Photos: Dennis McGlade

“Are there lilac trees in the heart of town?” That’s love struck Freddy Eynsford-Hill’s rhetorical question in regard to the object of his desire, Ms. Eliza Doolittle, in the Lerner and Loewe song “On the street where you live,” from the show My Fair Lady.

If Eliza lived in Philadelphia instead of London, the non-rhetorical answer to Freddy would be “why yes, they grow on quite a few streets in Center City.”

Since the 1980s, the Philadelphia Horticultural Society has been selecting and planting street trees throughout the city. So have countless homeowners and block groups. The results are impressive as to both quantities of trees planted as well as their botanical diversity. The trees–Oaks, Maples, Bald Cypress, and Liquidambar from North America, Lindens and some more Maples from Europe and Eurasia, Sophoras, Cherries, Ginko, Tree Lilacs, and Zelkova from Asia–come from all over the temperate world of the northern hemisphere and they make the city a literal urban arboretum.

The amenity value of the street trees is enormous–they provide seasonal beauty through flowers, fruit, and foliage. They screen (at least when in leaf) the plethora of pedestrian architecture that lines too many of our streets, taming the visual chaos with a stately procession of visual calm in pleasantly modulated shades of green foliage. They shade and cool the streets in summer. Their foliage collects particulate pollution and releases oxygen into the air. They provide habitat for birds and insects and other fauna. They provide psychological respite from urban stresses by being a link to nature, catering to our most basic “biophillic” needs.

Over the years I have been observing the street trees in Philadelphia. The following is a sampling of my observations about these arboreal neighbors and the way some of my fellow Philadelphians interact with them.

A. Philodendron in Philadelphia
The root word “phil” is from the Greek word meaning “liking” or “love.” “Dendron” is from the Greek word meaning “of, or relating to, a tree or trees.” Can one love a tree too much? Do even hardy trees get chilly in the winter? Perhaps some of us think so.

Photos: Dennis McGlade

B. On the Other Hand: Bondage and Strict Discipline
Espalier is a French word for a tree training technique whereby a tree is grown flat against a wall. The branches are trained along the face of the wall with no branches allowed to grow out from the wall. It was used originally for more tender fruit trees to capitalize on the warm micro-climate provided by south facing walls that absorbed heat from the sun all day and blocked cold winds from the north. Perfectly hardy fruit trees were also trained this way to accelerate their fruiting by a few weeks ahead of the same trees growing in the open. Over the years, the technique has been done for purely ornamental reasons, using species other than just fruit trees. The espalier in this photo is a Blue Atlantic cedar that has been trained against the wall of this Center City town house for over 20 years.

Photo: Dennis McGlade

C. Please DO Fence Me In
When is a tree pit not a tree pit? When it is a garden. In this case a curbside garden made possible by fences that eliminate dog and people trafic. For tree pits “fences make good neighbors,” not withstanding Robert Frost’s reservations to the contrary.

Photo: Dennis McGlade

D. When Tree Pits Are Not Enough
Some neighbors cannot “contain their enthusiasm” and accessorize the tree pit with even more opportunities for horticultural display.

Photo: Dennis McGlade

E. For Everything There Is a Season
One of the often overlooked aesthetic dimensions of trees is the interception of snow on their branches in winter. With the right kind of snow the results are quite poetic, no less so for being so delicate, fragile, evanescent–the effect often disappearing within a very few hours after the event. This hawthorn in Cianfrani Park is bedecked with white flowers in mid spring, the visual effect being reminiscent of the snow resting on its branches the winter before.

Photo: Dennis McGlade

Photo: Dennis McGlade

F. And Now, For Something Completely Different
While there are proven and approved lists of suitable street tree species and cultivars for Philadelphia’s streets, local residents still like to experiment with unusual ones, like this specimen on Catherine Street–a native red cedar–Juniperus virginiana. I doubt if you will find this tree on any street tree list for Philadelphia, but it may prove to be a small scale evergreen conifer that is suitable for sunny and hot Philadelphia streets.

Photo: Dennis McGlade

G. Since When Is a Ginko a Broadleaved Evergreen Tree?
When it is a trellis festooned with English Ivy.

Photo: Dennis McGlade

H. When is A Tree Pit Not a Tree Pit?
When it is a Cana Lily pit or an Elephant Ear pit?

Photos: Dennis McGlade

I. Tight Shoes
Trees are biological systems in balance. The amount you get on top–the branches and the leaves–is balanced by the amount below that is not visible–the root mass. When I see this tree and look at the base of the trunk where the roots flare out and look so painfully squeezed between the curb and the sidewalk, I think of all the people I have known over the years who suffered for fashion–big feet in small but very chic shoes. Do trees feel pain?

Photo: Dennis McGlade

J. Big Trees, Small Pits
It is amazing how big some of our street trees can grow even from the tiniest pits. Healthy trees are living systems in balance with their environment. Running under sidewalks and street pavements, the roots of these trees far exceed the area of their original tree pit. The roots are probably located right at the interface of the compacted sub-grade soils and the more permeable and aerated gravel base directly beneath the pavements, where there is moisture and air. Contrary to popular belief, trees do not seem to need that much organic matter in the soil if they can get plenty of
root run and moisture in the mostly mineral substrate of our roads and sidewalks, along with sunlight to drive the photosynthetic process.

Photos: Dennis McGlade

K. Tragedy
Trees whose roots get out of the tree pit and under pavements can be prone to toppling. Tree pit design is arguably more important than tree selection in that a well designed tree pit will relieve the tree of any growth stresses associated with tiny pits–insufficient moisture or room to solidly anchor the trunk. Tree pits should be considered as part of the street and side walk infrastructure and room for them must be found within the limited real estate that must be shared by all the utilities also under the street and sidewalks.

Photo: Dennis McGlade

L. Transformations
When it all comes together–right tree in right pit–the city street is transformed. Philodendron Philadelphia indeed.

Photo: Dennis McGlade

Photo: Dennis McGlade

Photo: Dennis McGlade

Photo: Dennis McGlade