Hemlock root flare excavation

It has been a while since I’ve written about root flares. I got some photos from my friend Carl Cathcart the other day, showcasing the excavation of a hemlock root flare. This tree is one of a hedge of 7-8′ tall hemlocks planted two years ago. Its owner had noticed that while the hedge wasn’t failing, it wasn’t exactly thriving, either. He called Carl, a Consulting Arborist, in to inspect the situation.

Carl zeroed in immediately on the base of the tree, and with a little hand excavation discovered that the hemlocks were sitting at least four inches too deep in their root balls. It has been customary for years to plant balled and burlapped trees so that the top of their root balls sits at or slightly above the finish grade around them. Cultivation practices in the growers’ nurseries have changed since that technique became the standard, though, and now it is necessary to check each root ball to make sure that root ball soil is not covering a tree’s root flare. A buried root flare — whether it is buried with root ball soil, compost, or an excess of mulch post-planting — spells trouble for a woody plant, and can be the cause of a tree’s failure to thrive. Small leaves, shorter-than-normal annual twig extension, and thin foliage can all be symptoms of a buried root flare. Root flares are not roots and are not adapted to life under the soil surface; they are part of the tree’s aboveground trunk, and typically need to be exposed to the air.

The in-field solution to this problem (should the excess soil not be removed in the nursery) is to excavate the root flare onsite during project planting. This task should be done before the tree is planted, so that the flare is planted at the correct grade; unfortunately, many contractors are not even aware of the issue, and will not have included time for root excavation in their bid. Here’s where landscape architects can make a major difference in the longevity of their project’s woody plants, and where contractors can distinguish themselves from the competition; LAs aware of the need to excavate root flares should include that requirement in their bid sheets for contractors, and contractors aware of that need (whether they are in a bid situation or not) can use this task, and the benefits it brings to the planted landscape, as a compelling selling point.

When root flare excavation doesn’t take place when the plants go in the ground, the signs of tree stress will likely show up within a year or two. At that point, hand excavation is still possible, but air-tool excavation usually will be more efficient.

When Carl identified the problem, he advised the homeowner to have air-tool excavation done. Matt Foti of Matthew R. Foti Tree and Landscape sent over a crew to carry out the work; Carl’s photos illustrate this post-planting process nicely.

The arborist has tied up the hemlock's branches for easier access in to the root ball. In this photo some of the soil has been blown away already.

A compressed air tool blows off the root mass. Just visible behind the tree is a plywood barrier that helps keep airborne soil from covering the surrounding plants.

The root flare has been uncovered; note the soil line about four inches up from the root mass. When you see side branches at, just above, or even emerging from below the soil level you can suspect a buried root flare. Carefully scraping away soil at the tree's trunk will indicate if further excavation is necessary. Now that the root flare is exposed, it is possible to see the girdling root that has formed on the trunk's left side.

The girdling root has been cut off, preventing any further vascular constriction in the root coming off the trunk and heading toward the photo's lower left corner.

With the root flare exposed and girdling roots removed, planting soil is blown or shoveled back into the excavated area at the correct grade.

The last step, before untying the branches, is to water the excavated area thoroughly, to rehydrate roots and to eliminate any air pockets in the root mass.

Project site: Private Residence, Sudbury, MA

Consulting Arborist: Carl Cathcart, A Plant Healthcare Consultant
Arborist for root flare excavation: Matthew R. Foti Landscape and Tree Service, Inc.

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Deskside greenery

Cattleya in bloom; Ripsalis in background

Another grey and cold day in a long, cold month. Going to my desk and working is a good antidote to the gloominess, especially when the Cattleya next to my drawing board blooms (as it did last fall), or the Ripsalis in the window each January reliably turns from a mop of green string into a mop of green string and yellow confetti. Each plant has its own delicate flower fragrance, which rests quietly in the air until someone walks through the room and stirs up faint currents of deliciousness. It’s a good reminder to use scented plants in the landscape.

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Deskside landscape

The upside.

Years ago, a friend lent me a copy of this originally tiny ad from Nature magazine; clearly, it had already been copied and enlarged quite a few times before I got a copy of the friend’s copy. I keep it next to my desk, sometimes for encouragement, sometimes for a laugh. When a different mood strikes, or I need to step away from the desk after too long there, I flip the FomeCor placard over to see this other image:

The other side.

When I do that, clearly it’s time to take a walk outside and see what’s happening in the natural world, or even just to pat the cat.

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Landscape Architecture winter article

Every month Landscape Architecture Magazine arrives in the mailbox, and some months I look through it quickly for pieces that catch my eye. Other months it has to go on the stack of periodicals next to my desk until I can pick it up on a slow day.

The 2009 series on field sketching was a dandy one, and I found myself pulling out each of those articles to save. One of my favorite things to do is to look at process art — the work that shows you the inside of someone’s mind — so I dawdled over these issues. It was inspiring to look at different sketching styles and to read each landscape architect’s approach to the materials, subjects, conditions, and opportunities of sketching.

The January 2009 issue of the magazine, which I only just recently read, had a fine piece on designing for the winter landscape. What struck me about this piece was its tying design to maintenance. Anyone who has designed a place that gets regular snowfall knows the challenges of dealing with the need to move snow, of coping with ice, and of accommodating the freeze-thaw cycles of every winter. This article, written by Adam Regn Arvidsen, outlined some fairly commonplace tactics for designing in northern climates: including a basic inventory of a site’s winter maintenance needs, considering what happens to grout when it is exposed to moisture and cold, paying attention to pavement textures and slopes in areas where ice might accumulate.

The bit that most appealed, though, was the sidebar called “Quick Tips from Winter-Savvy Landscape Architects”. Arvidsen distilled suggestions from landscape architects in Vermont, Michigan, New York, Minnesota, and Maine into a useful tip sheet, with ideas about communicating with winter maintenance crews about design intent, using darker paving materials that will heat up and help melt snow, and avoiding evergreen plantings that might hang over cars or walkways, as the shade they make can encourage ice to form. (I’m always inclined to plant shrubs and trees fairly far back from pavement that’s going to get plowed, and instead use tough, blocky herbaceous plants, like peonies or hosta, that can hack getting snow dumped on them.)

These things all make sense, and as nuts-and-bolty as they are, consideration of this sort of practicality can lead to the kind of project detailing that lends ease and comfort and an air of gracious inevitability to a designed landscape.

Photo from Flickr, courtesy of the Chemical Heritage Foundation.

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Air tool transplant video

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 in Wellesley, MA. 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 landscape architecture, architecture, or arboriculture communities 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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How we see and how we say it

One consideration in how we define slope — the audience to whom we’re communicating. When I’m discussing the pitch of a walk with another landscape architect, I’ll talk about it as a percentage (“From the wall to the driveway the walk slopes at 3 percent, with a consistent 2 percent wash”) When a contractor looks at a slope, he tends to see it as a ratio (“So I’ll set the stones to slope a quarter of an inch per foot, then”). This switching back and forth was confusing to me at first, but then I realized that the language (slope) is the same; it’s simply a matter of mastering the various dialects (ratios, percentages, decimals).

(Several years ago I had a meeting with one of the chief engineers on Boston’s Big Dig, about some grades one of the downtown tunnels. We chatted for a while, and he batted around elevation numbers with amazing facility. For me, physical slope is easier to visualize than numbers, and I still work at making the conversion from physical form to numeric form. I asked the engineer how he understood slope — as form, or as numbers — and he told me that the numbers were an easier way for him to conceive of it. He could read the slope simply from seeing the sequence of station numbers. It was remarkable to me that he could envision the nature of the grade this way, and showed yet another way of conceiving of slope.)

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Air tool observations

Matt Foti took these photos from last week’s big transplant project, and they illustrate some useful points.

Air-tool excavation is a very messy process, and it bears mentioning again that eye, ear, head, and face protection are really necessary. Mike Furgal is wearing a face mask here; a respirator would give him even greater lung protection. Blowing a good sandy loam is one thing; when pebbles and small rocks show up in the soil they become missiles, so long sleeves and pants should also be worn.

Here is what a well-tied tree looks like in transit. Note how the roots have been carefully pigtailed, and tiebacks to the tree's trunk are done neatly and professionally, to preserve the roots during excavation and in transit.

This project took place in late July, during a week of 85-degree heat. Leaf turgor pressure was maintained throughout by the trees themselves (aided with some in-process watering).

Keeping the pigtails neat from the start makes unbundling and spreading the roots fairly easy. The tree is now resting in the crater dug for its new home; the crew will unbundle and spread the roots out radially, pack soil underneath them to help level the tree, and backfill, water, and mulch the transplant. Using a forklift allows the arborists to look under the root plate and gauge its bottom profile, which helps in shaping the floor of the planting crater.

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Here’s why to plant bare root

One reader wrote in with this comment to my last post:

“It would be no good to specify bare root unless you were thoroughly acquainted with the land – soil, ledge, utility lines, for example – and spreading roots of other trees.”

And my answer, because there’s a lot to it:

Actually, bare root is good just for the reasons you enumerate; it’s much easier to plant roots alone than it is to plant a big slug of soil encasing a plant’s roots. And landscape architects, contractors, and arborists have ways of dealing with the issues you mention.

Contractors are required to call Dig Safe (http://www.digsafe.com/) to locate underground utilities on site before any excavation begins. The mis-location of utilities has been known to happen, but excavators are (ideally) careful about how they dig and about stopping when they hit something. Accidents can and do happen, but safeguards have been worked out to minimize their occurrence. (We had a little excitement at last week’s transplanting site over a gas line — apparently DigSafe found one gas line and marked it, but didn’t realize there was another several feet away. The mini-excavator found it — without breaking it — and DigSafe was called out to mark its course immediately.)

Irrigation lines, visible in some of the photos from last week’s posts, are considered expendable/fixable during a construction project. They are relatively flimsy and they run everywhere under many projects, so it is understood that they may be broken (even a shovel can break one), and will be fixed after construction and planting have been completed.

Bare-rooting a tree or shrub for planting — regardless of the surrounding soil type — often is better for the plant than planting it in a soil root ball. When one type of soil is introduced to another, as when a clayey soil root ball is placed in a sand/loam soil, the interface between those two types of soil resists the movement of water from one to the other. That means that if a clay root ball gets watered in thoroughly, water may not move so readily into the sandy loam. What incentive does the root mass have to move beyond that interface and thus into the sandy loam? Not much. Opening up a root ball and mixing some of its clay with the surrounding soil in the wall of the hole will help, but still — with a bare-root plant that issue is a non-issue. Even with a poor soil, it’s easy to mix some planting loam in with the surrounding soil (again, you want to mix, not simply dump a pile that will give you that same resistant interface) and plant the bare-root tree or shrub in the mix; doing so will make it possible for the plant’s roots to reach as far as they have to for the moisture they need.

it is a tendency, unfortunately, of many planting crews (especially on very large jobs where speed is of the essence and there may be little job training for laborers) simply to push the burlap on a root ball down just below the surface, or in some instances to leave it tied in place before backfilling. Natural burlap eventually will rot, but it can take years, especially given the subsurface soil environment, where the burlap is protected from the atmospheric oxygen and UV light that breaks it down so readily in the nursery. In the meantime, that burlap constrains root extension into the surrounding soil, and can contribute to the roots turning back in to the root ball, which affects the growth of the whole tree. So — another reason bare-root is a good approach: no burlap to fool around with and to constrain root growth.

As for ledge: You’re unlikely to know the location and profile of subsurface ledge until you start digging. That’s just the way it is. Again, though, the presence of high ledge (that is, ledge just below the soil surface) argues for using a bare-root planting method. Since tree roots typically live in the top 12″ of soil (sometimes 18″, and sometimes deeper, given the plant genus and the depth of good soil), and tree root balls can be as deep as 36″, planting a tree with soil around its roots means that you have to accommodate that root ball. Sometimes you can slice off its bottom with little ill effect on the roots. Sometimes you can’t. With a bare-root plant, you don’t have to jimmy around so much with adjusting the height of the root ball. Certainly, you’ll have to be sure you have adequate soil depth to plant the roots themselves (spreading them out radially, as they typically need to grow), but bare-root planting gives you much more flexibility in this regard.

OK. That’s it for this post, because I have to hit today’s design deadline, and this was a digression from working on it. Sorry about the lack of photos on this post; next one will have a set of really good ones, courtesy of Matt Foti.

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Another air-tool bare-root transplanting

Here’s a series of photos from an air-tool transplant project executed last week by a crew from Matthew R. Foti Landscape and Tree Service of Lexington, MA.These guys have been using air tools to bare-root trees for some time now, and they have refined the process pretty skillfully.

Shown here are a very large treeform Taxus and a smallish Cornus kousa. The Kousa Dogwood had been planted only about 8′ away from the Yew, and probably had been sheltered by it in its early days. At this stage, though, their crowns had been competing, and a revised landscape design gave further reason to spade out and move both plants.

Taxus and Cornus kousa planted closely together, as part of a larger planting that has already been dismantled.

The Bobcat has dug a trench, and the crew is blowing soil into it. Note that the Yew's branches have been tied up to keep them out of the way.

Taxus is a deeply rooted plant -- notice the trench depth, and presence of roots in the lower part of the mound..

Soil and rocks fly during the process, so eye and ear protection are essential. The white jumpsuits keep these guys from getting covered with soil (color is optional).

Bobcat continually takes blown soil out of the trench and stockpiles it.

Double-teaming a soil clod. Pushing the nozzle down into the root mass helps loosen soil inside it.

Pigtailing the roots -- tying them in long bundles -- helps keep them protected and out of the way.

Twine holds the pigtails together; when the plant is ready to move, twine can also be used to tie the pigtails back to the trunk, to keep them from dragging during transport.

Progress shot. Look at how deep the trench is. The Taxus is nearly ready, and shortly the crew will move on to the Cornus kousa; when both trees have been blown out, they will be separated and moved to new locations.

The following week: Taxus in a new spot, looking relaxed and healthy.

Final shot. Asymmetry in the Taxus crown reflects its previous location in a larger planting.

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No photos here

What is a landscape architect doing writing about these methods of tree planting and moving? Well, for one thing, I don’t like to waste woody plants. Planting an ingrown-root tree (or even a healthy one) in a new landscape without attending to the tree’s requirements — for rooting space, for decent soil porosity, for adequate moisture, for sufficient gas/air exchange at the root flare, for sufficient light, among other things — can lead to the tree’s being stressed, declining, and dying in relatively short order (a typical urban street tree lasts 7-10 years, and is in decline for most of that time). That seems a waste to me.

A tree represents a lot of energy. A tree is a system, as well as a component in a larger system. And my design work takes place in a larger system, too — that commercial system, where clients hire me to make comfortable, beautiful, gracious outdoor spaces for them. The more knowledgeable I am about these big, organic, living design elements, these systems, the better my built projects will be, and the more sustaining and sustained they will be, as well. If the best advertisement for a landscape architect is the landscape we design, then it makes sense for us to know a lot, and to use what we know, about the biggest elements we use in that landscape.

Wait’ll I start writing about water….

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