To this day, its origins remain a mystery. But somehow, amid the chaotic meeting of the so-called New World and the Old, two plants from continents thousands of miles apart — an American sycamore and an Oriental plane – met and reproduced.

                                ~ Zaria Gorvett

One of the nice things about the old neighborhood where I live is the sidewalks and street trees. New subdivisions seem to disdain traditional sidewalks and tree lawns — that strip of grass between the sidewalk and the curb. In the older neighborhoods in Golden, the tree lawn is planted with … street trees. Green ash are prevalent, and many of the old silver maples are gone or decrepit, but the city and homeowners have been quick to replace them. The city even makes it their job to maintain the street trees, routinely.

Most people treasure their tree lawn trees, and much of the current wide variety in species is due to owner-replaced trees, even though the city will replace trees if needed. Lindens are popular, as are horse chestnut, bur oak, various maples, crabapple, fir and elm. Variety is important so as to avoid wholesale destructions like when chestnut blight decimating millions of trees simultaneously in the early 1900’s, and Dutch Elm disease destroyed trees in the 1960’s and ‘70’s.

But today’s street trees still face challenges. Zaria Gorvett reports, “In fact, there’s emerging evidence that urban trees share many of the burdens of other city residents — often living in cramped conditions, riddled with infectious diseases, and suffering from chronic stress. In this unnatural setting, they tend to live fast and die young — research has found that they have mortality rates nearly twice as high as those in rural areas, with fewer surviving trees every year … Without a radical rethink of the living conditions of this long-overlooked community, some experts are concerned that our cities could soon lose much of their greenery altogether.”

The city of London found a new species of tree that suited their street tree needs perfectly. Gorvett explains that, over time, “Explorers and merchants sent these tiny souvenirs back from wherever they travelled — so as the map expanded, so did the plants available in Britain … But somehow, amid the chaotic meeting of the so-called New World and the Old, two plants from continents thousands of miles apart — an American sycamore and an Oriental plane — met and reproduced … Within a century these noble plants, the London plane tree, could be found scattered across London.

“Even as the harsh living conditions of the Industrial Revolution began to take hold, London plane trees continued to cling on where others got sick. In addition to being unusually hardy, the hybrid giants had some quirky features that helped them adjust to city life, such as the ability to slough off the outer layers of their smog-coated trunks to reveal a fresh patchwork of green and white bark beneath.

“But life for this Londoner has not been easy. Hemmed in on one side by buildings and the other by a road, it inhabits one of the most polluted parts of the city. And like most urban trees, when it rains it’s either inundated with runoff or left thirsty. Its roots are squashed into heavily compacted, alkaline soil – with little space to stretch out their tendrils without bumping into concrete.”

Space, moisture, pollution, lack of soil nutrients, all can cause stress, creating opportunities for pathogens, pests, etc. to damage the trees. Urban trees also have another potential enemy: people. Whether it’s weed-whacking at the base of the tree cutting the tender bark, lovers carving their initials in the trunk, or kids breaking branches as they eagerly climb trees to explore the world, urban trees can take a beating, causing not only direct damage, but stress.

We take care of our houses — we paint and repair and renovate. We mow, water, feed and weed our lawns. We tend the flower and garden beds every year. But most of us tend to ignore our trees, which are probably the greatest home asset we have and the hardest to replace. After all, as the old adage goes, “The time to plant a tree was twenty years ago.”

And, of course, Joyce Kilmer wrote:

I think that I shall never see
A poem lovely as a tree.

A tree whose hungry mouth is prest
Against the sweet earth’s flowing breast;

A tree that looks at God all day,
And lifts her leafy arms to pray;

A tree that may in summer wear
A nest of robins in her hair;

Upon whose bosom snow has lain;
Who intimately lives with rain.

Poems are made by fools like me,
But only God can make a tree.

Additional information:

Zaria Gorvett, The Hybrid Tree That Conquered The World, 1st June 2022, BBC

Joyce Kilmer, Trees, 1913