10 Questions About Planetrees - Jim Chatfield

London planetrees in Brooklyn, New York

SycamoreSycamore in Oberlin, Ohio.

Q1. - What is the difference between sycamore and London planetree?

A1. – Sycamore (Platanus occidentalis) is the American planetree, while London planetree (Platanusxacerifolia) is a hybrid with the Oriental planetree (Platanus orientalis). It is thought to have hybridized at Vauxhall Gardens in London where planetrees were collected from the respective native North America eastern Europe/western Asia ranges. The London planetree hybrid became very popular in London and in western Europe for its adaptability and pollution tolerance. It is overplanted in some community forests, resulting in lack of diversity.


London planetree in Brooklyn, New York.London planetree in Brooklyn, New York.

Q2. - Are there still other planetree species worldwide.? 

A2. - It was news to me that there are two additional planetrees in the United States,Platanus racemosain California, andPlatanus wrightiiin Arizona, New Mexico, and Mexico. In retrospect some of the planetrees I saw in past years in native canyon areas in New Mexico and in California were probably these other species, though I just assumed they were sycamores at the time. I did notice more star-like features of foliage and more slender stems, but this barely registered – until now, especially as I spend some time with various websites, and with “The Tree Book” by Michael Dirr and Keith Warren (2019). There is also another species,Platanus kerrii, native to Vietnam.

Q3. – How do you tell the difference between sycamore (American planetree) and London planetree?

Sycamore fruitsSycamore fruits, typically one per peduncle.

A3. – It can often be difficult, since after all, sycamore is also now hybridizing with London planetree and new cultivars of these hybrids continue to come on the market, but there are some helpful characteristics. First, the exfoliating bark that peels off planetrees, providing contrast (and messiness) tends to be whiter and has fewer khaki tans and greens on sycamores than on London planetrees.

Sycamore leafA sycamore leaf with large ears at the leaf base.

London planetree leaves with plant bug damageLondon planetree leaves. With plant bug damage.

Second, sycamore more generally has one fruit per fruit stalk (peduncle), while London planetree more commonly has two. Third, and this is one I think is at least somewhat reliable but not fool-proof: sycamores tend to have droopier ears at the base of the large leaves, while London planetrees seem to more often have the leaf blade flat across at the base. Don’t go to the bank with this third feature, but see if it fits and let me know. 

Q4- Is there some confusion regarding the common name of “sycamore”?

A4. – Yes. The first one I learned from a bit of googling: there is a a fig,Ficus sycamorus, the sycamore fig native to Africa and Lebanon, sometimes simply known as a sycamore, or sometimes spelled “sycomore”. It is referred to numerous times in the Bible, as in,  

Psalm 78:47: “He destroyed their vines with hail/and their sycamore-figs with sleet.”

A second example I learned while in Scotland and England this Autumn. They have London planes of course, especially as street trees, but they also have a plant they regularly call sycamore – and it is not the American planetree, as we commonly say. It is a maple! What we call sycamore maple,Acer pseudoplatanus. This is another reminder of how common names, rather than the Latin binomial, can result in confusion. The common and Latin name of this maple does relate to our name of American planetree/sycamore, as the leaves do look somewhat likePlatanus occidentalis.

Sycamore mapleSycamore maple, with flower cluster, at Dow Gardens in Michigan.

Sycamore mapleSycamore maple at Nate Ames place in Columbus.

Some giveaways that it is a maple, though, range from the winged fruits of maple, the opposite leaf arrangement of maple, and easy on my eyes as a plant pathologist, the fact that there is considerable maple tar spot disease on the sycamore maples we saw, which were many compared to sycamore maples found in North America. Sycamore maple is native from central Europe to Ukraine and was introduced to the British Isles in the 1500s.

Tar spot disease of sycamore maple in ScotlandMaple tar spot on sycamore maple (they just call them sycamores) in Scotland.

Q5. – So, what are some common diseases of planetrees?

Sycamore anthracnoseSycamore anthracnose with classic water-soaked blotching along leaf veins.

Sycamore anthracnoseThe effects of sycamore anthracnose in early Spring in upstate New York.

A5. – Most of us are familiar with sycamore anthracnose disease (fungal pathogen:Apiognomonia veneta) with the annual (some years more noticeable than others) leaf blight and twig dieback in Spring. The good news is that it rarely kills trees, though it seems like it early in the season. It is also good news that it is less prevalent on our London planetree street trees than on sycamore, thanks to thePlantanus orientalisparent. Keys for bad sycamore anthracnose years are cool, wet weather during leaf emergence, as the fungus overwintering on twigs has ideal ”environment conducive to disease” conditions. 

Sycamore anthracnoseLeaf blight and stem dieback from sycamore anthracnose in Marietta along a the Ohio River.

Sycamore anthracnoseGotta love those disease symptoms.

Powdery mildew is also quite common onPlatanus, with symptoms of leaf distortion, especially on new foliage, including leaves that emerge from buds in June after the first set of leaves may be slammed by anthracnose. This disease is primarily cosmetic and not serious relative to plant health. Both anthracnose and powdery mildew, though, contribute, along with normal shedding of bark and branch drop to an overall sense ofPlatanusas a “dirty tree”, especially so on sycamore.

Powdery mildew on planetreePowdery mildew on young planetree foliage.

More seriously, there are several stem diseases ofPlatanus, especially in the UK and Europe.Ceratocystis platanicauses a “canker stain” disease, especially on Oriental planetree, with greater resistance on American planetree and intermediate incidence on London planetree, all suggesting that the pathogen co-evolved withPlatanushere. It can be a killer.

The branch-damaging Massaria disease, caused by the fungusSplanchnonema platani, causing large branch lesions has resulted in several outbreaks onPlatanushybrids in Europe in the 21st century

Well, that’s it for now. Say tuned for,,, the Rest of the Story, with five morePlatanusqueries on a bygl-alert tomorrow, from cultural and horticultural notes to cultivars and more “name-en-culture”. 

Sycamore bark.Sycamore bark.

Till tomorrow:“Goodbye to buckeyes and white sycamores”from the song “Coal Tattoo” . 

Sycamore in Mt. GIlead, Ohio

Q6. – What are the key horticultural features of planetrees?

Sycamore at College of WoosterA large sycamore at the College of Wooster.

Looking up at a sycamoreI told you it was large - and tall. Jason Veil and Steve Shaffer visit COW from OSU.

A6. – Sycamore (Platanus occidentalis) and other planetrees love water, and you can see that along rivers. If you do not believe me, next winter, visit Clifton Gorge Nature Preserve in Greene County. Take the upper trail and look down toward the gorge and the Little Miami River. Beautiful sycamoreson either side, very defined when leaves are off the trees. They are not intolerant of reasonably dry sites, though. They grow fast and truly become large trees with age, both in size and spread: Michael Dirr & Keith Warren in “The Tree Book” cite 80 feet by 70 feet for London planetree (Platanusxacerifolia) and 75-100 feet tall for sycamore.

SycamoreSycamores are large trees.

Harvard glass flowers and leavesCheck out these glass flowers and leaves next time you visit Harvard's Peabody Museum. Over 4000 in toto.

They are “dirty” for horticulturists interested in mowing in the area, with fallen leaves and twigs from anthracnose, exfoliated bark, disintegrating seed-heads, and fallen branches. However. They are “the bone structure of the landscape” in winter and the mottled bark is sensational, the “everchanging vision of the everlasting view” as Carole King put it so well.

Planetree bark in Iowa yardPlanetree bark and leaves in Iowa yard. Good-sized "devil strip".

I suppose she was not really talking about planetrees, but who knows? Obviously planetrees do need some space and given certain conditions may cause sidewalk issues. Large maple-like leaves are impressive: we get a bunch of them in our yard each fall, though I am not sure where they come from; there are none nearby as far as I can tell, and they are big enough not to be carried by the merest wisp o’ wind.  

Q7. – What are some uses of planetrees?

A7. – Planetrees are widely used as street trees and for other ornamental uses. As large-canopy trees with fairly fast growth they have high i-Tree values for environmental services trees provide. Planetrees are used for timber and for biomass energy production.  

Tree walk at OSUObviously not a sign for a planetree. But it does give some ideas about I-Tree benefits. On OSU Campus.

Q8. – What are some cultivars of planetrees?

A8. – London planetrees are where the action is for planetree street trees and other horticultural uses. Some of the many you may want to investigate include:

‘Bloodgood’ for the attractive bark, anthracnose tolerance, and graceful form; one of the trees trialed in the Shade Tree Plot at Secret Arboretum.

‘Morton Circle’ Exclamation!TM is noted as the favorite by Dirr & Warren in “ The Tree Book”. Hybridized at the Chicago-area’s Morton Arboretum. They list its merits as its cold hardiness, straight trunks and narrowly pyramidal shape, and pubescence of spring leaves providing a somewhat silvery appearance. Morton touts its especially attractive exfoliating bark.

Others include ‘Liberty’, a National Arboretum selection “rivaling ‘Bloodgood” (Dirr & Warren); ‘Pyramidalis’ with a narrower form than most (abundant fruit production); and ‘Suttneri’ with variegations of cream, yellow, and green in the foliage and especially attractive exfoliating bark, exposing snow-white bark that Bill Hendricks of Klyn Nursery touts as rivaling white-barked birches.  

Q9. – What is the family for the genusPlatanus

Fossilized planetree from WIkipediaFossilized planetree fruit from the Cretaceous. From WIkipedia

A9. – This is an easy one. It is a member of the Platanaceae. And it is a mono-generic family. There are fossil relatives from the Lower Cretaceous Period, indicating that planetrees began to evolve fairly early in the development of flowering plants.  

Fossil planetreeFossilized planetree leaf from the Cretaceous. From WIkipedia.

Q10.- What are some cultural references to planetrees?

A10. – Let’s take a look at two. First, is the Pinchot Sycamore in Simsbury Connecticut. After my planetree bygl-alert yesterday, Richard Cowles of the Connecticut Agricultural Experiment Station, a new BYGL reader due to the tireless efforts of Joe Boggs, e-mailed that he lives 10 miles from said sycamore. It was measured in 2016 with an average canopy diameter of 121 feet, a trunk 18 feet around, a height of approximately 100 feet. 

Pinchot sycamore from WikipediaThe Pinchot Sycamore. From WIkipedia.

The Pinchot Sycamore is touted as the largest tree in Connecticut and tied at one time for second largest sycamore in the country, with the largest being astride a farm field near Jeromesville in Ashland County, Ohio. I use phrases such as “touted as” and “at one time” because storms happen and rot happens and new finds happen and…I have been at the Ohio specimen, visiting years ago with ODNR Division of Forestry’s Ann Bonner and Barb Fair (now on the faculty of North Carolina State University) and it is quite remarkable.

The Yale graduate Gifford Pinchot was the first head of the U.S. Forest Service, appointed by President Teddy Roosevelt. For wonderful stories of Roosevelt and Pinchot, check out “Wilderness Warrior” by historian Douglas Brinkley (and his FDR book “Rightful Heritage”). Pinchot was involved in some high-profile struggles.

One was with Richard Ballinger, Secretary of Interior in the Taft administration over adherence to Rooseveltian conservation philosophy. A second was with Yosemite’s John Muir over Muir’s concept of “preservation” of wilderness area untouched vs. Pinchot’s and TR’s concept of “conservation” and utilization of wilderness for the public good. He later became the Governor of Pennsylvania.   

Must check it out – when travel once again is doable. 

Our second story is of: the Buttonwood Agreement. I say “our” because if I do not tell at least some of this story, Joe Boggs has agreed to disinherit me (We have co-joined West Virginia Wills, and we are allowed to say so since we are both Almost Heaven natives). Not to mention the fact that he is 99% as smart as me; wait, what does that mean, does that extra 1% mean that he is smarter or less smart than me?). I prove my point. 

Buttonwood Agreement. From Wall Street JournalButtonwood Agreement picture. From Wall Street Journal.

May 17, 1792. Two dozen monied New Yorkers signed said Buttonwood Agreement, launching the first New York Stock Exchange. Under a buttonwood tree, the largest tree around,Platanus occidentalis.“Button” because the wood of sycamore makes nice buttons. That’s where the 1% comes into play.

Want to know even more about planetrees and the Buttonwood Agreement, with many wonderful pictures, including their sensational flowers? Check out bygl.osu.edu/node 939, Joe Bogg’s “Ode to the Buttonwood.”