You have to admire the forward thinking that gets a new stand of trees started while an existing stand remains; it’s a principle used more in European landscapes than American ones, and we could stand to practice it more here.  It really makes sense to extend one’s planning horizon beyond the span of one’s own life and think both in terms of tree longevity and of the needs of generations to come after us.  The idea of getting young trees established under a mature stand seems particularly apt at on a school property, where adults are fostering the growth and education of children, and tending the young beings who will one day assume adulthood.

So the failure of this planting, installed with apparently the most admirable of motives, seemed especially poignant and distressing.  The tree species selection seemed fine, but it looked as if almost every other element of a planting — root ball size, soil quality, well construction, mulch used (or lack of it), and watering — was inadequate to fulfill the aim of establishing a planting that would live and thrive.

It was impossible to miss this planting from the road below. Virtually every newly planted tree is either dead or nearly so.

From the school drive above the slope, the view is as disappointing. The pears look like the toughest of the new trees out there. Fall color in July is never a good sign, but at least they still have leaves. The zelkovas are mostly bare.

That pile of soil in the foreground is the native soil on this New England upland slope, thin and sandy, with little organic material evident. It appears that the new trees were planted directly into this soil without amendment -- which is fine, as long as the planting crew worked on the root balls to make a rougher interface between root ball soil and native soil. Because water will only move from soil of one porosity to another when the soil is saturated, and roots follow water, you want to scuff up the walls of a root ball to make a less distinct interface between the two soils, and to encourage water and roots to cross the interface.

Tiny root ball? Perhaps. For a 3" caliper tree like this , ANSI standards call for a 32" diameter root ball. The well on this root ball is about 18" in diameter, so it looks as if the root ball is small -- but it may simply be that the well itself is inadequate. Wells should be built outside the root ball wall, so that water is held over the root ball and over the interface between surrounding soil and root ball soil, and so promotes root growth beyond the root ball. Not to mention that these trees were placed right at the drive edge, where their root cannot spread out under the asphalt, and the weight and pressure of plowed snow can tip them...

Another tiny root ball, with a mini-well. The well is very loosely constructed; water has broken through and run down the sandy slope, leaving the tree high and dry. This photo makes me thirsty.

All of the trees are planted on sloping ground, but hardly look it -- another indication that root balls and water wells are too small. Got mulch, anyone? Particularly in this type of sandy soil, a watering schedule and at least a temporary irrigation system (set up to last and run through the first growing season) would help establish the trees. Planting like this has consigned what were once good trees to the chipper.

Egh. More of the same.

What good can be said of this planting?  Well, again, the idea of starting a new generation of trees in an established stand is an admirable one.  The tree’s root flares appeared to be in the proper relation to the surface of their root balls.  Otherwise, it seems to me that this planting is a cautionary tale:  against contractors who do not know how to plant properly, against too-small root balls, poor soils, substandard planting practices, bad tree wells, the absence of mulch, inadequate provision for watering, and inadequate watering itself.  The information on how to plant and foster trees is readily available, so the question may be how do we broaden people’s awareness of it, and their awareness that trees are living organisms rather than tall pieces of furniture?  Any ideas?

I was interested in the root configuration on this six-inch caliper red maple.  A mass of fibrous roots wrapped closely around the tree’s trunk, much like cotton-candy filaments spun around a paper cone.  Looking at it more closely, I found that the fibrous roots grew out of thicker woody roots, some of which had been cut during the tree’s original ball-and-burlapping, and some of which, growing since that operation, were circling the trunk.  Take a look:

Fibrous roots circling the six-inch red maple trunk.

Pulled away from the trunk, the roots clearly are circling it. Over time, as the tree grew in girth, these roots likely would have constricted the flow of nutrients between root mass and crown

Here's the tree's underside. Note the girdling root snaking on top of the big torn root facing the camera, and the curiously self-contained look of this root mass. The tree's problems likely began early in its life.

Not every B&B tree has these problems, and in those that do, not every rooting problem can be remedied at planting time.  Judicious treatment — looking for circling roots that can become girdling roots, cutting back girdling roots and cutting or redirecting circling roots, roughing up the sides of the root ball, removing or cutting down wire baskets, pulling down or removing burlap — can go a long way in helping B&B trees establish better in the landscape, and in remedying problems that threaten a tree’s long-term health and viability.  For more discussion on root issues affecting B&B trees, check out this post on Matt Foti’s station at the MAA’s Elm Bank bare-root workshop in September 2009.

Here’s what Mark had to say about the Weeping Norway Spruce they recently moved from Baker Valley Nurseries (with light editing):

“We moved a 25+ year old Weeping Norway Spruce that has resided in Baker Valley Nurseries in Rumney for the duration of its life.  This tree stood 10-11 feet tall and at least 12 feet wide on one direction.  The last time this tree was root pruned with a spade was 10 years ago.

Through the spading process we could clearly see where this root pruning occurred.  All said and done we were left with a 25-30′ wide root system…You cannot see that in these pics real well, as we had all the roots coiled up into harnesses and sitting atop the root pan.

I helped Piscataqua with the digging of this and am told so far it looks great in its new home on the coast.  Just to dig and get the tree in the truck took about 4-5 hours with 2 of us spading, and then 4 of us to get the tree in the truck which was actually the worst part.”

The tree before excavation.

Branches tied back to permit easier blowout.

Leader wrapped in burlap to protect it during excavation and moving.

Deepening the excavation.

Root plate covered in wet burlap for the pickup and move.

Guiding the forks for the lift.

Confirming a balanced and firm placement on the forks.

Guiding the lift.

A final spray-down before transport.

No photos yet of the tree in its new location, but when they come in I’ll post them.

Tree and equipment supplier:   Baker Valley Nurseries, Inc., Wentworth, NH

Moved by:

Piscataqua Landscaping Company, Inc., Eliot, ME  (Booth Hemingway and Travis Wright) and

Belknap Landscape Company, Inc., Gilford, NH (Mark Smith)

Well, it wasn’t there.  We turned around, backtracked along the pathway, and came upon a grounds crew working on a plaza installation.  We stopped and met John Olmsted, Manager of Landscape Operations, who told us that the Spruce had died.  He said that despite its loss, the arborists had recently transplanted a Sugar Maple, two Kousa Dogwoods, and an American Smokebush bare-root.

The Dwarf Alberta Spruce didn't make it, but this spring-transplanted Kousa Dogwood may well thrive in this spot.

Later, Jim Doyle told me that he thought they had moved the Spruce to a too-exposed location.  It seemed to fare well through the winter, but in March had turned brown and had to be removed.  We speculated that the move from a very sheltered spot to an open waterfront location might have placed too high a demand on the plant.  It might have survived the dangerous phenomenon of frozen soils and warm air had it been wrapped in burlap, but it’s impossible to know.

Nice trunk flare on the newly transplanted Sugar Maple at Wellesley College.

What is heartening is that the Spruce move came about because Jim and Don took a chance — and though the risk didn’t pan out, the College believed in the possibility of success, and authorized the bare-root moving of four more plants.  When it comes down to a choice, especially on a large campus, between moving or destroying a tree, the opportunity to move and save the tree may make sense.   Actively managing a landscape — especially one with valuable mature trees —  requires this kind of decision-making, and newly available technologies can give greater flexibility in the move-save debate.

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.

“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.

  

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

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.

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.

Good idea – but woops! The minimum standard for root preservation is to keep 10 inches of root mass diameter per caliper inch of tree. For these trees, that would spell at least 360-inch diameter root masses. Because the trees are so close together, their roots overlap significantly — but still, 360 inches is thirty feet of diameter.

This 18-footish enclosure takes a tad too much root; the country club will almost certainly be watching these trees decline and die over the next few years (and they may well drop dead branches onto the parking lot, or cars in it, in the process).

The idea of saving a mature tree is a good one, as long as the tree’s actual requirements for continued healthy life are met.   Now that we have the tools to see how large a tree’s root mass really is, it’s much easier to see how big the unimpeded area around it has to be for the tree to survive happily and to thrive.

Giant root mass, 30 feet across, preserved by air excavation. Note the trunk's heavy padding, and pigtailing of the roots.

So that's what a beech's roots look like. This tree had been transplanted with a tree spade about 20 years ago, and it was possible to look under the root plate and see where severed roots had sprouted out.

The 30-foot high tree being lowered onto a specially rigged trailer for transport.

After the tree had been loaded onto the trailer, its roots were covered with burlap and sprayed down for the ride to its new home.

This post is just a teaser; next spring after the tree leafs out I’ll write a post on the  whole air-tool transplant operation, and give all the who’s, what’s, why’s, hows, wheres, and whens.  Stay tuned.