Archive for January, 2011

Wow.  We had some sunshine this weekend.  Can spring be too far off?  Before we know it, it will be time to start thinking about new plantings.  Is tree planting in your future?

You don’t need me to tell you that trees are important in public spaces.  Their benefits are pretty obvious.   But too often we think we can dig a hole, drop in a tree, and enjoy the shade for years to come.  A walk downtown reveals that trees have a tough time in an urban environment.  Stumps and empty tree wells tell the truth.  If we want the trees in our public spaces to look good after the ribbon-cutting, we need to be more aware of what trees need to survive.  That’s why I asked arborist Jeffrey Ling to talk about what it takes to create and maintain a healthy environment for trees.

Tree in a planter at the United Bank Plaza in Charleston, WV.


I first “met” Jeff in a LinkedIn discussion group.  I had been kicking around an idea to create an en pleine air studio for a local museum in a grove of tightly spaced trees.  I was concerned about overcrowding, so I posted a question about it in the discussion group.  Jeff’s responses so impressed me that I knew at some point I should pass along his thoughts.  Yeah, it’s a little technical, but you guys can handle it.  It’s stuff that people who are interested in public spaces need to know.

Here are Jeff’s thoughts…

Nearly every urban site has trees as a part of the design.  Trees provide form and function for a location.  They can be an inhibitor for visual trespass, a blocker of unwanted vistas, and produce valuable shade along with aesthetic interest.  As we all know, trees are a contributor to the overall statement and value of the public space.

What sets trees apart from all other plant selections is the wood.  Trees are unique in this regard.  It is the wood which produces the opportunities and risks for tree planting and tree longevity on a cultured site.

Above the ground, the wood is both descriptive of the species and directive of its character.  Wood is ‘tree engineering’.  Its genetic predetermination is the template to build the organism, yet trees are responsive growers and the shape, texture and plant vigor will be altered by orientation, competition and site management (or mismanagement).

Wood under the ground is even more critical for growth and support.  It is here where we can fall short.  There is no greater disregard for a tree’s potential than when the design places a tree in a space which can not accommodate the needed root zone development.  A general rule is 54 cubic feet of root zone per inch of trunk caliper.  Projecting this out; to grow an 18-inch shade tree one must prescribe a 1,000 cubic foot root zone.  Root zone volume is the first and primary variable for tree size and longevity.

Soil temperature is another constrictor to tree growth and size.  We know that urban landscapes are hotter than suburban or woodland sites.  As soil temperatures rise root function diminishes, and stresses, especially drought stress, increase.  William Graves of Iowa State University reports that when urban soil temperatures are over 90oF, tissue damage follows.

Finally, there’s the issue of water. Nearly all negative effects on urban trees are in one way or another based on water deficiency. While there are drought-tolerant species, in the end, it is a site, not a species issue.

As one who has worked on scores (maybe hundreds) of legacy and historical trees, let me strongly recommend that every designer have an arborist on call who can first assess the condition of existing trees on a given site, both in structure and entropy.  The arborist, as a specialist, can assist the designer in site directed issues with regard to tree growth.  It is a liaison which can produce greater value for the client.

Jeffrey Ling is a registered consulting arborist practicing out of Fort Wayne, Indiana and is the President of Arborwise, Ltd.  Learn more about Jeff and his company at

Sunset on the Blue Ridge Parkway.

Last fall my wife and I enjoyed a weekend getaway at a cabin on the Blue Ridge Parkway and one evening we decided to chase a sunset in hopes of a dramatic photo.  As the sun began to dip towards the horizon, we found an overlook with a promising view.  We chatted with some hikers just coming off a trail, then settled on the hillside and waited for the sun to color the sky.

There were a handful of other people with the same idea, and before long we had started a conversation with another couple.  Turns out they were locals, both professors at nearby Radford University.  As the sun continued to set, we talked about cameras, West Virginia and even learned how our new friends from Virginia had met.  I didn’t realize it at the time, but our casual conversation was the result of a phenomenon known as triangulation.

According to William “Holly” Whyte, triangulation is the process by which some external stimulus provides a linkage between people and prompts strangers to talk to one another as if they knew each other.

In our case, the sunset served as the external stimulus, giving us something in common to talk about.  In public spaces, many things can serve as the external stimulus.  It could be a view of something outside the public space such as a sunset or another irresistible dramatic view.  It could be a water feature or a sculpture.  It could even be other people or an event, maybe a street performer or a bluegrass band.

Yes, it’s common sense.  Maybe too common.  We are often impressed by the big, dramatic answers, yet more often what is really effective is a series of smaller, not-so-dramatic ideas that work together much like seemingly random threads work together to create a magnificent tapestry.

Imagine:  You go to the public plaza and discover a new sculpture.  As you try to figure out what it represents, someone asks you what you think about it.  Even if you admit that you know nothing about art, you will likely have a pleasant exchange with a new acquaintance, which you will now forever associate with the public plaza.

Features in a public space are more than just features, they can also serve to bring people together.  Knowing this should influence the placement and configuration of features so that opportunities for socialization may be maximized.


Are you a rational, logical thinker or do you operate on gut instinct?

Consider your first visit to an unfamiliar urban plaza.  You need to know if it’s safe.  The rational, logical thinker might contact the local police and ask about the plaza.  Maybe take a look at statistics, discerning which times of the day are safer than others.  He might inquire of the local shop owners, get the streetwise perspective.  After gathering all the information, he can then make a rational, logical decision regarding the safety of the plaza.

Anybody ever do that?

Of course not.  We might not even consciously consider safety when visiting that unfamiliar public space.  Upon arrival, however, our subconscious will kick in and we will scope out the space, look for scary people, hidden corners, and escape routes.  We will analyze the park’s image, determine if it’s well-maintained, and look for amenities or something interesting to do.  Then we will weigh all the positives and potential benefits against the perceived risks.  Then we will make a decision.  And all of this happens in the blink of an eye.  (It’s a concept Malcolm Gladwell discusses in his entertaining and very interesting book, Blink, which I highly recommend.)

Consider the garden gate.  If you were on a private estate, touring the gardens, the discovery of such a passageway might be intriguing.  There’s a mystery about what’s on the other side.  In the right setting, the narrow gate is an excellent entrance to another space.

In an urban or public setting, our blink evaluation would likely inhibit us from entering.  The question of what’s on the other side — or if we would even be welcome — would probably be enough to keep us out.  Of course you would not really expect to find a garden gate as an entrance to an urban public space.

So if the narrow entrance can be inhibiting, can we assume that the broad, easy access is better in the public setting?


First, it enables us to perform our blink evaluation much more easily.  This alone is going to give us a good feeling.

Then there’s the idea that there is no gate at all, either physically or psychologically.  With everything open, the space will feel more inviting.

The broad entrance can be made even more inviting if we can provide a transition zone, where we can stop and consider our options without actually committing to entering the space.  Maybe just a wide area next to the sidewalk where we can stop, look in, and think about it.  Being able to do that is another little bit of psychology in gradually drawing the visitor into the space.  Low, easy steps can also be a transition, causing people to linger, one foot on, one foot off.

Access to Pullman Square in Huntington is broad, easy, and inviting.

Now of course, the broad, easy access is only part of the equation.  If the other elements aren’t there, we’re not likely to cross the threshold.  But if we don’t have the easy access, the odds are against attracting many visitors.  There’s a lot of psychology in play.  The more we understand that, the more successful our public spaces can be.