February 8, 2017

Washington Square Park Self Guided Winter Tree Walk

On a very cold Saturday morning last December, Kaslin Daniels led an intrepid group of tree enthusiasts on a winter tree identification walk in Washington Square Park. Kaslin is a NYC Parks gardener and the lead gardener at WSP. We met beneath the centuries old English elm in the northwest corner of the park. Kaslin started of the workshop with a short lesson in what she called "tree detective work". To gather clues, we were directed to consider the growing habit or form, the bark, the twig (and its buds), and any persisting fruit or leaves (for the latter, oaks are a good example). Kaslin had branch and twig samples that she used to illustrate her lesson. As we walked she introduced more detailed terminology as relevant to the species we were examining. Once she concluded her introductory remarks we set off and below I outline the route.

1. English elm - Ulmus procera
This 300+ year old elm is perhaps the most famous tree in the park! Elms are a vase shaped species. The English elm has fuzzy buds. From this tree we walked east to an even older tree (species).

2. Dawn redwood - Metasequoia glyptostroboides
This species has an excurrent or central leader. The dawn redwood and bald cypress look very similar. One way to distinguish between the two is by looking at the leaf arrangement. Bald cypresses leaves are arranged alternately on the step. A mnemonic is ABC meaning alternative bald cypress. From there we walked east and looked south unto the lawn.

3. London plane tree - Platanus x acerifolia
I think this particular tree is actually an American sycamore (Platanus occidentalis) because of the white-toned camouflage of the bark. London plane trees tend to have yellow or green toned camouflage patterning. This tree is listed as American sycamore on the WSP Eco Map. I will confirm with leaf and seedball comparisons. Read more about the differences between these two species here. From the plane tree we looked at two small trees growing adjacent to the tot playground.

4. Saucer magnolia - Magnolia x soulangeana
A participant was curious about the crape myrtle so we looked at that tree before spending time at the magnolia. One of the identifying features of the saucer magnolia is its fuzzy terminal bud. We moved off the path unto the lawn just west of the fountain for a closer look at a catalpa and a pagoda tree.

5. Northern catalpa - Catalpa speciosa
This catalpa growing across from the tot playground is one of two Northern catalpas in the park. The other one is just slightly east of the Holley bust. A defining feature of the catalpa is whorled arrangement of the terminal and lateral/axillary bud.

6. Japanese pagoda tree - Styphnolobium japonica
Most twigs are a shade of brown but the twigs of the pagoda tree are green. (Note: a twig is previous year growth while stem is current year growth. Stems tend to be green.) Another characteristic of the species is the presence of a pseudo-terminal bud. The pseudo bud mimics a terminal bud but is in fact a lateral bud. Look for a leaf scar. Learn more about bud types here. Our next large statured tree was across the central path in the lawn across from the comfort station.

7. Ginkgo - Ginkgo biloba
Like the dawn redwood, the ginkgo is a prehistoric tree. In leaf, the species' leaves are distinctive -- they are two lobed and fan shaped. In the winter season, look for vertical furrows in the park and spurs on the twigs. Just south of the ginkgo growing in the same lawn are Japanese cherries and a red oak.

8. Japanese cherry - Prunus serrulata
There are two groves of cherries at the Thompson entrance to the park. The showy flowers of the northernmost grove make me think that the cultivar is 'Kwanzan'. The flowers of the southernmost trees are more delicate and remind me of the Yoshino variety. Regardless of season, one defining feature of the Japanese cherry is the prominent lenticels on the bark which are arranged in horizontal rows. A lenticel is a gas exchange pore.

9. Red oak - Quercus rubra
Did you know that the bark of the red oak has a "ski track" pattern? A red oak's bark changes with age so be mindful of this variation. If you are tall enough or a branch is low enough, look for a clustered terminal bud which means that the terminal bud is surrounded by several lateral/axillary buds. Curious about variability in bark, twig (and bud), and fruit? Read here. Our next two trees have genus names beginning with the letter "L".

10. Tulip tree or tulip poplar - Liriodendron tulipifera
The tulip tree is one my favorite tree species. Imagine a lush canopy of vibrant green leaves generously sprinkled with lush tulip flowers. In late fall and winter you might see the base of the seed head persisting on the tree. The seedpods are held upright on the twig. Also look for duck bill shaped buds.

11. Sweetgum - Liquidambar styraciflua
The sweetgum has persistent seedpods, too. The balls are spiky. Another element to look for is corky twigs. We were also shown red (Acer rubrum) and sugar (A. saccharum) maples twigs.

At this point, Kaslin presented the option to conclude the workshop or to see additional trees. About half of the group peeled off the tour. The temperature had dropped and we were all uncomfortably cold. My camera battery had completely drained and my pen ink had frozen. I could not take more notes or photographs. The remaining participants walked further east then north and were shown black locust (Robinia pseudoacacia), hawthorn (Crataegus spp.), and honey locust. We did not stop at the white ash (Fraxinus americana), golden rain tree (Koelreuteria paniculata), or little leaf linden (Tilia cordita).

12. Honey locust - Gleditsia tricanthos
The honey locust we looked at is a street tree on the NW corner of Waverly and University Place. You can find honey locust growing in the sidewalk on the western edge of the park. At the Washington Place entrance you will find a honey locust or two growing in the park.

I'd like to tag the tree stops on a Google map so you can have a mobile map for your next walkabout in Washington Square Park. Stay tuned!

This workshop was co-sponsored by Washington Square Park Conservancy and Washington Square Park (WSP) Eco Projects.

February 1, 2017

Book Review - Urban Forests by Jill Jonnes

Urban Forests, by Jill Jonnes. Cover image via Penguin Random House.

Jill Jonnes is the author of six books including the subject of this book review, Urban Forests: A Natural History of Trees and People in the American Cityscape. The city is both the lens and the landscape is all Jonnes' books. However, in Urban Forests, nature, in the form of urban trees, is the primary focus. I came to know of Jill Jonnes' interest in urban forests through her essay titled "What is a Tree Worth?" published in the Winter 2011 issue of the Wilson Quarterly. Jonnes was a public policy scholar at the Woodrow Wilson Center in 2011. After reading her essay, I asked her to review a draft of my article manuscript which she did kindly. That manuscript was eventually published as "Mainstreaming the environmental street trees" in 2013 in Urban Forestry & Urban Greening.

Urban Forests is an excellent example of the use of multiple sources of evidence to craft and support an argument. If you only look at the Acknowledgements and Notes you will see that Jonnes interviewed the urban forestry community in all the cities featured in the book. As well, she traveled to these cities for first hand experience with the landscapes she describes. Furthermore she was a participant observer in her city of Baltimore where she founded the Baltimore Tree Trust. In addition to these rich sources, Jonnes relied on historic and contemporary newspaper articles, diaries, field guides, trade magazines, and academic publications to produce a biography of urban trees in the U.S.

Jonnes is not the first person to write about urban trees in the U.S. There is Thomas Campanella's 2005 Republic of Shade: New England and the American Elm and Evelyn Herwitz’s 2001 Trees at Risk: Reclaiming an Urban Forest. The article “From Nature to Nurture: The History of Sacramento's Urban Forest” by E. Gregory McPherson and Nina Luttinger was published in 1998 in the Journal of Arboriculture. In his 1993 Street Trees: A Manual for Municipalities, Richard D. Schein devotes a chapter to street tree planting from the colonial era to the 1970s in the Eastern U.S. The evolution of tree planting in European and American cities is the subject of Henry Lawrence's 2006 book, City Trees: A Historical Geography from the Renaissance through the Nineteenth Century. The limits of these books (and articles) are in their focus on a single species, or a single town or region, or a truncated timeline. Jill Jonnes' Urban Forests considers the arch of multiple tree species in major U.S. cities to the present day.

Each chapter excluding the Introduction and the Afterword is the story of a tree species or two, or of a type of tree (ex: memorial trees), or of a tree advocate or three, or a tree disaster (ex: Dutch elm disease), or tree benefits. Some chapters include several of these elements. I won't list all the chapter titles here, and as I finished each chapter I said to myself, "This one is my favorite," so I can't share "my favorites" but I will share a few that resonated strongly with me. (The chapter titles are wonderfully literary!) Chapter One: "So Great a Botanical Curiosity" and "The Celestial Tree": Introducing the Ginkgo and the Ailanthus. The ginkgo is one of my favorite trees. Chapter Five: "Washington Would One Day Be Famous for Its Flowering Cherry Trees": Eliza Scidmore and David Fairchild. Cherry blossom season along the Potomac River in DC will meet your expectations. And typically you read stories about men's roles in urban forestry so it was refreshing to learn about a woman in this field. Chapters Twelve to Fourteen are about the development of urban forestry science and its strategic insertion into public policy. I wrote my dissertation about the changing "sets ofideas and prescriptions" (how Eileen Crist defines discourse) that govern the role of urban trees. I found that in the policy arena, urban trees had transitioned from primarily a beautification object to an environmental services tool. In combination, the chapters reveal that different benefits have been identified and made relevant over time, but consistently it is the emotional connection, which is so stark during times of massive tree loss, that binds us to our trees. Do you recall Michael Pollan's argument in the The Botany of Desire, that plants shape us? Our affinity for and efforts to understand, manage, and preserve trees have given rise to many institutions -- the US Forest Service, municipal forestry departments, various nonprofits, botanical gardens, arboricultural companies, and more.

I recommend this book. Nonfiction fans and historians will enjoy it. If you prefer novels, you will find Jonnes' writing style appealing. Policy makers should read this book, too. The quote at the end of the book should be regarded seriously when strategizing about improving environmental quality:
The more climate scientists study how best to stave off further warming of our planet, the more they understand the importance of trees and forests. 'Every time I hear about a government program that is going to spend billions of dollars on some carbon capture and storage program, I just laugh and think, what is wrong with a tree?" said Neil Sizer, president of the Rainforest Alliance. 'All you have to do is look out the window, and the answer is there.' 
Mr. Sizer was referring to a real, not artificial, trees. Real trees have the added value of co-benefits.

I'd like to conclude with this thought. The tree species featured in this book are among our most popular urban trees. Many of them are not native to North America but are intimately tied to the identity of our cities. Consider the role of the Japanese flowering cherry in our capital city of Washington, DC.

January 20, 2017

Songbirds in NYU Superblocks

Image: Washington Square Village and Silver Towers Complex by Angus Wilson (source)

I am steeped in bird data and migration ecology as I draft the annual report for the research permit Washington Square Park Eco Projects received to conduct a wildlife survey in the park. As soon as the report has been submitted I will post it here. I shared a list of the birds we observed in Washington Square Park earlier on in the survey period. You can find birds elsewhere in the vicinity of the park. Angus Wilson, of the Linnaean Society of New York (I did not know there was a Linnaean Society or that there was a NY chapter), published a list of songbirds sighted in the two superblock residential complexes owned by New York University. It with his permission and that of LSNY that I repost his essay below.



The residential complex associated with the New York University campus includes several small areas of trees and ornamental plantings that attract a variety of songbirds during migration and in winter. The main areas are the Sasaki Garden inside the Washington Square Village complex, the LaGuardia Corner Community Garden and adjoining Time Landscape Garden that runs along the east side of LaGuardia Place between Bleecker Street and West Houston Street and the Silver Towers Oak Grove on Bleecker Street. Additional pockets of vegetation border the superblock hemmed by West 3rd Street, Mercer Street, West Houston Street and LaGuardia Place and are always worth checking especially after a migrant fall. A fenced lawn behind the University mail office is used by foraging sparrows and thrushes. Although this area lacks the observer coverage of other Manhattan parks, a good variety of species has been recorded in recent years and careful scrutiny will most likely add to this list. A female Wild Turkey frequented the area for several weeks back in 1997 and a dead Pied-billed Grebe provided a sad testament to the hazards of tall building to nocturnal migrants. The mixture of mature trees, including many native species, ground cover and water sources likely contributes to this diversity. Sadly, this entire area is threatened by the NYU 2031 expansion plans that will replace most of the gardens and border strips with additional tower buildings.


Fall is the optimal season for birding this area. Good numbers of White-throated Sparrows frequent the flowerbeds and are often joined by Song, Swamp and Chipping Sparrows. Dark-eyed Juncos may also be numerous. Lincoln and Fox Sparrow have occurred as rarities. The trees routinely attract Yellow-bellied Sapsuckers in the fall and winter, along with occasional Northern Flickers. The Sasaki Garden provides wintering habitat for Hermit Thrush, and in late fall, it's not unusual to encounter a dozen or more. Together with American Robins and Cedar Waxwings these attractive thrushes exploit the plantings of crabapple and cherry trees in the northern section. In flight years, the fruit of these trees has attracted Purple Finches. Additional migrants such as Blue-headed Vireo, Winter Wren, Brown Creeper, Ruby-crowned and Golden-crowned Kinglets and Eastern Towhee may also be observed.

In spring, small numbers of warblers pass through but can be easily overlooked in the foliage. These have included Cape May Warbler and Chestnut-sided Warbler. One or two Wood Thrush are recorded each year. Drinking water and cut fruit are put out on the ground in the Time Landscape Garden, attracting Blue Jays and Gray Catbirds and might be worth checking for uncommon visitors. The resident Rock Pigeons and Mourning Doves attract the attention of Red-tailed Hawks, presumably coming over from nearby Washington Square Park, and American Kestrel, Merlin and Peregrine have all been seen on occasion.

Other Considerations and Directions

This is a relatively safe area, due in large part to its proximity to the University, which provides round-the-clock patrols of the area. The Sasaki Garden is closed during the hours of darkness and receives a fair amount of foot traffic during the day from residents and building employees. Be mindful of the privacy of the folks whose apartments face onto the garden. Signs forbidding photography in the gardens have disappeared and it's not unusual to see NYU film students at work in the park areas, but common sense should apply. Access to the Community Garden and Time Landscape Garden is controlled but both areas can be viewed through the fence.

The area is easily reached by subway to either the West 4th Street (A B C D E F M) or Broadway/Lafayette Street (B D F M 6) subway stations, both of which are only a short walk away.

Image and essay by Angus Wilson of the Linnaean Society of New York. The original post, WASHINGTON SQUARE VILLAGE AND SILVER TOWERS COMPLEX, can be read at http://linnaeannewyork.org/birding-resources-rba/bird-wash-sq-vill_silver-towers.html.

January 10, 2017

Tree Architecture and Snow

Another title I considered for this post was _Tree Geometry and Snow_ after the chapter title "Tree Geometry and Apical Dominance" in The Trees in My Forest by Bernd Heinrich. I planned to reread this book this year. With the recent snowfall, I read all the chapters about the why and how of tree growth. The most instructive for this post was the chapter titled "Construction for Strength". Last Sunday, the morning after the city received five inches of snow (four more than predicted), my family and I walked to Washington Square Park to get some fresh air and to watch the chipping of our neighbors' discarded Christmas trees. In between snow play and tree mulching, I photographed snow on several of the coniferous evergreens and deciduous broadleaf trees and shrubs in the park.

Here is basic tree geometry: conifers, which tend to be evergreen or partially so, typically grow symmetrically and straight vertically. Deciduous trees, mostly broadleaved, tend to have more rounded shapes. Within these generalizations are variations depending on species and environment. For example, ash, maple, and poplar trees are more "upward-pointing" while birch trees are "bushier". White pine is shade intolerant and so grows quickly vertically to maximize access to sunlight but in an environment where it grows as a specimen tree or without competition, it tends to grow horizontally, branching out and not adhering to an apical dominance regime with a single leader branch.

Upward-pointing versus bushy growth is differently impacted by snow loads (or ice). A more vertical tree (trunk, branches, twigs) presents less surface area to snow and rain (or ice). Where the branch attaches the trunk, the shape is more like a V which means snow or rain flows towards the trunk-branch attachment which can support more weight than the tip of a branch or twig. Imagine a deciduous tree in leaf or recently leafed out caught in a snow or ice storm! Such a bushy aspect under snow or ice loading would likely lead to significant loss of limbs.

Image: Spruce (possibly Picea babies), photo by Sergei Dorokhovsky (source)

Evergreen conifers retain their leaves in winter and withstand snow loads. Their vertical and symmetrical geometry is that of a cone hence the name conifer. These trees are wider on the bottom and narrower on the top. The weight of snow causes the higher branches to droop unto the wider lower branches which can support the load. Think of how an umbrella sheds rain or how snow slides of a pitched roof.

Remember earlier I mentioned partially evergreen conifers? It turns about that white pine falls in this category. It "sheds half of its leaves each fall", the older ones closest to the trunk. Balsam firs and red spruces shed their leaves for between five and 10 years. Some conifers are deciduous such as the Dawn redwoods planted in Washington Square Park. There are broadleaf evergreens, too, like the hollies growing near the half-circle seating areas on the eastern side of Washington Square Park. You also may encounter some red oaks that cling to their leaves or red oak leaves that cling to their trees.

The more you learn about trees, the more fascinating they are in all seasons. Stay tuned for a self-guided winter walk through Washington Square Park.

December 15, 2016

Storm King Art Center - Family Field Trip

My first exposure to big sculpture was during a temp assignment at a construction firm in the East Bay (California). I was assigned to the human resources department and one of my tasks was to organize the art files of the firm's owner. Doing this work, I saw the large scale pieces of artists like Ann Hamilton, Richard Serra, and Andy Goldsworthy set in the expansive landscape of the Oliver Ranch. When I travelled to Seattle several years I visited Olympic Sculpture Park specifically to see Richard Serra's 'Wake' and was also treated to works by Alexander Calder and Mark di Suvero. I have lived in New York for the past seven years but didn't hear about Storm King Art Center until a couple of years ago. Two weekends ago, I visited the sculpture park with my family. The experience was well worth the long drive and cold and windy weather. We basked in the intermittent sun. We did not walk all 500 acres of the park. The route we took was recommended to us by the owner of the pop-up cafe. Follow in our footsteps in the South Fields.

Nam June Paik - Waiting for UFO, 1992 

Alexander Calder - Five Swords, 1976

Alyson Shotz - Mirror Fence, 2003

Dennis Oppenheim - Dead Furrow, 1967/2016

Roy Lichtenstein - Mermaid, 1994

Andy Goldsworthy  Storm King Wall, 1997-98

Another set of large scale elements in the landscape are the park's trees. Thick trunked mades line the drive near the 'Pyramidian' by Mark di Suvero (pictured above). Red oaks populate the uplands area near the visitor center. Moodna Creek is lined with birch, willow, and sycamore. Pin oaks line the drive near 'Storm King Wall' by Andy Goldsworthy.

Zhang Huan - Three Legged Buddha, 2007

I look forward to returning next season. I want to see the entire length of Storm King Wall; I want to see Maya Lin's 'Storm King Wave'; and then we did not explore the Meadows and North Woods. Storm King is a wonderful place for children. We did not hear any complaints about the inclement weather. The landscape's rhythmic qualities and never-ending seeming aspect were both exciting and restorative. If you get the opportunity to visit Storm King Art Center, take it.

December 8, 2016

Maps of NYC Street and Park Trees

Image: WSP Eco Map showing tree clusters and Minetta Creek

With the release of the NYC Street Tree Map by the Parks Department this fall, I wanted to plug the WSP Eco Map, a project of Washington Square Park Eco Projects, which shows the locations of the 200-plus trees growing in the almost 10-acre park. Washington Square Park is not the only city park with a map of its trees and natural resources, but it is rare among the New York City's 1900 parks and playgrounds.

Image: Tree Map of Tompkins Square Park (via Tompkins Trees)

When I began exploring a tree map for Washington Square, I met with Michael Natale, who surveyed all the trees in Tompkins Square Park and created, without external funding, the map you see above. The Tompkins Trees map is beautifully detailed. Carl Schurz Park also has a print map of its trees developed by its conservancy. In case you are unfamiliar with the park, Gracie Mansion sits at its northern tip. Download the Trees of Carl Schurz Park here.

Image: Central Park Entire: The Definitive Illustrated Folding Map (via Central Park Nature)

I own a copy of Central Park Entire: The Definitive Illustrated Folding Map by Edward Sibley Barnard and Ken Chaya. Barnard and Chaya independently researched, developed, and self-funded the map over a two year period. In addition to architecture and art, paths and trails, waterbodies, and rock formations, the Central Park map depicts all the park's nearly 20,000 trees. Learn about the mapping process in the Two Years of Mapping Central Park video or in this New York Times profile. The Central Park Conservancy has its own browser-based Tree Guide that can be filtered by species, general location, and attributes such as flowering and fall color.

Although the High Line does not have a formal tree map, you can use its monthly bloom lists to identify showy-flowering trees as well as shrubs and herbaceous perennials growing in the different garden zones in the park.

Image: Screenshot of Profile of Pugsley Creek Park, Bronx, NY on NAC's Nature Map 

The Natural Areas Conservancy which works with the NYC Parks Department to protect, as the name implies, the natural areas in the city's greenspace portfolio including wetlands and open water, launched its Nature Map this year. You won't find individual trees pinpointed on the map but you will get information on park size and percent landcover type. For example, Pugsley Creek Park in the Bronx is 83 acres of which 12 acres is forest, 4 is wetland, 17 is grassland, and 27 is open water.

I've heard that the Battery Park City Parks Conservancy (BPCPC) is geotagging all the plants and infrastructure components in its system. I look forward to exploring that map. In the meantime read the lists of plants, birds, and fish that inhabit the Battery City park system. Note that Battery Park City parks are owned by the Battery Park City Authority (BPCA) and jointly managed by the BPCA and the BPCPC.

Image: Playground of the Americas, Houston and Sixth Avenue

Researching this blog post I was surprised to discover that many of New York City's parks do not have a tree map, or if they do, the map is not locatable on the internet. It's a good feeling to know that two small downtown parks are among those that do (and the maps were not developed by conservancies). At 9.5 acres, Washington Square Park is a small park. According to City Parks Blog, the median and average U.S. city park are 5 acres and 54 acres, respectively. For a point of comparison, Central Park is 840 acres. For very small parks and playgrounds with a handful of trees, a map might be unnecessary. I profiled the trees in several such playgrounds in Greenwich Village for ioby's Recipes for Change blog series. Read the essays!

The Trees of the Playground of the Americas
The Trees of Minetta Playground
Trees of the Playground at Pier 25
The Trees of Evelyn’s Playground

Did I miss your tree map? If your NYC park (or playground) has a tree map in print or digital form and I did not mention it in this post, please let me know in a comment. Thank you.

P.S. I Quant NY used the city's 1995 and 2005 street tree census data to create Are You in One of NYC’s Treeiest Neighborhoods? (hat tip: Keith Allison/NYU). I profiled Jill Hubley's NYC Street Trees by Species map which was also created using the tree census data. By the way, the 2015 street tree census used a mapping methodology created by TreeKIT.

November 22, 2016

Fall Foliage Collected in Washington Square Park

My intent was to preserve the fall foliage I collected last week with glycerin and to use leaves as a teaching tool for Washington Square Park Eco Projects. Now the leaves may be too dry to preserve them in glycerin successful. There are still many leaves on many of the park's trees so I still have time to collect freshly fallen samples for preservation. I must hurry though has the parks department is cleaning up fallen leaves and winter weather has arrived suddenly with flurries and cold, fast moving winds. The preservation process seems straightforward. Prepare a 1:2 ratio of glycerin to water and pour the mixture in a shallow tray, spread the leaves in the solution, weigh down the leaves so they remain submerged for four days on average, remove the leaves from the solution and pat dry.

Here are my favorite resources:
Glycerin Leaves [Tinkerlab]
How to Preserve Fall Leaves and Branches with Glycerin [Today's Homeowner]
Preserving Leaves [Martha Stewart]

Have you preserved leaves? What method did you use?

The labeled image at the top of the post would also make a good learning tool but it cannot replace the experience of holding an actual leaf. Most of the trees are peaking in Washington Square Park so this is a good time to visit for fall foliage. If you can't make it to the park, enjoy its autumnal show through the photos below.

Washington Square Park, Fall 2016 Foliage, 11/12/16
Washington Square Park, Fall 2016 Foliage, 11/12/16

P.S. The species represented above are different from the ones whose leaves I gathered days after Hurricane Sandy in 2012. The leaf litter I observed in Washington Square Park after the superstorm was heavy on the oaks.