What trees need us to know

Last week at New England Grows, while Toby was manning the table for the Ecological Landscape Alliance (its shiny new name hasn’t made it onto the website yet, but the ELA is an outstanding organization, and so is their material), he struck up a conversation with Jeff Ott, owner of Northeast Shade Tree in Portsmouth, New Hampshire. Jeff told him about a workshop he’ll be giving on March 6 for landscape professionals; it’s called “Tree School for Landscapers; The Built Landscape From An Arborist’s Perspective”.

The Old Elm on Boston Common, 1876
Courtesy Boston Public Library via Flickr; Creative Commons License: http://creativecommons.org/licenses/by-nc-nd/2.0/deed.en

Jeff, who has been an arborist for the last 36 years, had the great good fortune to work with Alex Shigo — probably the most influential tree researcher of the 20th century. Recognizing that more intellectual cross-pollination between arborists and other landscape professionals would benefit the landscapes on which we all work, Jeff decided to put together this workshop. The timing is good, before the spring planting and construction season gets rolling, so I’m aiming to go, and hope that other landscape architects will seize the opportunity as well.

Here’s the Tree School announcement.  Don’t be alarmed about the absence of an address:  you send your registration form and check ($75) to:

166 Clinton Street, Portsmouth, NH  03801

And here’s the Tree School Agenda, which outlines what will be happening through the day.  Contact Jeff if you have further questions; he can be reached at jottphc@gmail.com, or by phone at 603-463-7512.

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Root work

Contractors, arborists, and landscape architects in Massachusetts would do well to check out the Ecological Landscaping Association’s September events list.  The ELA is offering a number of really good workshops, on topics ranging from Boston-area restoration projects to the use of fire in landscape management, as well as a two-part, two-day workshop on root issues.  

One day of the root work will focus on soils(f you’ve read any of this blog, or Taking Place In The Trees, you’ll know that I’m interested in roots.)  In the air tool workshop, entitled At The Root: Air Tools Workshop, Rolf Briggs and Matt Foti will be talking about using air to work in the root zone, to decompact soils, to transplant trees and shrubs and also about how to plant nursery-grown stock properly.  

Matt and Rolf have done a similar workshop for the Mass. Arborists Association in the past, and Matt holds an annual workshop on proper planting techniques.  Being able to see what a root system looks like is eye-opening.  Learning — not just from written specs or a generic tree-planting detail — how a tree or shrub should be planted is essential, and well worth the price of admission.  I have been to at least three of these workshops, and learn something new at each one, and so can say that this workshop is one every landscape architect who designs plantings, and every contractor who sells plantings should attend.

Michael waters in a hemlock whose root flare has been excavated with air.

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Boston hemlock

The other day I was on Beacon Hill and spotted this mostly dead hemlock tree, completely swathed in Boston ivy:

Though this hemlock tree on Beacon Hill is dead, its stripped-down structure maintains usefulness, as Boston ivy covers it entirely with foliage.

Perhaps the owners were simply neglecting their courtyard garden, but I like to think that they saw the mature tree’s size as an asset to the place, and decided to use the deadwood as an armature for another plant, and to use the resulting ‘hybrid’ as a garden element.

I have seen this strategy used with other trees; an ancient, mostly dead apple through which a vigorous rose climbs and blooms, tiny dead crabapple that hosts a clematis vine, and a couple of thriving Norway maples through whose canopies wind equally thriving wisteria vines.

We see bittersweet and poison ivy taking advantage of the height and sun exposure offered by trees; why not use that principle and foster the growth of ornamental vines over dead trees, or, as in the case of the Norway maples and wisteria, let one aggressive species provide a platform for another aggressive species?

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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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Dappled willow

About ten years ago, I noticed a mild fad rev up in the gardening world; all the garden centers around here started carrying Salix integra ‘Hakuro Nishiki’, usually trained into standard form with a 3-4′ high stem and a pompom of foliage at top. Hakuro Nishiki, also known as Dappled Willow, is a fast-growing, twiggy large shrub/small tree with variegated white and light green to pink leaves, and it lights up a garden with its foliage, which is profuse and almost aggressively healthy-looking.

I’m fond of these plants, though they certainly need to be placed with care. They like full sun, but can deal with some shade. Because they grow so vigorously, it’s a good idea to commit to pruning them every year or so, to keep them in bounds. Actually, I can see how sculpting them in various ways each year might be an interesting exercise — not something you’d want to do with most plants, but this one seems malleable enough to allow some experimentation.

I have written earlier about L. and A., my excellent clients on the North Shore, who enjoy developing and fostering their landscape. Several years ago L. bought a Dappled Willow for her perennial garden. It’s not a standard form; instead, she’s keeping it pruned low, to keep it in scale with other elements in the garden. Here’s a photo of it in leaf:

This plant is about thirty inches high and wide, and is kept as a mounded shrub with pruning.

And here’s a photo of how L. prunes it to keep it contained to this form:

Every year L. cuts this Dappled Willow back hard, to keep its vigorous growth contained in a form that works for her perennial garden.

I have wondered what these plants look like unpruned, and last week got to see one. If the willow in L.’s garden looks like a contained explosion, this one looks as if the top blew off the container:

Perhaps the owner of this plant didn't realize what level of attention Hakuro Nishiki was going to require annually.

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Renaissance view

Don’t you love this photo? Toby Wolf took it at the Crane Reservation in Ipswich, a property of The Trustees of Reservations. He said that for him it has the quality of an oil painting; I agree completely. It has that same dark/light/dark sequence, that same frame/focal point/background flavor as a painting by an Italian Renaissance painter.

At the Crane Reservation, Toby writes, “It looks like The Trustees have deliberately maintained the opening to the view, and that the late-afternoon light, raking across the marshes and the bark of the trees, is what makes it work. I like the light on the ground-layer plants.”

The whole ravishing photo.

Here’s an example of landscape management supporting a design intention. Sometimes we design places with stone, wood, earth, metal, and plants; sometimes we design views, and tweak a visitor’s perception of a place by what we leave in, what we remove, and how we frame and focus what they see. Obviously, a photograph can be manipulated to do these things, but sometimes a photograph simply records a perception that has been shaped by others, as The Trustees have apparently shaped the Crane Reservation view.

A view framed by dark elements, a view into a light space, a view toward water, a view toward curves — what a pleasing combination. I want to take a bite out of this photo.

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If a tree falls in a garden…

The massive four-stem Norway maple that blew down in high winds last week.

Following up on the list post item from June 9, about what to use to replace a lost Norway maple: it will be a honey locust (Gleditsia triacanthos inermis ‘Shademaster’), placed slightly upslope from the Norway stump.

Last week I visited the North Shore seaside site (where last year we revamped the drive court planting and added bamboo and holly for property line screening; to read about those projects, see Refinement and Air Spade In Action) and saw the spatial effect of losing this tree.

Surprisingly, the loss wasn’t as bad as I had thought it would be. The tree’s canopy had taken up a huge amount of space and cast deep shade over quite an area. It had screened my clients from an unappealing view of the corner of their neighbor’s house — but also from a wider view of the Boston skyline in the distance. Now the horizon is wider; they’re going to have a spectacular view of the city’s July 4 fireworks. While the neighbor’s house is unfortunately visible for the moment, the honey locust will mitigate that view. A younger specimen maple just over the property line, which had been hidden by the larger tree, looks healthy, and helps provide a perspective-focusing foreground to the far horizon.

Fortunately too, while the tree provided shade over a wide area of the site, much of its underplanting consisted of junipers and taxus, which should benefit from having more sunlight. The redtwig dogwood, azaleas, and hydrangea will think a bit about how much they like being exposed, but I think they’ll adapt. Even the little spring shade garden should fare all right, protected as much of it by a dense shrub planting from full sun exposure. Many of the herbaceous plants in it are ephemeral anyway, showing up in early spring before any trees leaf out, and fading back as foliage emerges above them.

Shade cast by the now-gone Norway maple protected the little spring garden and its ligularia circle at the path's end.

Our biggest concern for this newly sunny area is the ligularia bed. This bed, banded with a circle of bluestone, makes the southern terminus of a sightline through the tiny spring garden. The ‘Britt Marie Crawford’ ligularia, with its chocolate-brown foliage and golden spikes of flowers, makes a ravishing dot at the bottom of the exclamation point. And it’s a shade lover.

Ligularia 'Britt Marie Crawford' in its circle bed.

It may not be at all happy to be getting sun all day every day. My hope is that it can handle it well enough for long enough to feel relief from the kinder, more dappled shade that the new honey locust will eventually cast.

This site has seen several mature trees come down since last year; neighbors next to the drive court removed a large maple and a lovely S-shaped pine, an ailing ash tree got taken out, and a graceful Russian olive specimen, some 20 feet tall, blew down in the same storm that took the big Norway maple.

Each subtraction has shifted the sun/shade proportions, and each will affect the growth and health of the surrounding area. This kind of change requires adaptation both by the plants and by the owners, and provides opportunities for new ways of seeing a familiar place.

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Pollen’s only part of the story

ZZZZZZZZZZZZSSSSSSDDDDchew!! Excuse me; Toby’s photo of the pollinating pine in that last post just makes my nose tickle.

His points about pollinating trees make sense to me; wind-pollinated trees are different in nature from insect-pollinated trees, and have quite different effects on those allergic to fine particulates.

I have to say that Mr. Ogren’s original Op-Ed piece stood out as much for its hypo-allergenic focus as for its assertions about what trees do get planted in cities. To set the record straight, a number of the plants he mentioned (both favorably and unfavorably) — box elder, mulberry, silver maple, willow, cottonwood, and even red maple — are considered either outright weed trees or are simply weak-wooded and would never pass muster for planting in dense urban areas. More often than not, most of these trees volunteer in the city, and are able to thrive because they are wind-pollinated, produce a lot of seed, and are able to grow quickly and under conditions that would stymie less tenacious trees.

Landscape architects and arborists working in cities tend to avoid these plants for street tree plantings; in fact, I would think of using some of them — if any — only on larger sites where space was not an issue, where I wanted fast and effective growth, and where there was no chance that they would invade other areas. Municipal lists of acceptable street trees are actually, quite limited, as the piece points out, and mainly include slower-growing or more structurally sound trees than some of these worst culprits — the criteria for street tree selection in a city have to take into account those trees that have relatively reliable structure and habit, can deal with difficult soil, exposure, and moisture conditions, and that don’t create walking hazards with heavy fruit set.

What struck me most, after reading Mr. Ogren’s piece, was the realization of how much vegetative biomass there is in cities, despite our best efforts to pave wherever possible. The ocean of pollen we swim in every spring and summer comes from volunteer as well as planted trees, shrubs, grasses, and forbs, and reducing the pollen count in any area feels a little bit like setting aside a piece of the ocean to make a freshwater pond…

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Herbie

I just wrote a post on Herbie, the champion American elm in Yarmouth, Maine, that was taken down last week after a life that spanned more than two centuries. The post, at Taking Place In The Trees, included several photos I took the day before Herbie came down. In his prime, Herbie was the largest American elm in New England — 110′ high, 120′ wide at the crown’s widest point, and 20′ in girth. When I saw him, more than half of his largest limbs had been removed, but the tree’s presence and majesty were unmistakable.

Herbie the American Elm, in his prime.

A field count of the rings on Herbie’s trunk indicated that the tree was at least 212 years old. This was a tree that largely defined the genius loci of its neighborhood. It filled the corner of a private yard and marked the intersection of two streets; it cast high shade over a wide and fortunate area.

It’s not difficult to extrapolate lessons from Herbie’s presence and longevity, lessons that might inform how landscape architects design and advocate for planting spaces. I can think of these lessons:

1. Plant trees! They provide cover, coolness, oxygen, and identifiability to a place.

2. Plan for the long term — aim to foster a tree’s growth for decades, not just for years.

3. Design for root space — bare-root transplanting of large trees shows us how trees benefit from space in which to grow, and how far from the trunk their roots need to grow to add crown growth. Push those developers, homeowners, and city agency officials to allocate more space for subgrade growth; it’ll pay off in happier, healthier trees, and broader shade canopies.

4. Remember how big trees want to get. Putting a large-scaled canopy tree in a slot of soil better used for skinny grasses won’t give you the tree you’re looking for; it’ll give you a tree that whimpers for a few years, declines, and then dies. Scale your trees to your site (aiming for as big a planting site as possible — see 2. and 3.)

5. Shoot for size. People love the giant, and are more apt to preserve and take what they love. A large tree builds its own constituency, which helps when you’re trying to keep nature from being overtaken by pavement. If you want people to engage with nature, give them something with which it’s easy to engage. (Keeping in mind 4.)

That’s for starters. What other lessons do you see in Herbie’s story?

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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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