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ImageLearn when to hire a pro for your home landscape at Scott McPhee’s Elm Bank workshop.  Photo courtesy of Bert_M_B via Flickr.

In the shrub pruning class I teach at the New England Wild Flower Society some student always asks me about pruning trees.  Unless we’re talking about nipping up the end of a low-hanging branch, or working on a small ornamental tree, for the safety of both tree and owner I usually recommend hiring a professional arborist to do the work.  For those who have questions about when to know what’s easily and safely done by Joe or Sally Homeowner, and what ought to be taken care of by an arborist, Scott McPhee of Hartney Greymont will give a talk this coming Thursday, July 11, called Trees In the Home Landscape.

Scott will discuss the tasks can be easily and safely accomplished by a homeowner, the tasks that really require a pro, and how to tell the difference.  An expert Hartney crew will demonstrate on a standing tree some of the principles that Scott is discussing, and then will demonstrate the tree’s removal.  It should be an excellent talk.

Location: Elm Bank, the headquarters of the Massachusetts Horticultural Society, in Wellesley, MA.

Date:  July 11, 2013

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It’s that time of year again!  This Friday is Arbor Day across America, and for Massachusetts arborists it’s the Arbor Day of Service.  Arbor Day of Service is a program developed by the Mass. Arborists Association several years ago.  For it, the MAA “partners with local tree wardens, community leaders, and civic organizations to identify worthy projects in need of professional tree care”.  Tree companies and individual arborists pick the project they want to participate in, and donate their time to plant, prune, and care for trees on the selected sites.  It’s a great program; various organizations which otherwise might not be able to carry out the needed work at one time benefit from the Arbor Day of Service blitz approach, and the arborists team with one another to give back to their communities.   Last year the arborists donated over $250,000 in services in that one day to the communities and organizations they chose.

To read more about Arbor Day itself, check out the Arbor Day Foundation website.  To find out more about the MAA’s Arbor Day of Service, take a look at the MAA website, which also has a signup sheet if you’re a member and haven’t yet put your name in to work on one of this year’s projects.

The two projects I’m most aware of this year are at Tower Hill Botanic Garden in Boylston, MA (worth visiting whether you’re there to do pruning or tree care or just to enjoy the site and gardens) and at Boston Common, one of the nation’s oldest common open spaces.

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I suspect this Boston Common pruning took place some time before the MAA started the Arbor Day of Service.   Still, it’s good to see the tradition circle back to the Common…

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.

 

Moving maturity

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.

Underground Peek

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

Elm root growth

Elm trees are known for their toughness in urban conditions; it’s why so many were planted in the American landscape.  For speed of growth, beauty of form, and wholehearted commitment to growing in all sorts of conditions, almost nothing beats Ulmus americana.  The elm’s Achille’s Heel, of course, is Dutch Elm Disease, which decimated the population of them through the twentieth century.  For the last half of the twentieth century, it was quite unusual to see American elms planted anywhere; they almost entirely disappeared from the market.

It wasn’t impossible to find them, though, and scientists and a few growers continued to work on developing disease-resistant strains of this majestic tree.  The Elm Research Institute grew and distributed clones of elms it believed showed resistance, and in the 1990s Dr. Denny Townsend, a geneticist with the National Arboretum, released two of the first DED-resistant cultivars of American elm, called ‘New Harmony’ and ‘Valley Forge’.  Bit by bit the American elm began to reappear in the landscape.

I was part of the design team for the streetscape restoration of Boston’s downtown area during the Big Dig design and construction phases.  We selected the National Arboretum elm cultivars, among a range of trees, to help fill out the planting palette for what became the Rose Kennedy Greenway.  So far, the trees have been doing swimmingly.

Last week Matt Foti’s crew spent a few days on the Greenway moving a collection of trees bare root from one of the parcels near Quincy Market.  The Rose Kennedy Greenway Conservancy will be building a permanent carousel on that parcel, and they wanted to save and reuse the trees that had been growing where the carousel will be placed.  Matt called to tell me about the work, which involved moving some red maples and some American elms that had been in the ground for the last 6-7 years.

The red maples, about 6″ in diameter, moved quite easily; their roots had readily broken out of the original root balls and grown nicely out into the planting medium.  Blowing them out was a simple process.

The American elms, however, had gargantuan root systems that seemed to go on forever.  Root growth was thick and profuse, and the crew had to keep blowing further and further out, and further and further under the root plate.  Here are photos that Matt sent of the elm roots:

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Tremendous root mass on an elm that had been planted only 6-7 years earlier.

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One elm getting lifted out of its planting hole.  Sinker roots had to be blown off; though the tunnel top is three feet below the surface, it appears that the roots on this tree had grown down to the concrete surface. Note the clean cuts on roots that had to be severed.

Hornbeam progress

Last spring I posted photos of a lovely little weeping hornbeam that the Foti crew had transplanted bare-root in downtown Boston a month earlier.  Matt Foti just sent me a couple of update photos, taken when his guys had been down on the Rose Kennedy Greenway to move a collection of trees from one of the park parcels near Quincy Market (a couple of photos from that project will show up in my next post).

The hornbeam thrived through the season, and is doing beautifully.  It had fully leafed out after planting, and the foliage looked awfully good.  Take a look:

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Nice dense foliage on the transplanted hornbeam.

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This tree apparently didn’t miss a beat when it was moved.