Trees are very intentional in their choices, by necessity. It’s a cruel world in the forest, and nature does not give a lot of second chances. Over millions of years trees and other woody plants have evolved very specific ways to grow, reproduce, and die, and much of this is predicated by growing together in communities in the forest
When a tree is growing by itself in a lawn and not in a forest setting, sometimes these mechanisms break down and don’t work. An example of this is the failure of one of my favorite trees on campus, a well known and well loved European Beech on the southwest corner of Battell Beach.
Many in our community will recognize this tree, I’ve seen people enjoying it for years. It’s a popular tree with slackliners, as well as hammock denizens. A low, broad spreading canopy gave a dense shade dappled with just enough sunlight to make it not quite feel cave-like. This beech, like some of the elms on campus, had a cathedral-like structure that made the tree feel like it’s own room, but this one was close enough to some major sidewalks that there was never a feeling of isolation.
One of the ways trees have evolved to live in a forest is to shed branches safely. Picture a forest community, with all it’s upper branches reaching for the light, growing every year skyward. Lower branches become shaded and unproductive, and these must be dropped rather than wasting upwards energy trying to sustain them. Trees have very specific branch attachments, so when a branch dies the tree can compartmentalize where the branch was, not allowing ddecay and fungus to spread into the main trunk.
In order for this to happen, the branch needs to be smaller than the piece it is attached upon. Sometimes, particularly in urban trees, the branches or trunks will be similar size, and this will cause a weak union, often made worse with included bark between the union.
The base of the Battell Beach Beech (couldn’t help myself there) was three trunks of similar size all attachted at the root flare, with an oddball trunk or two thrown in. All three had cankers at the base, and all had included bark in the union. Friday afternoon, on a calm day with zero wind or rain, one of these trunks had had enough, falling away, dropping nearly a third of the crown.
It’s possible this could have been prevented, at least in the short term. Other trees on campus have similarly weak attachments, and we’ve preserved these trees by careful pruning, or sometimes cables and brace rods. However, these beech not only had bad trunks, but large cankers (dead areas) were on all of the trunks, further compromising it’s health. Any interventions we could have done probably would have been for naught, or worst case made the tree worse.
With one of the trunks gone and the other trunk union between the two stems also weak, this tree is now much more structurally unstable than before the trunk fell away. We’ll be removing the rest of the tree before the start of the fall semester. While we sometimes don’t replant where trees have been removed, this is such a great location for a tree that’ll it’ll be high on the priority list.
Trees do everything relatively slowly-germinate, grow, live, even die slowly, sometimes taking decades. Arborists speak of a ‘mortality spiral’-when a tree suffers a series of compounding minor injustices and slowly declines until it’s eventual, and often undramatic, death. Owing to this tree time, in arboriculture there are very few red flag moments, those ‘drop everything and deal with this problem’ panics. Most of mine tend to be trees that have fallen across roads or fire lanes. Recently, we removed the Holiday lighted tree from the center of the main quad, having found a major red flag.
The Lighted tree was a Norway spruce, located next to Storrs Walk on the way up to the Chapel. There are only a couple of spruce left, but in past years they had formed a line on either side of the quad north of the McCullough Gymnasium, making a border and windbreak to what was athletic fields and are now our quad.
Film approximately 1930, thanks to Middlebury Special Collections- https://archive.org/details/middfilms_ff098 .
Norway spruce is a widely planted fast growing tree, native to northern and central Europe. They tend to live about 300-400 years in their native range and grow 60-80’ tall. The branches rise and ascend at the upper levels of the tree canopy, but gracefully swoop and hang down at lower levels. This is thought to aid in shedding snow in northern climes, but also lend a grace and beauty to the tree. Their fast growth and evergreen status make them a very popular landscape tree, and the wood is prized for its excellent tone in stringed instruments. We have many large specimens scattered on all corners of our campus.
This tree has had lights on it since forever. It’s a pretty good slug of work yearly to keep lit, as the squirrels on campus seem to love chewing the wires. One of our landscape workers was doing a safety check of the tree before replacing some of the lights when he noticed holes in the ground at the base of the tree. He called me over to inspect, and I ambled over.
We keep a close eye on all our trees, but some more than others. Probably 20-30 are on a list of ‘risk’ trees that we inspect yearly, most often older specimens in prominent locations. The lighted tree was not on this list. It has been in poor health for the last 15 years I’ve been here, in part due to location. Much of the root system near the base of the tree is covered in concrete sidewalk. Looking at the crown of the tree the poor growth rate was evident-little new shoot activity and a thin crown with few branches. But not all trees have to be perfect, just safe.
The holes around the root flare were indeed concerning, there were multiple locations where clearly a chipmunk or something had burrowed underneath the root flare. This was not the red flag, though. The excavation did not seem to be recent, and was not accompanied by mounds and mounds of dirt around the holes. I took a small tool and tapped on the trunk, usually my next step after inspecting the root flare.
As I suspected, it sounded hollow, a low thunky sound that’s hard to describe. Healthy wood has a solid ringing sound, like it’s proud of its strength, a low muted thump is usually the sign of rotten wood, a loud drum beat means it’s hollow. Taking a drill with a long but very narrow drill bit I probed several locations on the trunk. The drill enters live wood slow and needs quite a bit of pressure to do down into the trunk, but on soft, rotten wood encounters no resistance at all. I discovered about 1” of live wood before drilling through what was clearly rot. I drilled up about 5’ and found it was a column of decay from the base right up through the main part of the trunk. Probing and drilling around the root flare didn’t seem to indicate decay.
This is called a heart rot-the heartwood of the tree being attacked and decomposed by fungi, in this case probably Phellinus pini.Not the red flag though! Picture an old brick building, it’s interior walls long gone, but the solid outer walls holding strong for years. A tree can be hollow and still be strong, or at least strong enough to stay upright. Heart rot breaks down lignin, the structural cell component that makes wood strong and able to bear weight. Of more concern are usually sap rots, fungal species that break down cellulose in cell walls and compromises the flexibility of trees.
The red flag appeared as I walked up to the tree right at the very beginning, although I wasn’t sure. It seemed to me like the tree developed a lean, about 3 degrees towards the east, now appearing to loom subtlety but menacingly over the north/south sidewalk. I wasn’t sure, though. Looking at the ground next to the trunk it appeared slightly heaved up on the west side, but not dramatically so.
A persistent tree myth concerns roots. Roots don’t go deep, certainly not as deep as the tree is tall, and very rarely do trees have a true taproot. Instead, most tree roots are found within the top foot of soil, extending out past the crown of the tree. Most trees will send sinker roots down from those lateral roots, driving about 2-3 feet down, like a tent stake. Norway spruce, however, don’t grow a lot of sinker roots, and as a species tend to be prone to tipping over, particularly in clay soils or high wind locations.
We have both here, high winds from the west coming downslope, and a heavy clay soil prone to seasonal moisture at the base of the ledge. Remember the soil was heaved on the west, and we also noticed a crack in the trunk. Clearly, something was moving around here. The technical, and scary sounding name is Root Plate Failure, and it’s a big deal. Trees can be hard to define, but I prefer the concept of them being a large woody plant that if it falls on you will kill you. Root plate failure means the tree has lost its support and can fall. Seeing ground heaved up next to the trunk means recent and dramatic failure, and for organisms that do everything slowly root plate failure is lightning speed in tree time.
Trees need three items to be considered a risk tree, here we have all three. One, a part that could fail (the roots), second, a mechanism for failure (wind, upcoming winter snow load), and three, most importantly, a target. The sidewalks, the fire pits, tent out in the quad, all this means many people walking around, a classic ‘target rich environment’.
It is, however, the lighted tree. All trees deserve thoughtful consideration before removal, but iconic trees in prominent locations up the ante. Giving it every chance we could, we did an old fashioned pull test. Sounds fancier than it is-tie a rope most the way up the tree on the trunk, stand way back, and have a couple people pull, simulating a windstorm. A couple people pulled towards Old Chapel, and I stood at the base of the tree and felt the trunk and ground. Sure enough, the ground beneath me moved, and the entire trunk flexed all the way to the base. This was enough of a red flag I started calling every manager/director/vice president I could reach while we had the rope in the tree, as this was best experienced live.
The International Society of Arboriculture certifies arborists in Tree Risk Assessment, and I usually run through the process before any removals. I feel like we owe it to the tree. Following standard Tree Risk Assessment protocols, with high consequences of failure and a somewhat likelihood of failure and impact I determined this tree presented moderate to high risk.
Mitigation options other than removal are non-existent. Tree based interventions, such as preventing wind throw by bracing or crown thinning are contraindicated in both the species and this tree, and there are no treatments for heart rot with such advanced decay. Given the high activity near the tree with the tent, fire pits, et.al, site-based interventions such as moving pedestrians or restricting access is not possible. Sadly, given the level of risk remaining, we felt like the tree should be removed. We waited until holiday break, to not make a lot of noise during final exams.
It’s not your imagination, the leaves are turning early this year. The reason will seem a little odd, but an understanding of a tree’s relation to time helps.
I feel for scientists that have trouble explaining the concept of time. We are lineal creatures, stuck watching time pass from one year to the next. As a horticulturist, my year goes from spring to spring. But anthropologists measure civilizations in centuries, not our ordinary years. How about geologists, counting back years by the billions. Most impressive, let’s talk about Astronomy. A light year-the time and distance it takes for a photon of light to travel. It’s called the speed of light for a reason.
Tree time moves differently. Trees do everything slowly-germinate, grow, mature, reproduce, even die. Some varieties live well within one of our short lifetimes, while others will live for generations. Time moves in fits and starts for a tree, on yearly cycles familiar to those in Agriculture. But they aren’t exactly lineal.
Remember last year? It was a growing season in a bitter drought, with no rain for most of the spring, all of summer, not breaking until late in the fall. It was hot, dry, and overall not very pleasant. I use our annual flowers we plant as a barometer, and the ones we planted around campus languished in the heat, and with the exception of some petunias none ever really amounted to much.
Our tree canopy looked OK though, and we had a nice fall. But this year, not so much. Maples are turning early, losing their already smaller than normal leaves about 4 weeks too soon. Oaks have been thin all year, with many dead twigs and branches. But it was a great growing season this year, with all flowers blooming non-stop since commencement. But not in tree time.
Trees are about a year off, marking time in their own way. They leaf out and grow all season, but reach back to the previous year’s sugars and energy stored from the prior growing season. Last year’s food is this years energy. So the drought last year certainly affected the growth of trees, but on tree time it doesn’t show up until this year. Weakened roots and inadequate resources in twigs and stems are stunting growth this year, and trees are wearing out and starting to turn early. Trees live a dual year, growing in the previous year while stockpiling for the next.
Ordinarily in the early fall there are always a couple of trees starting to turn, and the easy answer is that they are weakened, stressed trees, our canary in the coal mine showing us underlying problems we might not have seen. Usually the Black maples east of Old Chapel turn fall color early, a problem of not only age but poor soil and compaction from living in a college quad for 200 years. This year, though, it is many, many trees. Primarily sugar maples, and mostly middle-aged trees, I’d guess 40-75 years old. In tree time for a maple you can think of them as 30-year olds facing a mid-life crisis with all the associated baggage. Primarily we’ve seen trees turning this year as ones in poor soil, either on ledge, or heavy clay. Above my house on Snake Mountain I see the canopy turning color, the relatively young forest showing it’s stress.
Younger, less mature trees are probably more in balance, and also flaunt vigorous and resilient root systems, while old, mature veterans had the massive underground roots to weather the (lack of) storms. Neither are showing the stress or are turning early.
It’s too soon to say what the fall will bring for color, but I’d sure like to see a little more rain soon, and a break in this mini heat spell we’re having. I do predict an early season, though, maybe longer if the oaks in the lower elevations can hang in there.
I’m not much of a writer, so I won’t bury the lede here-our annual Arbor Day celebration will be happening tomorrow, October 7, starting at 4:00. I’ll be giving one of my walking tree tours through campus, followed by a tree and rain garden planting about 5:30 or so. Cider and donuts provided. Here’s the events listing for a sneak preview-
Meet on the front porch of the Franklin Environmental Center (FEC) for the very popular Campus Tree Tour led by passionate Middlebury horticulturalist and tree expert Tim Parsons. This year, FEC is focusing on the theme Urban Innovations, Sustainable Solutions, which will include exploring connections between urban and rural. As part of the tour, Tim will explain why he manages our rural Vermont campus as an urban forest. Stick around after the tour for a tree planting, complete with hot cider and fresh local donuts. Bring your willingness to learn about and to get a little dirty.
And this is a sneak preview-
Anyway, where have I been and what am I thinking?
Anyone blogging in an academic setting probably knows the difficulty. I liken it to a lead weight between my shoulders. I know I should be posting more, but being surrounded in an environment filled with people much smarter than I means a blog post needs to be weighty, relevant, and not a stream of consciousness this is turning into. In short, a blog post is something that takes considerable inertia to start.
But start I shall. And, naturally, I’m starting with the landscape. Come on my tree walk, I’m picturing it as an “Envisioning Middlebury-Landscape Edition”, to piggyback off the excellent work the community conversations around this topic that are happening. Un-facilitated though, unless you count the trees. (I’ll show you how they are talking back to us.) Landscape is not static, and as we discuss the future of Middlebury let’s not forget the outdoor physical environment as well.
Abnormal weather always has people worrying about their trees and shrubs in the yard, and this winter is anything but normal. It’s the warm temperatures that are troubling, and many people have come up to me asking if the trees are going to be OK, or if the warm temperatures mean they are going to start growing.
Surprisingly, it’s the opposite, but this winter is a long ways from being worrying.
All temperate climate plants go through a period called dormancy, a mandated winter rest. This is triggered in the fall by not only temperatures, but by day-length. As the days get shorter the plants go through chemical and physiological changes to prepare for below normal temperatures. Once dormant, the plant needs sustained cold (500-2000 hours below about 40 degrees) to break dormancy and get ready to grow again in the spring. So, if this winter were to have stayed above about 50 all winter long the plants wouldn’t have started to grow, but the opposite, would just sitting there doing nothing.
And this makes sense. I’m always amazed at how smart and resilient plants are. While this winter is fairly unusual in the sustained warmth, we do see warm spells most winters, and plants that would start to grow at the first blush of spring wouldn’t be around very long. Breaking dormancy requires not only warm temperatures, but increasing day-lengths, longer spells of sunshine to break their winter gloom.
What can hurt a plant is freezing temperatures once dormancy is overcome. In trees, this is seen as frost cracking, long vertical fissures in the bark caused by water freezing in the xylem after warming up and moving around in the daytime. (Look at the trunk of the Sycamore in the triangle in Wilson Terrace outside McCullough)
This adaption to day-length also explains why plants with a local background (called provenance) is best. Day-length varies by latitude, with greater variation seen in northern latitudes. Take a tree from Vermont, move it down to Georgia (poor thing), and it will stop growing mid summer, as the days are a northern fall-like short. What I see quite a bit more, though, is the opposite. Plants grown in a nursery down south and moved up north don’t know when to shut down and start dormancy, and are often growing late into the fall, with their leaves and twigs freezing, unprepared for winter.
And while I’ve got your attention, let me take care of one final question I’ve been getting. No, your lilacs aren’t ‘budding’. Many people are looking at their giant buds on the ends of the lilac twigs, and think they are swelling about ready to pop and start growing. They were actually that large this fall, you just were too busy looking at fall foliage. Fear not.
Middlebury is ending the semester awash not only with hard discussions on stress and appropriation, but with a new surge of tree vandalism.
Four trees have been vandalized in the last four days. Three this past weekend, 1 pulled up out of the ground by Battell, one by HMKL pulled up and dragged to the front door, and one snapped at the base, only 20’ from a dorm.
Then two nights ago a memorial tree was rocked back and forth, unsuccessfully broken off, so instead all the branches were snapped off, and the top severed and left on the lawn. This is a new on our campus, as we’ve never had a memorial tree killed before.
Don’t think of it as vandalism, however, think of what is happening as aggression and violence. Vandalism is breaking off random branches here and there; violence is taking a well-established tree with a 3” trunk at rocking it back and forth for probably ten minutes until it snaps and breaks at the base. A former student wrote an entire term paper on tree vandalism, and told of the link of alcohol fueled aggression and violence against trees.
But, like many problems here on campus, who dares speak up? I’d certainly be nervous to confront someone in the act, and I carry chainsaws around for a living. I think back to my time on community council last year, with long discussions led by Ben Bogin on a Social Honor Code, not just an academic one. Read William and Mary’s code, or Haverford’s, with their ‘Confrontation’ philosophy, as difficult and engaging as President Patton’s wish for more and better arguments.
So maybe our department no longer plants smaller trees, as the smaller size seems to encourage vandalism. The field house, for example, was planted in 3” trees, and they would be nearly impossible to pull out of the ground. The problem with that, like many problems we face this semester, is the concept of resiliency.
Like people, trees and forests do better in large, diverse groups. Diversity brings resiliency- look to the lessons of Dutch elm disease when many, many towns lost nearly all of their shade, or look to our future when Emerald Ash Borer moves into Vermont and destroys all our ash trees, almost 15% of all trees on campus. We are diverse in tree species, so 15% is a hit, albeit an unpleasant hit that we can suffer through.
But only if we keep planting our forest without ceasing, and keep the goal of diversity. The nursery industry in Vermont doesn’t have a big diverse selection in large trees, so we plant smaller unusual trees in addition to the larger ones. Smaller trees are also easier to plant, and cheaper, so we can plant more trees in a year, and come in many different species, much more than basic maple, oak, and honeylocust. It’s these small trees, however, that keep getting vandalized, snapped, and pulled up out of the ground.
Our campus forest is losing resiliency, and to be honest, so am I.
I’m hosting a tree tour and tree planting for our fall Arbor Day celebration this Wednesday at 4:30. It’s part of the 50 Years of Environmental Education & Leadership at Middlebury celebration (view the whole schedule here). We’ll be leaving from the front porch of Franklin Environmental Center (Hillcrest), wandering around wherever my feet and your questions take me, and ending up back at Hillcrest about 5:30 to plant 3 oak trees on the corner.
The oaks are coming from Miller Hill Farm in Sudbury, and are a mix of Red and Bur Oak. We’re replacing two blue spruce that died in that location, and these will be hardy long lived street trees. Another Sugar maple is dying nearby (not a great street tree, by the way), so the oaks are particularly fortuitous here.
And of course, doughnuts and hot cider. Come be as happy as these volunteers last year!
The drought continues here on campus, and in the broader Champlain Valley. Our last rainfall was .4″, and after transplanting a tree afterword I saw the ground had only gotten moist about 1″ down-powder dry soil beneath.
I forget where I found them (probably Lifehacker), but some recent pictures of the US taken by the Gravity Recovery and Climate Experiment satellites show in stark maps the bubble of drought we seem to find ourselves in right now. The first map shows soil surface moisture, moisture in the first centimeter of soil. Look for the little dark red blob right on top of Middlebury. (click on maps for larger view)
The next shows root zone soil moisture, the top meter (39″) of soil.
This final map shows ground water in shallow aquifers (like the well at my house!).
I’ll include the overall map of all three maps, which give a legend to the colors. The explanation is as follows (and is quite scary!)-“The maps do not show an absolute measure of wetness, or water content. Instead they show how water content in mid-September 2015 compares to the average for the same time of year between 1948 and 2012. Dark red represents areas where dry conditions have reached levels that historically occur less than 2 percent of the time (once every 50 or more years).” Note how we are in the dark red in all three maps.
If you have a little bit of time, by all means read how gravity sensing satellites can figure out how much water is in the earth. In a nutshell, it’s two satellites seperated by 139 miles, and sensing how much they move towards or away from each other as they orbit minute changes in gravity from earth can be measured. The complete explaination is at http://earthobservatory.nasa.gov/Features/GRACE/ .
Hope is on the way, though. We’re looking at a pattern change, with a cold front moving into the area and drawing moisture into the region, possibly an inch of rain or more. That’s a good start. Here’s a good rundown from the Northeast River Forecast Center.
Our barely green lawns across campus belie a hard fact this summer-it’s been dry. Very, very dry.
Funny, considering how wet it was in late spring, when it was almost too wet to do anything outside. The High Plains Regional Climate Center (kick ass website for weather geeks!) maps show we have 25% of the normal precipitation in the last two months, that’s a 6″ deficit of rainfall.
A general rule of thumb I can’t find a reference for but I always tell anyone is that Vermont plants need a 1/2″ of rainfall per week for optimum growth. We’ve had only about 1″ in all of August, and only 1″ in July. Most of that falling in one day, leaving our clay soils to dry out and become nearly resistant to small rainfalls.
The early leaves you see falling are signs of that. Trees in temperature zones such as ours develop wide, spreading root systems, not going too deep in search of water or nutrients. In fact, much of our campus is on ledge, with very little topsoil available, meaning plants need to go shallow and wide to root into the ground.
(My unsubstantiated theory is that Middlebury was founded where it is because of the ledge-poor soils make poor farmland, and why waste valuable agricultural soils and farmland on something as unimportant as a college? Farmland in 1825 was precious, hard earned space, so let the geeks have the hill, we’ve got crops to harvest)
These wide spreading root systems enable fast, efficient uptake of water and nutrients in poor soils and a short growing season. In ordinary years, this is ideal, but in dry years, this strategy can be costly. As you can imagine, the shallow soils dry quickly, and the plants don’t have the deep extensive root systems to find moisture in the lower soil profiles. Trees are gamblers, and they’ve got a losing hand this year.
Flowers and other perennials show stress by wilting-the curling of the leaves cut down on the loss of water through the stomata (transpiration, if you want to flash back to high school biology). Trees react like that too, but also have the ability to shed leaves. We are seeing this now, and it may cause an early fall. The inner leaves on trees turn color and fall away, a survival mechanism. Inner leaves in the crown are not as efficient, they don’t photosynthesize as well, and therefore are not as “useful” to the tree as the outer, younger leaves. In desperation, the tree will shed the inefficient leaves ,brutally choosing the younger leaves to use the precious remaining water they have remaining.
We’ve had a little bit of rain this weekend, and more is coming, so luck it will come in time to prevent a wholesale dropping of leaves before your parents come up for fall family weekend. Snake Mountain above my house is starting to turn brown along the ledges, though, though, so lower expectations while you can.
I love getting emails from people concerning the landscape. After all, with more than 300 acres, there are probably things happening I’m missing. And in the chaos that is Commencement and Reunion, I was missing a big one.
Professor Jeff Byers wrote last weekend-
I don’t know if there is anything you can (or would) do anything about, but there is an oak tree between BiHall and Coffrin that was in the process of being totally devoured by gypsy moth caterpillars! There were so many that I could hear the hum of their munching under that particular tree.
I went right over. (the joys and perils of instant email on my phone-it was a Sunday.) I was terrified it was the giant Pin oak tree, the one that made the list of the twelve oldest trees on campus. Fortunately, it was one of the Poplars nearby. And was I impressed.
I couldn’t hear the munching, I think they were all fat and lazy by the time I got there. Much like me on a sunday. Not Jeff-have you read his blog? The last time I did a trail run up the wrong secret side of Snake Mountain I came down with Strep. I reached up to one of the many defoliated leaves, and grabbed a caterpillar.
Jeromy Gardner, our elm guru from Bartlett Tree in Manchester, correctly identified it as Satin Moth. Not worrying, but has a habit of building a large population every so often and completly covering a tree, in this case our White Poplar. Here’s a great article, if you are interested. They were originally thought to only attack exotic poplars, such as Lombardy poplar and European White poplar (what ours is), but now also is seen in forest stands, and could become significant if defoliation occurs for several years in a row. It does, however, have plenty of natural enemies, including parasitic insects, bacteria, fungi, even birds.
So all that remains on the tree are the major veins of all the leaves, everything in between them eaten. I fully expect the tree to re-leaf in a couple of weeks or so. What is even more interesting is the other white poplar about 30′ away, with only a minimal population. The infested one was in a construction zone a couple of years ago. Maybe the stress of root compaction has something to do with this? Or I’ll be writing about both trees being infested next year…
Thanks to Jeff for pointing it out. Maybe I’ll host a ‘trailrun’ of the trees on campus someday this summer. Better start training now.