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A reader, Mark Vanderwouw from Shady Lane Expert Tree Care, Inc. wrote a comment on the post titled Another Air-Tool Bare-Root Transplanting (cross-posted from TakingPlace.net, the other blog I co-write for landscape architects).  His company is excavating out several large specimen trees for a one-year storage period, after which they will plant the trees in their new home.  I answered his questions in the Comments section of that post (click on the link above and scroll down to the Comments), but they, and the questions I’ve been asked quite a bit in the last few months, need airing and discussion in a larger format.  So here goes:

Q:  How long did it take to excavate the Taxus and the Kousa Dogwood that were  growing next to each other?

A:  It took the better part of a day to excavate and transplant these trees.  Because their roots were intertwined, the process took longer than it would have had they been stand-alone specimens.

Interwoven roots of two trees to be moved makes the excavating process more time-consuming.

Q:  Is it necessary to keep the roots moist during the excavation?

A:  It is a good idea to do so, as compressed air tends to dry soil and roots.  Having a hose on hand to spray down the exposed roots every so often makes sense.  There has been some discussion among the arborists doing this work that because such a large volume of root mass gets saved, the tree is much more resilient and adaptable to the short period of drying caused during air-tool work.  Compressed air will blow off quite a lot of the tiny feeder roots — but they tend to regenerate pretty quickly once planted in the new site, and the ‘reservoir’ of moisture and nutrients in the remaining large roots helps sustain the tree during the excavation and move.

I don’t know of any scientific experiments that have been done to date to test this hypothesis — right now, the results are anecdotal — but I’m guessing that we will be hearing in the next few years about controlled experiments that prove or disprove this idea.  In the meantime, if you have been transplanting trees bare-root with air tools, feel free to write in and share your experience, and join the community that’s pushing into this new territory.

Q:  Do you use hydrogel on the roots of air-excavated trees?

A:  If a tree is being moved from one location on a site to another within a relatively short period of time (say, within a day), then hydrogel is probably not necessary.  If the tree is being moved from one site to another, and trucking or trailering is involved, a hydrogel spray and a secure tarp covering are probably advisable.  The following pictures come from Bransfield Tree Company LLC, which moved a large Beech tree last fall (subject of post next month):

Jonathan Bransfield spraying down the root plate of a tree with water and a 1% solution of Wilt-Pruf before tarping. Hydrogel was used in the backfill at planting.

The newly tarped root plate getting sprayed down with water before the tree's drive to another site.

Q:  Have you seen any mortality from this method of moving trees?

A:  There is some evidence that trees with particularly tender bark don’t do well with direct pressure from compressed air.  Matt Foti notes that two cherry trees he moved last year died; a few weeks ago he moved a cherry on his own property, and had his crew blow soil out from under the tree, aiming the air in toward the trunk from the blowout trench.  He has planted the tree out in his nursery and will watch it for the next year, to see how it respond to the more sensitive treatment.   Here’s an instance where the technology is available to do the work, but our knowledge is still catching up with the technology.  If anyone wants to do a controlled, scientific study, this species-specific question would be a great one to explore.  In the meantime, arborists doing this work will report in as they learn more.

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At New England Grows, I met Jim Doyle, one of Wellesley College‘s team of arborists. He told me about an air-tool transplant that he and a colleague performed last November at the College.  He was kind enough to send photos, and with them included this text, which I have edited only slightly:

“My colleague Don Garrick and I performed the transplant on Nov. 3rd 2009.  The reason for the transplant was that the tree, a Picea glauca ‘Conica’ (Dwarf Alberta Spruce), had outgrown its current location and was providing too much shade to the greenhouse.  An old accession tag we found told us that the tree had been planted in 1956.

The tree in its original location, quite close to the greenhouse.

Jim using the airspade to locate the root zone's outer limits.

Don digging a trench outside of the root zone.

In this and in the next two pictures, Jim removes soil from the Picea's roots.

  

Working in from the perimeter toward the trunk.

Don lifts the tree out of the hole.

Transporting the tree to its new home across campus. The tree has been laid down for stability.

The tree in its new location, with plenty of room for continued growth up and out.

During the whole process we watered the roots every 5 to 10 min.  We wrapped the roots in wet burlap for the transport.  Once we had placed it in its new home, I sprayed the tree with with anti-transpirant and we then staked it, as its new home was a very windy location on the lake.  The stakes and guys will probably be removed this summer once we can confirm that the tree has settled well enough in its new hole.”

Here’s an example of the thoughtful management of plants on a property.  This Dwarf Alberta Spruce was in good shape, but had grown out of its original location, tucked behind the greenhouse.  Moving it was a fine way to save the tree, preserve the antique greenhouse glass adjacent to it, eliminate the greenhouse interior shading problem, and revamp the area — and now the tree, in its new spot, has room to grow and is visible to the Wellesley College community.

Project site:  Wellesley College campus, Wellesley, MA

Project arborists:  Jim Doyle, ISA-Certified Arborist; Don Garrick, MA-Certified Arborist

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Another question asked at last week’s New England Grows about bare-root transplanting was “How do you make sure the roots don’t dry out?” The answer, of course, is that you water the tree you’re moving.  You water it thoroughly a couple of days before the transplant, to insure that the tree’s tissues have good turgor pressure and moisture reserves for the bare-rooting.  You take a break every now and again during the blow-out (if you’re using compressed air) and spray down the exposed roots with water.  You may spray more water on the roots — the top, bottom, and inside of the root mass — when you pick the tree up on forks to deliver it to its new home.  You ‘mud in’ the tree as you backfill, saturating the backfill soil with water to eliminate any air pockets and again, to combat root dessication.   And once you have mulched the tree well, you water still more.

Water in all phases of the operation is key to tree transplanting.

Cornell’s Urban Horticulture Institute advocates using a hydrogel slurry to hold water on the bare roots during planting.  Their excellent Creating the Urban Forest:  The Bare-Root Method describes the process of planting young trees bare-root, and is well worth reading.  The challenge of using a slurry for large-tree transplanting would be in getting a consistent coating of hydrogel on the roots (you can’t dip the root plate in a tub, the way you can with a sapling root mass) — but there must be a solution (so to speak) to that problem. And finally, aftercare is critical.  Moving a large specimen tree bare-root takes time and effort, and it would be folly to follow all the steps, get the tree in the ground, and then leave its re-establishment and survival up to chance.  Some arborists add fertilizer and bio-stimulants to the backfill, some don’t.  What is essential, again, is water.  Consistent and adequate water for the first growing season is the best way to make sure that a transplanted tree makes the transition to its new home, survives, and thrives.

Watering in a root-washed pin oak at Cavicchio's Nursery. Photo courtesy of Carl Cathcart.

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Thousands of people showed up at New England Grows this past week.  One of the conference’s principal speakers, Bonnie Lee Appleton, unfortunately fell ill and had to cancel her Wednesday talk; for a while the day before the conference it looked as if one of the two convention center ballrooms would be empty for a couple of hours.  At the last minute, NE Grows asked Matt Foti to take Ms. Appleton’s place with a talk on bare-root planting.

The talk was great — packed with information — and sent a steady stream of people to the Foti Tree and Landscaping booth to learn more about bare-root transplanting.  Matt teamed with Teddy and Mike, two of his arborists, to field questions at the booth, which had a good set of air-tool transplant photos, a continually running rough cut of my London Plane video, and two 3-inch caliper Zelkovas from Matt’s nursery. One of the Zelkovas had been dug, balled, and burlapped; the other sat with its bare roots splayed on a sheet of plastic, showing off their extension (they extended about 3-4′ on all sides from the tree trunk), uncut tapers, and web of water-collecting and nutrient-storing capacity.  Every now and again one of the arborists would spray the roots with water.

It was cool to watch visitors to the booth stop and take in what they were seeing.  Some of them shook their heads and moved on; most, though, would watch the video for a few moments, or peer at the photos and the trees and start asking questions.  Matt and Timmy and Mike rarely had a moment in the three days when they weren’t answering questions.

A couple of questions popped up over and over.   Arborists, landscape architects, designers, and contractors all wanted to know how much air-tool transplantation costs.  The answer, based on labor requirements, species, condition, and size of tree, as well as on site conditions, was that bare-rooting a tree for transplant may cost more than digging it with a tree spade, but less than digging it with the more traditional drumlaced B&B method.  Bare-rooting a tree for transplant typically preserves at least 90% of the tree’s roots, though, a claim that cannot be made for the other methods.  The more roots you save, the less transplant stress and the shorter the tree’s reestablishment period — and all other factors being equal, the healthier the tree tends to be after transplant.

The other question, also coming from arborists, landscape architects, designers, and contractors, was about taproots.  How did bare-root transplant affect a taprooted tree?  The answer is that taproots are rarely an issue, at least in this part of the world.  In New England, soils tend to be shallow.  As we know, 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 do extend vertically down in this zone, but many more run horizontally away from the tree’s trunk.

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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I just got a rough cut today of the video, shot last summer, of the moving of a very large (about 14″ caliper, 30′ height) London Plane Tree.  It’s taken a while to edit several hours of footage down to a half an hour, but it’s about done, and in the next few weeks I hope to have added commentary.  This video is from the project run by Matt Foti’s crew, aided by Mike Furgal, and it showcases the techniques used in air-tool transplanting.  I hope to be able to preview the rough cut at New England Grows, and have the final version completed by the end of February; if there’s enough interest in the arborist community I’ll sell copies.  Stay tuned.

The first of five 12-14' caliper London Plane trees being excavated with air tools and transplanted bare root in August 2009.

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To continue yesterday’s post on the bare-root transplanting of a Norway spruce at the Perkins School for the Blind in Watertown, MA:

The crew uses a heavy canvas strap wrapped securely (more than once) around the trunk, and pads the Bobcat fork bracket. This tree's flat back meant it could be pulled securely up onto the forks without tying up branches; other trees would need to be tied up for easier spading and transport. Here, the forks are poised to push under the root ball, just below the wire basket.

Rolando prunes thin fibrous roots from under the basket, to release the root ball from the ground. Most of the root mass has already been blown out.

Spruce on the move. With almost all the soil blown off the root mass, it is light enough for the Bobcat to carry the tree easily across campus. Canvas straps secure the tree to the Bobcat; Rolando rides along just in case.

Closeup of the root mass. Virtually all of the roots on this tree were quite thin, and they made a dense mat that extended about nine feet out from the tree's trunk on several sides.

Mynor had dug out the hole with the Bobcat while Sonia and Rolando blew out the soil from around the tree. This site, next to a busy campus parking lot, challenged the crew to place the tree carefully. Cars were parked just to the right of the orange barrier in this photo, and other relocated trees ringed the dish on two other sides, so maneuvering to get the tree in place was a bit tricky. It's relatively easy to spin at least a small B&B tree to the right orientation; turning an air-spaded tree requires a bit more forethought. In this situation, a bit of three-dimensional visualization was necessary to be sure that the flat side faced away from the parking lot.

Sonia and Rolando used a rake handle and tape measure to determine the root mass's depth before adjusting soil depth in the new hole.

Additional native soil is added and compacted to make a pad under the trunk. When in doubt, it's better to place the tree slightly higher in its new location than to risk it settling deeper once it has been backfilled and watered in; tamping the soil firmly under and around the roots right at the tree's base helps insure both that the soil won't subside and that air pockets are eliminated.

Rolando guides Mynor in setting the tree in the right spot. Good communication is key through this entire project, and these guys were excellent in coordinating their work with each other.

Rolando and Santo shovel native soil under the rolled-up root mat, to secure and level the tree before its roots get spread out.

Sonia and Rolando spread soil under and over the roots as they unroll them from the bundle. Note that they are using soil excavated from the site, with no amendments. Bare-root transplanting eliminates the difficulties associated with moisture transfer between two types of soil (root ball soil and soil outside the root ball), which makes establishment in its new site less stressful for the tree.

With backfilling complete, the crew builds a berm.

With the berm in place, Sonia waters the backfill thoroughly. Some crews shovel in the backfill and water simultaneously, "mudding in" the tree for extra stability and the complete elimination of air pockets. Mulch will go on this new planting next, and then more water. Note that you can see the root flare, now that the tree has been excavated from its original root ball and planted at the proper depth.

Project site:  The Perkins School for the Blind, Watertown, MA

Project manager:  Sonia Baerhuk

Project crew:  Rolando Ortega, Mynor Tobar, Santo Masciari

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The Massachusetts Arborists Assocation bare-root workshops — one in August 2008, and one in August 2009 — have been spreading word through the Commonwealth about the benefits of air-tool tree transplanting, and word is travelling throughout Massachusetts horticulture circles now.

A couple of weeks ago I was chatting with Kristen DeSouza, one of the horticulturists at the New England Wild Flower Society‘s Garden In The Woods, and she mentioned that she had passed my name along to Sonia Baerhuk, who tends the grounds at Watertown’s Perkins School for the Blind.  Kristen told me that Sonia and her crew have been using air tools to  transplant trees on the school’s grounds for the last several months, and suggested that I get in touch with her.

And so last Thursday, a couple of emails and a phone call later, I pulled in to the visitor’s parking area at the Perkins School.  Sonia soon arrived in one of the grounds department’s Gators.  She very kindly showed me around the campus, explaining that a new and large building project had required the removal of dozens of large trees.

It’s a scenario typical of many institutional sites:  a program outgrows its home, the phasing of a master plan leads to a shifting of facilities or the construction of a new building, and the vegetation on site must either be removed or relocated.  Having worked at Perkins for several years, Sonia was no stranger to this course, of events, but still, she had been dismayed to see so many large specimen trees being cut and fed into the chipper.

Though the grounds crew does most of its own tree work, over the years they have called in arborists for their expertise, and Sonia knew and trusted Matt Foti’s expertise.  Matt had told her about the air-tool method, and on the strength of his recommendation, she signed up for the MAA’s Elm Bank bare-root workshop this past August.  At it, she absorbed as much information as possible.  She came away from the day’s event convinced that air-tool excavation and transplant was the best way for her crew to relocate any salvageable campus trees.

So Sonia and her boss Rich Falzone equipped the crew with an Air Spade and an Air Knife, coveralls, eye protection, ear protection, and respirators, and began to direct the relocation of trees.

To date, the Perkins crew — Sonia Baerhuk, Rolando Ortega, Mynor Tobar, and Santo Masciari — has moved several 15-20′ Norway spruce, a fastigiate white pine, a Forest Pansy redbud, several apples, and a beautifully structured 25-30′ tall Halesia.

On the day I visited, they were ready to move another Norway spruce from a location that is slated to become a pondside patio.  Its new home would be a lawn next to a parking lot to which they had already moved a number of evergreens.  The new planting is beginning to screen the lot from adjacent buildings; over time, this grove will shade the parking lot and the walkway near it.

Sonia Baerhuk marking the new home of a 15' Norway spruce to be relocated.

Fifteen-foot Norway spruce in its original location next to the campus pond. The crew discovered that the Norway's roots were interwoven with roots from other nearby trees. This tree was flat on the side facing the fence.

Currently, the grounds crew rents compressors. These two generated air for an Air Knife and an Air Spade. Note the plywood barriers set up to prevent soil overspray onto the lawn. In this project, the crew did not dig a trench to hold blown-out soil; they simply started blowing soil out from the trunk and followed the roots out to and beyond the dripline.

Sonia and Rolando, kitted out in their PSE: coveralls, gloves, hats and hoods, ear protection, eye protection, and respirators.

Blowing soil off the roots took about three hours. Sonia likes to divide the root mass diameter into quadrants and work systematically, while Rolando prefers to work all around the tree; when they work in tandem they use whichever method fits the site conditions best.

Edges of the original B&B root ball are barely visible here; it was roughly 24-30" across. Rolando and Sonia discovered the wire basket still around it. They also discovered that the root flare sat several inches down in the original root ball.

The spruce was anchored with a thick mat of fibrous roots; the crew found virtually no roots larger than 1/2" in diameter. Here, they are pruning root ends under the eighteen-inch deep mat.

Still pruning the mat, and rolling it up toward the trunk to blow soil out from under the tree.

The root mat rolled up and bound in burlap for further blowing-out and moving.

Project site:  The Perkins School for the Blind, Watertown, MA

Project manager:  Sonia Baerhuk

Project crew:  Rolando Ortega, Mynor Tobar, Santo Masciari

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