strong, and failure is more often seen in bad branch angles. The bare interior of a Norway, though, to me, is as distinctive an identifying characteristic as anything else.

Trunk Failure from Bad Branch Attachments

The dark dense canopy from the leaves also aid in the invasiveness of the species. Norway maple has been outlawed for sale in southern New England, and will become so in Vermont in a couple of years. The shade tolerance, in addition to its own dense shade, and its shallow root system makes the tree a fierce invader in the forest ecosystem, out-competing native maples in the understory, and inhibiting native seedlings (Galbraith-Kent, S. L. and Handel, S. N. (2008), Invasive Acer platanoides inhibits native sapling growth in forest understorey communities. Journal of Ecology, 96: 293–302. doi: 10.1111/j.1365-2745.2007.01337.x) . The shallow roots also hinder the growth and development of native forest flower species.The tree itself hosts less native caterpillars than other native maples, and North American mammals don’t recognize the seeds as a food source.

Norway maple gets its name from the northern end of its native range, and the population extends through the Caucasus and Turkey. There, the tree flowers 3-4 weeks earlier than the similar Sycamore maple, and is thereby kept in check, as both trees are insect pollinated, but the earlier flowering means only 5-15% of the seedling forest population seems to be Norways. Normal longevity for the species only seems to be 100-150  years, although trees in it’s preferred habitat, the Balkan peninsula, lives to about 200.

Our campus trees seem to be failing all at about 100 years as well, for a variety of causes. As mentioned above, Norways seem to be prone to bad branch angles, where cavities form and cause holes in the branches and trunk. Another problem with the tree seems to be a propensity towards girdling roots-roots that circle around the trunk underneath the ground, choking itself off. Norways make up about 10% of our tree population, but account for more than that in shade canopy, so, while they are invasive, we clearly can’t actively remove them. Some younger trees are in front of Forest Hall along Route 125, as well as in front of Emma Willard. The largest specimen is on the north side of the Axinn Center, a tree held together by a jungle of cables up in the crown.

Over-Mature Norway Maple at Axinn

Why?

Categories: Trees

7-18-6.

Not a fertilizer label, but an accounting of the fall semester at Middlebury. Seven-the  number of weekends in a row we’ve seen vandalism against trees. 18-the total number of trees affected. And 6-trees killed outright.

We come into work Monday morning, and, in addition to picking up the inevitable and ubiquitous litter and detritus from the weekend, now survey the damage as well. I was not writing of it, hoping to sweep our problem under the rug, hoping that these acts were random, solitary, maybe just an aberrant mutation on an otherwise pristine campus, a passing social deviation that would go away on its own.

And I’m preaching to the choir, here, after all. I’ve discussed vandalism in the past on Middland, and am quite frankly a little sick of telling the tale. I’ve reported this problem to my superiors, and they’ve approached community council. And I was going to get on with life, and write posts on annuals, the Sustainable Sites Initiative, and put some more work into Turf Battle.

Last night, Dean Shirley Collado wrote a piece on One Dean’s View called Plates and Privilege. We’ve all heard about the missing plate problem, thanks to Aunt Des and the great communications department. But Shirley’s take is different, and had me thinking all night (well, until 9:30 or so, I can’t seem to stay up like I used to) about privilege. Let’s let her say it best:

I would like to call students to action to think more critically about the human face behind the dish problem. Think about what it says about us as a community when these small acts of thoughtlessness create a collective problem that impacts all of us in a negative way. This thoughtlessness speaks volumes about what kind of people our students are going to be when they leave this institution.

So, I thought, our tree vandalism is a problem of privilege, like the many beer cans scattered around on a Monday. It’s easy to take trees for granted, and yes, sometimes they do get in the way (I’ve wondered on one or two broken branches if the offender was tall-sick of running into the same branch every day).  But then I cleaned up some of the damage today, and came to a different conclusion.

We have a problem of violence.

Pictures won’t even do it justice, and even my words won’t. In the service building? Come by my office, I’ve saved a couple pieces of broken limbs. But let me try to explain what’s going on here.

The offender (I hesitate to use the word ‘student’, as surely this individual isn’t really learning anything here) is breaking limbs off of trees. Serious limbs. I climb trees, and, while I still resemble the pasty geek I was in high school, I’ve jumped a couple of weight classes. Limbs broken would hold me and my chainsaw with room to spare. Limbs that are not just snapping off, but need to be bent, wrenched, moved back and forth hoping to break 3” of bark and wood to separate it from the tree. Entire small trunks of immature trees not only bent to the ground, but shaken, trampled, twisted and torn, sometimes breaking completely, sometimes left hanging , or lying in ground, waiting for a chalk outline to surround it. This is an act of rage, of violence, well beyond wanton destruction of property, senseless passing violence against an animate object incapable of screaming or defending itself.

A 3” limb, counting rings, is probably very well older than the person breaking it off.

Monday will come again, and again we’ll go out, willingly pick up the remnants of a privileged life, but hope and pray that no more violence has befallen our silent friends.

Some Late Fall Color

Categories: Trees

We’re in the bitter end of fall here, at least in terms of foliage. To me, this is when trees really start to shine. Maybe it’s all the bare trees nearby, or the perpetually cloudy skies, but the remaining foliage seems to take on an extra glow, or maybe urgency. Foliage colors that wouldn’t have turned a head 2 weeks ago now looks spectacular in the dying season, like the russet brown of the Star Magnolia behind Voter Hall. Sunlight breaking through the clouds acts like a highlighter pen. The wet cold makes any color seem all the more special. Here’s a little slideshow of trees and some shrubs that turned my head late last week.

Strange Fruit Falling from the Moon

Categories: Trees

Osage Orange-fruit

Every year, people working in Facilities start bringing me these tennis ball sized fruit. Last year, I decided to have some fun, and started freaking people out, acting incredulous they were actually touching them, and insisting they go wash their hands immediately, or terrible things would happen. This year I’m pretending they fell off the moon, and just happened to roll down to the front of the auto shop.

The truth is almost as strange. Middlebury College is in posecession of Vermont’s largest Osage Orange tree, Maclura pomifera. The circumference of the trunk is only 40″, nowhere near the record tree in Virginia of 321″. Ours is under the shade of a large sugar maple, and sits at the top of Stewart Hill, where its tennis ball sized fruit promptly roll downhill, over the speed dip, and end up near all the equipment.

Originally native only to southern Oklahoma and northern Texas, the Osage Orange was introduced far out of it’s range by using it as fencing, as it’s thorns and brushy nature made great hedges to keep out cattle.   It met the demand of a hedge in the wild west , “horse high, bull strong, and pig tight.” I’ve chased a loose pig before. Pig tight is saying quite a bit.

Alas, it was not hedge clippers, but barbed wire that won the west, replacing Osage Orange in the 1880’s.  The edible (?) fruit is cherished by squirrels, but more commonly used as holiday decorations.  Some have described the fruit as “brain-like”. If my brain were only that large…Chemical compounds in the fruit repel insects, although the whole fruit itself does not. The fruit is anachronistic. Usually large fruit is a method of seed dispersal, but squirrels are notoriously finicky on that front. Some theorists state that an extinct Ground Sloth used to aid in the spread of the plant. Indeed, the fossil record shows a  much larger range to the genus than what we see now.

The wood itself is remarkably able to resist rot and decay-and has been used as railroad ties and pavement blocks, as well as a superior wood for bows (archery, not violins). A bright yellow dye can be extracted from the bark.

Osage Orange Bark

Horticulturists like some parts of the Osage Orange. It’s yellow gold fall color can frequently rate spectacular, and it also boasts a pretty orange brown older bark. Michael Dirr, expert on all landscape plants, says the fruit is “effective in September, and lethal in October if one is sitting under the tree” and states that one should “select male trees; the large fruits are a nuisance and a problem around public areas as people will invariably use them for ammunition”. Male trees are being selected, and cultivars developed for use as a street tree. The species is remarkably tough, able to grow nearly anywhere. One last thought-Osage Orange is dioecious. Male and female flowers appear on separate plants, and of course you need both to pollinate. So, while our clearly female tree still sets fruit, they are sterile. Large, but sterile nonetheless.

So ours sits, unremarkable most of the year, until the fruit starts rolling. I don’t know how it ended up planted there, or even where it was grown. I’ve never even seen one for sale.

New School Year, New Vandalism

Categories: Trees

Personally, I was hoping we were done with this. I’m as tired of writing of it as you are of reading.

Since the school year started, our landscape department has seen an additional 4 incidents of tree vandalism. One, a newly planted tree was broken in what appeared to be a climbing attempt (no, we’re sure it wasn’t a squirrel of exceptional size). An arborvitae was snapped in half in front of a dorm, and a random branch broken off a a large sugar maple in front of Johnson.

This is only half the tree!

The final straw, though, and the reason for the quick post on a lunch hour, was the near total destruction of a little red oak by the Davis Family Library. Nearly every single branch on this street tree was broken or bent downward, leaving only the very top branches. This wasn’t just a random “lets grab a branch and break as we walk by”, this was intentionally standing in front of a tree, breaking as many branches as you can reach. Cruel, senseless, disheartening, and more than a little bewildering. What can we do as  a community?

Just the other day a crew chief and I were interrupted by a student walking to class, and he’d mentioned how he had joined us tree planting on Arbor Day. He pointed to the tree he did, and said he can’t wait to bring his kids to see it in 30 years. So we keep planting, and keep pruning broken branches.

Leaf Color

Categories: Insects and Diseases, Trees

I’ve been reading quite a bit this fall in various newspapers, web sites, etc. about the science of leaf change, and I thought, well, heck, there goes another blog post. I don’t see the sense to retread ground others are covering.

By now, you’ve probably read that leaf color changes by the shortening of day-length light triggers the tree to begin shutting down the leaves, and that chlorophyll breaks down, and sugar is absorbing into the tree. In a nutshell, the veins connecting the leaf to the tree are closed (abscission layer), and once this is complete the leaf falls.

Weather does play a part in leaf color, and in the color you see in the hills as you visit your children on parent’s weekend here (Hi parents! Your kids are doing fine. They want more money.) Many articles have talked about warm weather delaying fall, cool nights are good, drought bad. It’s easy to understand, though, if you think of it in terms of plant health.

A happy, healthy tree in a good growing season will more than likely have pretty spectacular colors. The factors responsible for bad fall color aren’t good for the tree health either. Drought is bad for fall color, and also bad for the trees. Southern Vermont this year had a pretty bad late summer drought, and when I was on route 4 a week or so ago near Woodstock the leaves were terrible, turning brown and falling off, rather than turning nice colors. Here at Middlebury it’s been a dry September, and then the recent rain storms came at just the right time, and the leaves held on long enough to turn well. Warm fall days and cool nights? Good for sugar production, and the breaking down of chlorophyll in the active leaf. A late spring or a severe summer drought can delay fall color-the tree holding on to it’s leaves as long as possible, storing as much energy as it can before winter.

Another leaf color fact plant geeks have probably noticed is called the Leaf Wave Model. An article at the University of Georgia discusses this: Peak color is an opinion. Different trees turn at different times, and in differing colors. Yellows dominate early, then oranges as both later trees turn, as well as some yellow leaves becoming more orange. Finally reds dominate the landscape, with accompanying orange. Browns come last, generally in oaks. The leaves in Vermont are spectacular because of the forest cover types found here, yellow Ash, orange and red maples, along with splashes of green from Pine and Spruce. By paying careful attention to the mountains in the fall you can watch this leaf color wave happen.

Some other reading I’ve been doing this fall was about the color red, something I’ve never thought about. An interesting question for botanists has been “Why red?”.  As chlorophyll disappears from the leaf, the other colors emerge, such as yellows and oranges provided by Carotenoids. Red, though, is expressed through Anthocyanin, but is not found in a leaf, and must be produced. The question, therefore, becomes why would a plant be producing a compound, expending energy, at a time in it’s life cycle when it is trying to store and conserve? There are two schools of thought, and probably both are correct, some for some plants, some for others.

One theory is that anthocyanin is produced in trees in nitrogen poor soils. In some varieties of trees, as the green chlorophyll breaks down, the leaves are vulnerable to bright sunlight, and this sunlight breaks down the produced sugars, thereby not being absorbed back into the tree as energy storage. The red pigmentation acts like a barrier from the sunlight, allowing the tree to absorb more of the sugars it has produced. Nitrogen poor soils means the tree would have produced less sugars, being weaker growing, so more red pigmentation would conserve more of the valuable food.

The other theory is one of coevolution, that red leaves are a signal to insects as a repellent, a red warning signal to the insects attempting to use the tree as an overwintering site. A study has shown this in aphids and apple trees, that wild apple leaves turn red in the fall, and suffer less aphid predation.

Tree Planting 2010

Categories: Landscape, Trees

Of all the work we do here in the landscape department, some of the best is the tree planting.

Think of our landscape at Middlebury as a living organism, changing and evolving. Trees have a lifespan, like us, only measured not in decades but hopefully in centuries, for the best and strongest. Site vagaries not withstanding, most species live for a similar amount of time.  A mad rush of planting one year will mean that down the road a large hole may develop in the landscape, as the same aged trees all need replacing at the same time. Take, for instance, some work being done at Utah State University.

The main quad at Utah State is lined with 80 year old Norway maples, which in Utah live about 60-80 years. Plans are underway to replant the green, and to remove the Norways before they fail. This has met with some resistance, probably based more on disappointment, as the look of a beloved quad radically changes in the space of a couple short years.

We started our tree planting this year on Arbor Day, thanks to Hilary Platt and Chelsea Ward-Waller, two of my students from Winter Term, and the driving force behind getting Middlebury to become a Tree Campus. Many students helped plant trees around Bi-Hall, and near Coffrin. The focus for this area was to help define some of the space around Bi-Hall Park, as well as planting in between Coffrin and Bi-Hall to help with storm water abatement. We used Sweet Gum there, Nyssa sylvatica, and a variety of other native trees nearby, such as Hop Hornbeam, Scarlet Oak, Red Oak, and Ohio Buckeye.

Chelsea and Friends planting

More friends planting

The second focus of tree planting this year happened later, after the rush of commencement and reunion. I enjoy this so much so I almost don’t want to tell of it.

Part of a happy and sustainable campus landscape involves diversity. Having as many different species of trees as possible ensures that should the next insect (Asian Longhorn Beetle, Emerald Ash Borer) or disease come to campus, large sections of our tree population won’t get wiped out, like the aging Norway maples at Utah State.

So I prowl nurseries and garden centers, looking for healthy plants that will do well on our campus. With such a varied landscape, it isn’t difficult to find a spot to tuck in some type of tree somewhere. We focused this year on areas of the campus lacking in tree color, and used ornamental flowering varieties of trees to liven up otherwise very static green locations. An example of this is a small section of lawn right to the north of Painter Hall.

While not a large area, comparatively, it was large enough for three small flowering trees, set in a triangle. One was a Butterflies Magnolia, small yellow flowers in early spring. Later in June will come flowers from the Yellowwood nearby, followed by a small tree in bloom now, a Heptacodium, Seven Sons Flower. More on that species in a later post-it’s spectacular.

Other areas planted include North of Warner Science, where many over-mature Sugar maples are slowly showing the effects of time, as well as along the east side of Hepburn Road, and North of Gifford.

Hoopsii Blue Spruce north of Gifford

Paperbark Maple north of Gifford

Maackia amurensis north of Stewart

Other fun varieties planted were a “Discovery” hybird Elm, Red Obelisk Beech, “Katsura” Japanese Maple, Kousa Dogwood, and Yellow Birch (the kind they make Birch Beer from). 4 Different varieties of Magnolia were planted, one red, one pink, and two yellow. In all, 32 trees have been planted so far, and a couple more are still on the way. The Tree Karma count? Not exactly sure, with all the storm damage, but I’m thinking it’s still holding at 3.5 to 1 or so.

Big Huge Icky Giant Tar Spot

Categories: Insects and Diseases, Trees

Giant Tar Spot

The study of plant diseases made me terribly depressed in school, but also made me laugh on occasion. I imagined two plant pathologists walking around, looking at sick leaves. Of course, each of them wouldn’t admit to the other that they didn’t know or recognize some strange disease, so they’re making up names as they go along. Strange fungal spores on a cherry tree? Well, it looks like Black Knot, and the disease is named.

A fall arrival on campus (and occasionally in my inbox as a question) is always the blatetenly named Giant Tar Spot. (“Hey, what’s this?” “You don’t know that? Any idiot knows thats, um, Giant Tar Spot. Yeah, that’s it. Giant Tar Spot”) You guessed it, huge jet black spots on the leaves of primarily Norway Maple.  This, too, is a fungus, Rhytisma acerinum for you latinally inclined. It infected the leaves way back in early summer, but they don’t really show up until now. When it’s too late to treat.

Not that you need to. Late diseases and insects like this look terrible but, let’s face it, the leaves are only around for a couple of more weeks anyway. It’s not a bad year for it this year on campus, we’ve had it much worse. If you’re looking to get rid of it on your tree at home, rake and dispose of the trees at your neighbors…

The Plums are (nearly) ripe

Categories: Trees

I may be risking excommunication.

The landscape department, probably like many others across campus, has its share of secrets, little things nobody else knows about. My inside mole at the Grille keeps me updated when the linzertorte cookies are around. The view from the Bi-Hall roof after a snowstorm is spectacular. And, there’s a pretty spectacular plum tree on campus.

Plums are in the Rose family, the genus Prunus, which it shares with Cherries, Peaches, Apricots, and Almonds. The full latin name of the plum is Prunus domestica, The latin genus stolen from the greek word προῦνον (prounon), and the specicies domestica from the botanists term for “such a long and muddled history of hybridization we can’t possibly straighten it out”. It is no exaggeration to state that plums have been cultivated for thousands of years-Pliny the Elder writes of Apricots, stating them to be a type of plum, and a 6000 year old apricot pit was found in an archeological dig in Yerevan, the capital of Armenia. The earliest Prunus appear in the fossil record in the middle Eocene, about 45 million years ago.

Our plum is one of the first trees to bloom on campus, at about 80 degree days. In a good year, about 50% of the blossoms are pollinated, and bear fruit. Dry condidtions in the late spring will cause the fruit to drop while still small, and overly wet conditions are prime for Brown Mold, as unattractive as it sounds. Most plums are covered in a white waxy coating-this is a epicuticular wax that protects the fruit from UV light and also repels water.

There are many cultivars of plum. I’m betting, though, that our plum is a popular (and hardy, fortunately) variety known as Stanley. It’s a beautiful blue-purple color, with a golden meaty center, surrounded by a small pit. It was bred in the New York State Agricultural Experiment Station, part of Cornell University, located in Geneva. The station is  the mecca of hardy fruit hybridization, and brought us the Empire and Cortland apple. Stanley is literally the plum all others are now compared against. Richard Wellington developed the Stanley plum in 1926-when he started at the station, there was estimated to be 1 million plum trees in the state of New York.

Plums have a greater variety than other tree fruits, coming in many colors, sizes, sugar contents, and textures. They are an excellent source of anti-oxidants, more so than tomatoes, bannanas, apples and oranges. Marketeers are busy trying to sell us “dried plums”, hoping we forget grandmother’s name for them, the evil and dreaded prune. A sugar plum, aside from dancing in your head, is by law a plum with greater than 20% sugar content, at least according to the California Tree Fruit Agreement.

I enjoyed selling plum trees in my retail days. I was forever talking customers out of apples, as they aren’t really a tree as much as a pet, requiring greater care than anybody realizes. (Leave the apples to the experts-there is sanity in bulk) Plums, however, are carefree, without the serious pests and diseases of other tree fruits, and are self fertile, meaning one tree is all you need. Stanley should be hardy in most of the Champlain Valley, with perhaps the occasional late frost nipping the buds.

Oh yeah. I forgot to tell you where the tree is.

Lightning Strike

Categories: Trees, Weather

Our wild and crazy summer weather here at Middlebury continues, this time with a tree being struck by lightning. (Side note to the faithful readers out there. I feel for you-has this blog been getting depressing lately? With vandalism, more vandalismstorms, more storms, even still more storms, and disease,  it seems like the Middlebury Landscape is getting tragic. Hold the faith! We’ve been planting as well. Posts coming soon on this year’s tree plantings, as well as a new look for Pearson Hall.)

Ginkgo at 121 South Main

The tree hit is a Ginkgo ( read here if you’ve forgotten about them) located in front of one of Middlebury’s “outside” houses, near Public Safety at 121 South Main Street. I don’t know the night it got hit, but it was brought to my attention by one of the diligent members of our crew. Looking at the tree originally, I first thought the tree had just cracked down near the base, possibly in some strong wind. The tree shows what arborists call co-dominant trunks, where two trunks of equal size meet and grow together. This is frequently a recipe for disaster, as a bad union often results, where included bark makes a weak joint, and the two trunks typically fall apart away from each other.

Co-Dominant Trunks-click for a larger view to see the wound

I called an Arborist friend to consult on the damage-this is one of our favorite trees in Facilities, many of us would mourn the loss. His skill, knowledge, and experience led him to look up the tree, rather than me just jumping to the first obvious conclusion, and that was how he discovered the damage around the cable up top, as well as noticing the toothpick sized wood pieces scattered around the yard, small pieces of trunk blown away from the tree from the force of the lightning. Being tree geeks, we climbed up to investigate.

Damage around one the cables

Damage on another limb-the lightning jumped to this branch

Trees are frequent targets of lightning. Standing alone, frequently taller than many buildings around them, many trees get hit each year. Lightning is fascinating all on it’s own, with their impressive 100 million volts and  temperatures greater than 50,000 degrees fahrenheit. 16 million lightning storms are estimated worldwide in a year, and measuring instruments record over 100 million strikes in the U.S. each year, killing on average 90 people. They even get their own phobia, Astraphobia, fear of lightning.

The conditions needed for lightning are still debatable, but should those conditions exist, negative ions accumulate at the base of the storm clouds, while positive ions pile up on the ground. “Stepped Ladders” descend from the clouds, while “streamers” arise from the earth, typically strongest from the tallest structures, such as buildings or trees. Should they build strong and fast enough, they meet to form a lightning bolt, and this electrical discharge super heats the air around it to 36,000 degrees fahrenheit, compressing the air creating supersonic shock wave we hear as thunder.

When lightning strikes a tree, the sap in the tree boils, turning to steam and blasting the bark away from the trunk. The electrical charge flows through the tree, exiting out the root system, which could be severely damaged in the process, sometimes with no visible sign above. In most cases, though, a strip of bark is torn from the tree, often in a long strip, but sometimes, like this ginkgo, only above and below. Trees with only one crack tend to close the wound and suffer, yet live, while trees with wounds on both sides of the trunk are frequently killed outright. Obviously, even a wounded tree can die from secondary reasons, such as insects and diseases, less able to fight them off.

Trees vary in their susceptibility to lightning strikes, possibly for biological reasons, or possibly simply because of their height. Elms, Oaks, Black Locust and Ash tend to be very susceptible, while Beech, Horsechestnut, and Birch tend to not be very susceptible. It may be the starch content of the tree making it more susceptible, while resinous trees are poorer conductors.

So there is hope for our Ginkgo. The wound at the bottom was traced, where loose bark is peeled away carefully from the trunk to the point where it attaches again. The thinking with bark tracing is that loose bark can trap moisture and disease, so by removing it the wound can dry better. Maybe it’s just something to do to make arborists feel not quite so helpless…

Lower wound after tracing

Lower part of wound where lightning went to ground

The cabling up in the crown of the tree is a little more problematic. Originally put in place to help stabilize the two co-dominant stems, the system now obviously cannot be trusted, as the wood surrounding the bolts holding the cable is now dead. We decided to replace the cable with two others, one above the old cable (a better location from an engineering perspective), but also one looser below, in case one of the stems fails completely at the original cable site, and breaks. The tree will then still be braced by the lower cable.

Placing the cables in the tree

The three cables in place

So now, we wait. The rest of this year, and into next spring, will be the crucial time, and when we shall see just how bad the strike was. Should it still appear somewhat healthy next spring, we will aerate the soil around the tree, add compost, fertilize, and mulch. Hard to imagine now, but, if we get a little drought this summer, we’ll even go down to water.