Tilted planes

To digress just a little from the line discussion: That Parc Citroen photo puts me in mind of the Cornell Arts Quad, around which are ranged some of Cornell’s most historically and academically significant buildings. The Arts Quad is huge (obviously not what it has in common with the Parc Citroen lawns shown), and there is a several-foot (eleven feet?) grade change from east to west, along its short axis.

Cornell Arts Quad looking north to south. The tipped plane displays the lawn more prominently to those walking along the west side and looking east, as an open box of candy looks more appetizing when held at a slant to display its contents better.

When I was a student there in the late 80s, and in the throes of learning how to analyze sites, I realized that the Arts Quad’s tilted plane created a perceptual wall for anyone walking along the west side, looking east and uphill. Standing at the bottom of the lawn and facing east, your eye perceives more lawn even than is actually there, because the plane is slanted rather than flat. In Parc Citroen, the tipped planes of lawn feel similarly more available to the eye from the walks along their low edge.

Using this kind of quiet grade manipulation can let you create a sense of greater green space than may really be available. Horizontal planes give you two axes — horizontal and vertical — to read, while tilted planes give you a more complex experience. I think that controlling the ground plane’s edge makes the experience more readable, as in this Halvorson-designed tilted plane at the Boston Federal Reserve Bank,

Tilted plane of lawn at Boston's Federal Reserve, with South Station behind. This cylinder of stone and grass is actually part of the Fed's security system -- no one can drive a truck through it to hit the bank's glass walls, just to the left. But you don't read it as a giant bollard; you read it as a big pad of lawn, elevated and held out to your eyes on a stone tray.

or at Park Citroen. Where the plane continues to buildings (which accommodate the grade change), as in the Arts Quad, the effect is more subtle.

Now that's a controlled edge.

Manipulating the ground plane with a wash is a fine way to tweak how a space is perceived, and to give it more quiet complexity.

Cornell Arts Quad photo taken by Anjum and supplied courtesy of Flickr.

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Hold that light a little closer, please

I tagged trees for a project last week at Millican’s Nursery and swung through Concord, NH, on the way back. A through-building alley off Pleasant Street (the main drag) led to Bicentennial Square, an eclectic in-block park built in the 70s and updated in the 90s. It has quite a mix of elements: brick waterwall, the back of which is a low stage; granite boulders carved into sculptures and seats; a stone tortoise; a tiny grove of trees, cobble, brick, and Goshen stone paving, and even a small coffee shop’s outdoor seating. Shade and the sound of rushing water made it an oasis in the hot town.

Several little lanes run into the Square, and you get a sense of the ad hoc historic accretion of buildings and byways from which it developed. I spotted these lamp posts along one of the lanes, and wondered who put them in and why so close to the building?

I understand the bollards protecting each lamp post, and wonder what the post footings look like.

I don't think that anyone makes globes with flat heads for this purpose, so each of these globes is tipped forward just a teensy bit. One more inch away from the building and they'd be perched level on the posts -- but doing it this way makes it look as if they're paying attention to the conversations of passersby.

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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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Baring all

Tom Ryan*, my first landscape architecture mentor, and I have discussed the desirability of specifying that the trees and shrubs we design into a site be planted bare root whenever possible. As long as the roots can be kept moist — something now entirely possible with the use of hydrogels — most nursery-grown plants fare better, are more apt to be planted in a way that promotes their future health, and are less expensive than B&B plants. And we all know that healthier plants mean more long-lived designs….

Nina Bassuk and the Urban Horticulture Institute at Cornell have put up on the web an outstanding illustrated tutorial on how to plant shrubs and trees bare root.

One of the challenges for landscape architects is to get more nurseries to offer bare-root plants for sale. Currently, balled-and-burlapped and container-grown are the most available kinds of woody plants in the nursery-to-contractor trade. Like any business, nurseries respond to demand.

Like any business, nurseries respond to demand. Years ago, I was having a casual chat with the president of a local nursery and garden center, and asking why plant selections were limited to a number of fairly standard species and cultivars (I had recently assembled a plant list that specified some more unusual species than his large nursery carried). He told me that if his nursery responded to demand; without greater demand for more variety, his business stuck with the standard choices. If more contractors were to bring him more complex lists, his nursery would be happy to accommodate them. It’s a bit of a chicken and egg argument — but essentially it means that continued and persistent demand will get results.

If landscape architects, through our planting choices and plant specifications, possess the ability to influence nursery offerings, then why shouldn’t we also be able to influence the method with which those offerings are packaged? With a greater understanding of the benefits of bare-root plants, perhaps more of us will start to specify bare-root plants, and so create the demand for nurseries to meet. It’s an idea worth exploring.

If you have had experience specifying bare-root plants for a project, we’d love it if you would write in and tell us about it.

Chionanthus retusus, Swan Point Cemetery

*This September Tom will be named a Fellow of the American Society of Landscape Architects — a great honor for any landscape architect, and one that he fully deserves.

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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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Extractive landscape

I was thinking today about the way that our culture is largely extractive — we pull apart individual elements out of natural materials, and use those elements for specialized purposes (oil from the ground to power the internal combustion engine, vitamins from food to recombine into other foods, etc.). We are now seeing the limits of some of that extractive behavior, and are beginning to explore how to work within the full complexity of natural systems to achieve our energy, food, and shelter goals. To do so requires a better understanding of the natural systems around us, so we can see how human activity might fit in to them in a more sustainable way.

Our extractive tendencies show up in the garden, too. As Toby mentioned, he and I have been talking about monocultural landscapes, as opposed to the more complex landscapes often found in nature. I was making a point about some of the more beautiful designed landscapes I’d been seeing images of recently: residences with extensive knot gardens, a spot of topiary, and layered hedges. Those places garner oohs and ahs — from me as much as anyone else — but after I’ve seen a few images, I’m done. I realize that the hedges help compose each shot, and once I’ve seen the graphic composition, I’m often left with not much to look at.

The idea of facing down a 5′ high yew hedge with a 3′ high barberry hedge, and facing the barberry hedge with a foot-high Japanese holly hedge is cool; covering up the shrubs’ bare legs gives a full, buttressed look to the geometric lines edging a space.

Nice use of hedging varieties -- use with restraint

I’m as inclined to do it as anyone else (in moderation, I hope).

Somehow, though, making an entire landscape this way feels like clobbering a property into submission. Once I’ve seen the ‘rooms’ all these hedge walls make, I want to see a party of plants inside those walls. It makes sense to form space that allows free human activity to take place in it, and done well, it’s completely great (see Russell Page’s work). It also — at times, and perhaps in addition to this kind of hedge planting, if not in place of it — makes sense to design plantings that express a more organic understanding of the natural world. Why is it that formal hedges telegraph a sense of sophistication in photographs, when designing communities of plants requires greater effort, knowledge, and skill? Replicating or designing a complex system is a far more sophisticated exercise in my mind than setting out geometric patterns of the same plant, as fun as doing that is.

Perhaps I’m just crabby on this topic because I’ve done a great deal of hedge shearing in my time, and it’s strenuous, back-breaking work, and I’m little inclined to design a place requiring that sort of ongoing maintenance monotony.

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Air spade work redux

If you have read the last post but are new to this blog you might take a look at this link; it’s my Lawn and Landscape article on the bare-root transplant workshop conducted last summer by arborists Mike Furgal (who developed the method of transplanting specimen trees bare-root, using an air spade) and Matt Foti (who hosted the workshop and has gone on to use the bare-root air spade technique on every transplant project he can).

The article describes the workshop’s successful transplanting of several trees on a hot August day, and lays out some of the nuts and bolts of how the work is done. Mike and Matt’s workshop charged up every one of the 100 or so attendees. As a result, many Massachusetts arborists and contractors are turning to the air spade to save and transplant specimen trees. I hope that the previous post (“Air Spade in Action”) helps to expand our understanding of some additional uses of this tool.

(And no, I am in no way affiliated with the company that manufactures either the Air Spade or the Air Knife, or any other kind of tool.)

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Air tool in action

This past winter I developed plans for a couple of areas on the property belonging to my longest-standing and wonderfully enthusiastic clients, L. and A. on the North Shore. They have a lovely place on a rocky cliff overlooking Nahant Bay, and they enjoy making it even more beautiful and comfortable each year. They are both artists, and both appreciate art in two and three dimensions: L. gardens and sculpts; A. is a talented photographer.

L. and A. had asked me to figure out how to screen out views of two neighbors from their house, and to develop plans in the two areas that would work with the extensive mature plantings already in place. I drew up plans that would bring a few new plants in, as well as reuse a number of plants already onsite. L. and A. liked the ideas, and we scheduled a date to move ahead.

Leahy Landscaping of Lynn carried out the work of digging and moving the plants; the crew, led by Anibal Marita, was excellent. At my request, and under the supervision of Marc Bolcome, Leahy’s arborist, they used a compressed-air tool on the project; we were working in a heavily planted area and I wanted to disturb or lose as few roots as possible.

The plan: Remove a 32′ long, 7′ high holly (Ilex ‘China Girl’) hedge from the edge of a residential drive court, reusing some of the plants for screening at the front property line, and install a collection of transplanted shrubs, a new Japanese maple, and some low Green Wave yews where the holly had been. Transplant most of the hollies to provide a 22′ long screen at the front property line, and use the rest at another location onsite.

Proposed methods: Hand-dig the holly. To avoid further stressing the three aging red pines under which some of the hollies were to be transplanted, excavate the transplant site with an air tool. Hand-dig the rest of the plants.

Actual methods: Hand-dug the holly, then blew out the root balls to loosen the nursery soil at their cores. Discovered that the wire baskets had not been removed at the original planting, removed those, and loosened the remaining soil, leaving roots intact. Removing the soil allowed the plants to fit in shallower-depth holes, which was helpful on a site with a lot of existing tree roots and drainage pipes. Removing the wire baskets will allow the hollies’ roots (and crowns) to grow unimpeded in their new locations.

Excavated under the pines with the air tool, and removed existing shrubs there also with the air tool, leaving all roots, including masses of feeder roots, intact.

Unwrapped the Japanese maple root ball, removed the wire basket and burlap, and removed/loosened the soil with the air tool.

Removing a girdling root from the Japanese maple. Note the root-ball soil line, four inches up the tree's trunk from the base of the trunk flare.

With a mini-claw mattock, pulled soil away from the trunk flare; soil had been piled 4″ up the trunk, concealing a girdling root and the flare itself. Marc Bolcome chiseled away the girdling root and made sure the flare was correctly exposed before laborers backfilled and watered in the root ball.

Removed the red clay soil encasing the nursery root ball of a rhododendron that had been planted onsite several years ago, but that had struggled for those years.

Breaking up the clay soil in the root ball of a rhododendron that had been planted under these pines a few years back.

With the concrete-like soil mostly gone, the plant should finally have a chance to spend its energy growing, rather than trying to break through that clay cast.

Cleared ground cover by hand in front of a row of mature Taxus trees,

Holes for holly transplants were dug by air tool, to minimize disturbance to the roots of the treeform yew hedge behind the plywood.

then excavated transplant holes with the air tool — again, to keep from disturbing roots of the existing yews — and transplanted more of the holly here.

The original plan, which also included the planting of six large clump bamboos and the moving of several broadleaf evergreen and herbaceous plants, was scheduled to take perhaps two days.

The hollies changed everything, though. They were enormous: planted eight or nine years ago at 3′ on center, they opened out to seven to eight feet in width.

One holly, trussed for moving. Ten of these plants had been placed on 3' centers to make a hedge; when freed from the hedge, each one opened out to cover at least seven feet in breadth.

There was no way we could fit them all where we had intended; they would have taken up more than seventy feet if we had placed them side by side!

Hand-dug holly that has been bare-rooted being prepared for transplant. Notice the clumps of hard, heavy soil from its original root ball lying around it; the wire basket is lying off to the left.

The trussed holly, now untied and moved to the planting bed, is at the back right of the photo. Liberated from the crush of a too-tight hedge planting, it has opened out to cover almost nine feet of fence.

It took a while to figure out where to put them, and then more time preparing those new locations to receive them. We ended up placing them — ten from the hedge, plus a shorter male plant — at various points around the property’s edge, where they do a magnificent job of screening out the neighbors.

We also used the air tool to excavate under some mature and very stressed red pines. Removing the pines wasn’t an option, so to minimize any added stress, we blew out a planting trench between the pine trunks and the fence, exposing but not disturbing the pines’ roots. We roughed up the bamboo roots, taken from their five- and seven-gallon pots, and set them in the trench before backfilling and watering the area.

All told, accomplishing the work took a full three days.

Lessons learned:

1. An compressed-air tool is a great tool for any kind of planting work. We tested its capabilities, and found it invaluable for working under trees, for bare-rooting new plants, for excavating existing shrubs, and for removing that dreadful red clay soil from the 4′ rhododendron. We used it to investigate suspicious root issues — that concrete-like slug encasing the rhody’s root mass, the hollies’ wire baskets, the Japanese maple’s buried root flare and girdling root — and when it wasn’t being used on the transplanting operation, we used it to give a little breathing room to the root flare of a river birch planted on site a few years ago.

On this particular site, which has been intensively gardened for decades, the soil is beautifully dark and rock-free. The air tool had no difficulty blowing it out of planting holes. Even with a rockier soil, an air tool has enough pressure (90 psig in this case) that bare-rooting shrubs takes a relatively short time. A laborer team can generally dig a 4-5′ broadleaf evergreen shrub in minutes. An air tool can do it as quickly or in a few more minutes, depending on soil type — but the amount of root mass saved makes the air tool by far the preferred method, horticulturally.

2. Plywood screens work beautifully to confine the overspray of soil from the spading site. For bare-rooting the already-dug hollies, the landscapers figured out that they could lift each plant into the back of their high-sided truck and spade off the root soil there, which kept the soil contained and the site clean.

3. At a minimum, workers using the air tool or helping with the bare-rooting should wear goggles and a face mask; very fine particles of soil spray everywhere at high pressure, and eyes and lungs should be protected. In rocky or sandy soil, the hazard is greater, and long sleeves and protective visored helmets are a good idea. The compressor is loud, too — ear protection should be used as well.

4. Never plant China Girl hollies that close together. They have a lush and luxuriant round form, and are determined to grow to that form (shrubs will push to grow into their particular habits — with some, you can push back by hedging them, but it makes sense to pick a variety whose natural habit lends itself to hedge form). Ten hollies had been planted at 3\’ o.c. to make a hedge; when removed from hedge configuration, the plants spread to between seven and nine feet in breadth. These plants now make a contribution to the landscape that they couldn’t in hedge form. L. couldn’t remember if the original plan, done by another LA, had called for China Girls or for some other holly, and wondered if the contractor might have substituted China Girls for something else. We’ll never know — but we’ll know what to avoid in future.

5. It made a ton of sense to excavate the bamboo’s planting trench with compressed air; with air, the pines’ roots remained intact and we could spread the bamboo roots out easily within the broader rooting area we had exposed.

Conclusion: The planting techniques were first-rate, the plants looked happy, the place looked great. L. and A. are delighted with the results (I know I’ve succeeded when I’ve pleased their artists’ eyes), and Leahy is moving on to do other air tool projects, knowing how well the technique works in a number of different situations. Now we’ll all be watching to see how everything grows; I’m betting they will all thrive.

Company: Leahy Landscaping of Lynn, MA
Leahy Project Manager: Aisha Lord
Leahy Arborist: Marc Bolcome, MCA
Leahy Foreman: Anibal Marita

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Landscape architects?

Yes, yes, I know. I’ve been posting on shrub pruning and management, something most often left to the gardeners. And I’m a landscape architect — people think of us as the ones to go to for design. But how can you design a place without really knowing the elements in your palette, including the most complex ones?

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VFW Parkway

I drove in to Boston yesterday along the DCR’s VFW Parkway, a slightly winding, mildly rolling roadway lined on both sides and on the median with rows of mature pin oaks.  

Boston's VFW Parkway

My eye reflexively looks out for hazard limbs whenever I drive the parkway, and yesterday I saw a couple of doozies:  one 20-30′ long limb that hung from its tree with just the wrong degree of droop, and one 15-20′ long limb that was attached to its trunk at the correct angle, but it was riddled with the ochre fruiting bodies of fungi that have colonized the long-dead wood.

 

That, and the repeating ranks of thick trunk/columns marching along the roadsides, got me thinking about decay and renewal.  In England, it’s not unusual to see an established site design, its trees having matured and expressing the gravitas of site and species, with a second, subordinate planting of juvenile trees that echoes the layout of the mature plants.  Those guys are thinking ahead:  when the mature planting finally fails, the second string of trees will already be established, and the loss of the elders won’t be so devastating.  I saw a wonderful example of this technique at Wayland’s Smithy in Wiltshire, near the Uffington White Horse.

Wayland’s Smithy is a chambered long barrow –that is, a kind of neolithic burial mound — perched on top of one of the chalk downs that runs the length of Wiltshire County.  It is surrounded by a ring of mature beech trees, visible in this photo:

Wayland's Smithy and beeches

 

 

What you can’t see in the photo is the wider ring of beech saplings, planted some time in the 90s, that will take over the majestic role now held by the mature trees.

This approach makes a lot of sense to me.  The Parkway pin oaks are emblematic of the Parkway, and so far still stand — but when they start to go, what will take their place?  I’m all for getting a new planting of something going.

Over on Cambridge’s Memorial Drive, the city arborist has begun to plant in new London plane trees, to take over when the giant and iconic London planes finally succumb to anthracnose.

(That leads to the question of if it’s wise to replace specimens of a pathogen-infected tree with smaller specimens susceptible to the same pathogens, but that’s fodder for another post….)

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