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Archive for the ‘Trees’ Category

A few weeks ago I was on Beacon Hill to run an errand, and snapped a quick shot of the Shaw Memorial elms in the rain:

RS cropped Shaw Elms

Looking across Beacon Street to the Shaw Memorial; the two elms flanking the memorial are being managed to retain their trunks’ stability.

It was a soggy, cold day, and I was fast getting soaked, so I didn’t cast around for a better shot.  These elms have been standing on Boston Common, across from the Massachusetts State House, for centuries now.  This State House (for a long time known as the “New State House”, so as not to confuse it with the original State House on Court Street) was built between 1795 and 1798; the elms date at least to that time, if not to a couple of decades before then.

Elms are a fast growing tree, and before the onslaught of elm bark beetles that brought Dutch elm disease to these parts, Boston Common had a thriving population of elms.  (For a good look at the role of the American Elm in history since colonial times, see Tom Campanella’s fine book, Republic of Shade.)  The elm stand has been so reduced that now only a few specimens remain; I remember in the summer of 1997 or ’98 watching as a row of elms below the Common cemetery was taken down, tree by tree, as the disease raced from one end of the row to the other.

Henry Davis, owner emeritus of Lowden Tree (now part of SavATree), was landscape consultant to the Friends of the Public Garden for over forty years, and he was responsible for developing the treatment regimen that aimed to save elms as long as possible.  Using a combination of pruning and tree injections, he was able to preserve quite a few elms for quite a long time, including these Shaw Memorial trees.

The trees are rooted in the sloping ground now covered by Augustus St. Gaudens’s Robert Gould Shaw Memorial and Massachusetts 54th Regiment Memorial, which commemorates the first documented black regiment formed in the north during the Civil War.  The memorial, which includes a two-story retaining wall and St. Gaudens’s relief sculpture, is itself flanked by two broad granite stairways.  The elms rise out of a vault under the memorial; maintenance on the lower trunk and roots is performed from inside the vault.

These elms are actually rooted several feet below the memorial's floor grade, in a vault built into the Common's slope.

These elms are actually rooted several feet below the memorial’s floor grade, in a vault built into the Common’s slope.

If you saw the last post in this blog, you may understand the thinking behind maintaining the Shaw Memorial elms in this way.  These two trees are two of the oldest trees on the Common, and stand as witnesses to American Constitutional history.

A few days after I took the first photo, I spoke to Norm Helie, who now guides the Common’s tree maintenance.  Norm told me that he had just had further top weight taken out of the Shaw elms, and the pruning cuts had removed tissue down to sound wood.  I made my way down to the Common, and took some more photos — on this day, a demonstration in front of the State House prevented me from repeating the rainy day shot angle, but I was able to get a photo of the new cuts and the State House, to boot:

Here's what the elms look like with still more weight taken out of their tops.  Retrenchment pruning of veteran trees is radically different from structural or maintenance pruning of younger trees.

Here’s what the elms look like with still more weight taken out of their tops. Retrenchment pruning of veteran trees is radically different from structural or maintenance pruning of younger trees.

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Last week I drove past the Paulownias I wrote about in 2009, and realized that they deserved another blog post.  In the four years since that post, all three trees have shot up.  

I kept trying to shoot an image with the two paired trees in it, minus the utility lines, but it wasn’t doable without risking life and limb.  The trees have grown higher than the house and the utility lines, and have easily tripled (at least) in size.

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Two paulownias planted four years ago now shade almost the entire front yard.

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The smaller of the two trees measures perhaps 12″ DBH.  The once-sunny walkway is now almost entirely shaded.

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It’s a little tricky to see, but the right-hand tree is larger than the one to the left.  Directly behind it stands a large Japanese maple; in the 2009 post you can see the maple’s fall color, and compare its trunk size to the now-towering Paulownia’s. 

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Air-tool transplanting is continuing here in Massachusetts; while it hasn’t yet become commonplace, arborists in this part of the world are conversant with the techniques, and some firms have been routinely been moving trees bare-root for the last few years.  Leahy Landscaping of Lynn, MA, has a team of transplanters, led by Mass. Certified Arborist Bob Dobias.  Bob recently sent me some photos of a project his crew carried out this past summer; they moved a beautiful 14′ Fastigiate Beech in Salem with air.  They relocated the tree from a location right next to a building to a spot further out on the property, where it can now grow to its full potential.  Here are the pix Bob sent:

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This tree has been growing nicely next to a condo entry, but was likely planted there when it was a much smaller specimen.

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Bob has exposed the topmost roots, and is working his way underneath the root mass.  Note that he’s wearing ear protection and has dust barriers set up around the work area.

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Fastigiate Beech is a narrow tree, and while a blowout to the dripline frees most of the roots, some root mass still had to be cut.  Bob reports that his crew cut one root that was growing under the driveway.

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Nice root mass on this tree.  The time had arrived for this tree to be transplanted; notice that the roots to the right are shorter and have been redirected down by the presence of the building wall.  A tree that grows for too long this close to a wall might not be as readily moved as this one — not because it can’t be dug out, but because the root mass has grown too asymmetrically for the tree to stand well away from the wall.

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The Beech being introduced to its new home.  According to Bob, the crew could have lifted the tree by hand, but decided to use the machine to minimize hazards to it.  For the actual move, they tied the tree to the forks; this shot, it has been untied and is being guided into the planting hole.

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And from a different angle.  The hole receiving it could be a bit wider, to make the backfilling and mudding in easier, especially as there are no obstructions around it.

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With the tree placed in its new home and backfilled, the crew waters and muds it in.  Leahy added better loam for backfill, and secured the tree with duckbills, to insure stability while it grows into the new location.

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Proud Leahy crew and Fastigiate Beech.  The Beech should now be able to grow a little fuller both above and below ground on the side that had faced the building.  The transplant operation took about six hours from start to finish.

Bob reports that the tree has experienced some stress from the move, but he expects it will equilibrate crown and root growth and leaf out well next year.  We’ll keep an eye out for more pix next year, to check its progress.

Fastigiate Beech moved by:

Leahy Landscaping, Lynn, MA

Arborist in charge:  Bob Dobias, MCA

Crew:  Alfredo Esteban, Shane Corcoran, Greg Beatrice

 

 

 

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Last February I wrote about the bare-root transplant of a large Katsura tree (Cercidophyllum japonicum) at UMass, beautifully executed by the pros at Foti Landscape and Tree. Matt Foti just sent me a photo he took last week of the tree, which has settled into its new home nicely.

Though the crew kept a large slug of soil under the tree’s butt for the move, Matt told me that they did some excavation at the root flare, as they always do, to check for girdling, circling, or damaged roots. (I hadn’t noticed the excavation when I first saw the transplant photos, but if you click back to that post you’ll notice it.) The crew found a girdling root and removed it — and clearly, from this current photo, the tree didn’t skip a beat.

Even in a backlit shot on a very hot day this tree is looking happy.

Even in a backlit shot on a very hot day this tree is looking happy.

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This year’s New England Grows featured a talk by Jim Flott, who discussed the bare-root transplanting of large trees.  Jim talked about root-washing, something he has studied, practiced, and taught, on his own and with the late Bonnie Appleton of Virginia Tech.  He spoke about the history of bare-root transplanting — until the middle of the 1900s bare-rooting was the primary way to transplant trees — and about bare-rooting with air tools.  It was a great presentation; this abstract by Flott and Appleton covers a lot of the territory Jim discussed, and it’s worth a read.

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Bare-root transplant with air tools — 12″ caliper London Plane tree, moved in late July 2009 in Wellesley, MA.

After Jim’s talk in one of the large auditoriums, he moved to a smaller room for an ‘Speaker Unplugged’ session, where people could ask him questions and exchange information.   As had happened at New England Grows three years ago, when Matt Foti discussed bare-root transplanting with air tools, someone asked about the effects of bare-root transplanting on a tree’s taproot.

How does bare-root transplant affect a taprooted tree?  The answer, both from Jim and from Matt, is that taproots are rarely an issue.

A taproot typically forms when a seed germinates; the baby taproot emerges first from the seed, growing down and anchoring the seed in the soil.  Next, the cotyledon shoot emerges and grows upward.  As the cotyledon starts to photosynthesize, root hairs branch out from the taproot, and the root volume grows and spreads.  The depth of roots is determined in part by available moisture and in part by soil type.  Typically, organic soils — which hold water and allow good cation exchange — rest at the top of the soil profile; mineral soils underlie the organic horizons, and are much less hospitable to roots.  Here in New England soils may be quite thin, and are often underlain with rock.

So taproots here will serve that useful anchoring function early in a tree’s life, but soil conditions and the plant’s own tendencies will promote the outward, rather than the downward growth of a tree.  In fact, the overall growth of tree roots tends to be outward, rather than down; the old image of a root mass volume and form mirroring a tree’s crown volume and form has been proven false.

We know that trees tend to develop their roots in the top 18″ of soil; the larger the tree, the deeper that zone may go, but typically it extends no more than 3 or 4 feet below grade.  Some thick roots on very large trees may extend vertically down in this zone, if soil conditions permit, but many more run horizontally away from the tree’s trunk.  The anchoring function of that original taproot, if it remains, is replaced by the anchoring provided by a much broader and more extensive mass of roots growing out and (to a much less extent) down.

As I wrote in an earlier post (with thanks to Linda Chalker-Scott for its title):

It’s helpful to keep in mind another factor when thinking about taproots and transplanting trees.  More often than not, a large tree being transplanted was planted out years earlier as a B&B plant, or possibly moved into place with a tree spade.  Both methods would have cut any taproot in the initial planting.  When the end of a root is cut, the tree tends to send shoots out from just above the cut end.  In a vertically oriented root, the new shoots are apt to extend horizontally from the cut end, and feeder roots would similarly extend out horizontally.  The situation may well be different for a tree that has grown from seed in one place, that someone now wants to transplant bare root, but for most landscape trees the taproot issue is moot — whatever taproot may have existed when the tree seed germinated has already been cut, and the tree has adjusted for its loss.


A carrot grows downward, with rootlets out to the side and foliage above ground. A tree is not a carrot. Photo by obenson in Flickr.

This beech tree was moved last fall, having been transplanted once about 20 years ago. See how the root mass extends far out horizontally, with a relatively shallow depth.

This is one of the thickest roots extending vertically from the beech’s trunk. This root was cut in the earlier (20 years previous) transplant; note the resultant root growth just above the cut.

 

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Last fall Matt Foti‘s excellent crew moved a mature Katsura tree (Cercidiphyllum japonicum) on the UMass campus in Amherst.  Jim Flott showed one photo of the tree in his New England Grows presentation last week, to illustrate the breadth of a root mass; take a look here to see what it looked like during and after the soil blowoff.

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Notice the trench dug around the entire root mass.  Typically, the crew uses a line tied to the trunk to swing and mark the edge of trench at the tree’s dripline.  If really significant roots appear once the first buckets of soil have been dug, the crew can decide to shift the trench edge outward to save more roots in the blowoff.  Alternatively, if no roots are found that far out from the trunk, the excavator can dig closer in to the trunk until roots appear, and the trench placed at that diameter out from the trunk.

Plywood is visible to the left of the photo; soil is blown into the trench for removal, but plenty of soil and dust fly around, and the plywood barriers help contain it, and keep the surrounding site cleaner.  The soil pile behind the plywood is what has been excavated to form the trench.

According to Matt, this tree is 20″ dbh, with a 22-24′ wide root mass.  The crew blew it off in one day, and moved it about 2,000′ away the next day.

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One of the benefits of air tool work like this is the fact that roots become visible, and it becomes clear how a tree grows below the soil surface.  The roots here obviously cover a huge area, and their density and branching suggest resilience and vitality.

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Notice how much soil remains around the base of the tree.  Leaving a slug of soil makes it easier to place the tree level in its new location, at the correct depth.  The crew usually blows soil first from the root tips, and works back toward the trunk, always blowing soil toward the trench.  The circular track around the tree’s trunk was made by the crew toward the end of the blowout, as they worked their way around the tree.  Pigtails of roots are held off the ground with lines tied back to tree branches well-padded with burlap.

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Katsura en route to its new home on the UMass campus.  Interesting to note how dense and finely branched the tree’s crown is, especially in light of how dense and finely branched the root system is.

Stay tuned for more photos of this tree in the next few months, when we get some followup shots after it has leafed out.

Location:  University of Massachusetts, Amherst, MA

Moved by:  Matthew R. Foti Landscape & Tree Service, Inc.

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It was just over a year ago that an ecologist and ISA-Certified Arborist, Lisa Montana, contacted me from AECOM, the global architectural/engineering giant.  She works in New York City, and is involved on projects that require utility trenching under sidewalks and around the roots of adjacent street trees.  When her project sites have contaminated soils, excavation must take place with shovels and bars, the old approach to bare-rooting plants.  On sites with clean soils, the workers use air tools, which let them remove soil and preserve important tree roots.

Lisa kindly sent me some photos of air-tool trenching projects she has overseen, and with my apologies to her for the long delay, I’m posting them here.  Take a look, and note how persistent and vigorous those critical roots are even underneath concrete pavement.

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This one is a 26″ dbh Honey Locust.

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This astonishing root mass belongs to a 28″ dbh Oak.

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These roots come from an enthusiastic 29″ dbh Norway Maple that needs the rooting area in the lawn beyond the sidewalk.

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This final photo shows a 32″ dbh London Plane whose roots are seeking moisture in the bed beyond the fence.

It appears as if each of these trees is reaching underground toward open ground, where adequate moisture and air can be found to sustain them.  I have been mulling over these photos for some time, and especially since Hurricane Sandy, when so many uprooted New York street trees appeared to have root masses that conformed to the bar-like shape of their planting spaces.  I wonder if those root masses had been cut at some point, as is often done for the reconstruction of a sidewalk or for utility work done in a less sensitive way than AECOMM’s methods.

Thanks, Lisa, for sharing these photos, and giving us a peek at what’s going on under some sidewalks.

Location:  New York City

Arborist In Charge:  Lisa Montana, AECOMM

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