Plane trees

Handel's famous "Largo", best known as ecclesiastical music, began life as a love song --- to a plane tree. The title character of Handel's opera Xerxes makes a fool of himself in the opening act, pouring out his love to a plane tree in the aria "Ombra mai fu", (Never sweeter was the shade of any dear and lovable plant.) Not the first time or the last that the Persians would get bad press in the West or that someone would fall in love with a tree.(1)

Xerxes' beloved plane tree was an Oriental plane tree, one of the parents of the London plane tree that is common on the streets of Plainfield. The other parent is the American sycamore. The two parent species diverged at least 50 million years ago. They evolved separately thousands of miles apart, but were brought together in 17th Century European botanical gardens, where they produced hybrid offspring: the London plane tree.(2) Plane trees get special notice in botany textbooks under the heading, "What is a species?" As a rule, members of a species produce fertile offspring by breeding only with each other, not with members of other species. London plane is an exception to that rule. Like mules, London planes have parents of two different species. Unlike mules, London planes are fertile.

Why "London" plane? During the sooty days of the industrial revolution, the trees were planted in large numbers in London because of their great pollution tolerance. The trees' peeling bark helps them shed damaging pollutants.(3) Sixty percent of London's street trees are said to be London plane trees.(4)

City Councilman Rashid Burney drew my attention to the plane trees of Cedarbrook Avenue. I haven't heard him singing, but I have heard him wax quite lyrical on the subject. Cedarbrook Avenue's street trees are almost all mature plane trees. Their branches merge to form a cathedral-like vault of foliage for almost the entire length of the street. Even when the trees are leafless, they sustain visual interest with their multicolored, peeling bark and the regular rhythm of their placement as one progresses along the street.

The hybrid London plane tree is used in preference to the American sycamore for street tree planting because it is slightly smaller and more disease-resistant. Most of Plainfield's plane trees are London planes, not sycamores. It can be difficult to tell the two species apart.(5) I would identify the two young plane trees on Hillside Avenue between 1108 Hillside and Thornton Avenue as sycamores. Note 5 below provides criteria for speciation.

American sycamores become hollow after about 100 years of age.(6) In centuries past, their hollow trunks provided ready-made barrels; larger trees served as temporary housing.(6) The trees continue to grow for centuries after becoming hollow, producing the largest-diameter trunks of any American hardwood.(7) George Washington measured a sycamore in Ohio at about 13 feet in diameter.(8) The most dramatic account of the huge size of a sycamore was left by John James Audubon. I quote him at length, his words as lyrical as either Xerxes' or Burney's. He describes the early morning exit of a great flock of chimney swallows (chimney swifts) from the hollow trunk of a gigantic sycamore in which they had spent the night:

"Next morning I rose early enough to reach the place long before the least appearance of daylight, and placed my head against the tree. All was silent within. I remained in that posture probably twenty minutes, when suddenly I thought the great tree was giving way, and coming down upon me. Instinctively I sprung from it, but when I looked up to it again, what was my astonishment to see it standing as firm as ever. The Swallows were now pouring out in a black continued stream. I ran back to my post, and listened in amazement to the noise within, which I could compare to nothing else than the sound of a large wheel revolving under a powerful stream. It was yet dusky, so that I could hardly see the hour on my watch, but I estimated the time which they took in getting out at more than thirty minutes. After their departure, no noise was heard within, and they dispersed in every direction with the quickness of thought."(9)

(1) Herodotus' original telling has Xerxes adorning the tree with gold and setting a guardian over it in perpetuity.

(2) Peter H. Raven, Ray F. Evert, and Susan E. Eichhorn, Biology of Plants, W.H. Freeman and Company Worth Publishers, Sixth edition, 1999, p. 248. The "x" in the scientific name, Platanus x acerifolia, indicates a hybrid species. The oriental plane tree, Platanus orientalis, is native to southern Europe and Anatolia. The American sycamore, Platanus occidentalis, is native to eastern North America.

(3) Colin Tudge, The Tree: A Natural History of What Trees Are, How They Live, and Why They Matter, Crown Publishing, 2006, p. 157. Another feature that makes London plane suitable for street tree use is its ability to withstand extensive and even brutal pruning. Pollarding (maintaining the major limbs as short stubs by severe yearly pruning) is unusual in the U.S., but Europeans don't hesitate to pollard plane trees to restrain their size. Rows of pollarded plane trees are a very common sight in European cities.

(4) Arthur Plotnik, The Urban Tree Book, Three Rivers Press, 2000, p. 63.

(5) The most reliable criterion for speciation is the fruits, which occur singly on sycamores and in pairs on London planes. In addition, the leaves of sycamores are less deeply lobed, and their bark is said to be whiter. Although smaller than American sycamores, London planes are not small. The two tallest hardwood trees in Britain are London planes according to Thomas Parkenham (in Meetings with Remarkable Trees, Random House, 1997, p. 78).

(6) Donald Culross Peattie, A Natural History of North American Trees, Houghton Mifflin, 2007, p. 373.

(7) Peattie, cited above, p. 372.

(8) Peattie, cited above, p. 373. The same tree was also measured twenty years later by the great French botanist and explorer Andre Michaux. Peattie cites the largest sycamore on record as having been measured in 1802 at 47 feet in circumference, about 15 feet in diameter at breast height.

(9) John James Audubon, "The Chimney Swallow", excerpt from The Birds of America, quoted at greater length in Ohio-Birds: http://www.ohiobirds.org/news.php?News_ID=108

Copyright Gregory Palermo