Category Archives: Education


In an earlier post, about American beech, I included a shocking confession: I tend not to get all hot and bothered when I see that someone has carved letters or an image into the bark of a tree. I know it’s wrong to injure a tree willy-nilly, but I can’t help myself. It’s the romantic in me, and maybe also the professor of literature and history.

Carvings on a beech tree in New York’s Central Park — is that an image of a tree carved on this tree?

It goes back quite a ways, this practice of carving upon trees.

Continue reading Arborglyphs

The Poetry of Trees

In my backyard stands an American beech (Fagus grandifolia), 20 years old.

American beech (photo from November 2018)

I know it’s two decades old because it was a gift to my wife from her sister on her 40th birthday in 1991. It’s meant to remind her of the copper beach (Fagus sylvatica f. purpurea) that grew in front of their childhood home near Philadelphia.

On any given day, American beech is my favorite tree. Why? Well, obviously, it’s that smooth, gray bark that draws the eye in a forest of furrowed, ridged, warty, and scaly trees.

Beech tree (center) in Springvale Park
Continue reading The Poetry of Trees

Also This

The other day I wrote about bark inclusion.

The UK arborist I mentioned there, Dr. Duncan Slater, has done extensive field work to document the conditions under which bark inclusion appears common.

It shouldn’t be a surprise.

If we start from the premise that, in the same way that our physical strength is developed by the strain we put upon our muscles, tree “strength” is developed in part by the strain that gravity and wind put upon wood, it makes total sense that anything preventing a tree from experiencing that strain can be detrimental to it.

And often it happens that a tree will be naturally deprived of that necessary stress or strain.

Credit: Duncan Slater

Slater calls these “natural braces.” For example, a branch from one of two equal-sized trunks of the same tree — these are called “co-dominant stems” or “double leaders” — may fuse with the second trunk. Obviously, the two parts of the tree are more nearly frozen in place. What Slater has discovered is that under such conditions, the junction between the two trunks is more likely to be weak due to bark inclusion.

So if that’s true, it’s obviously very important to eliminate a natural brace when a tree is young, but if a tree with a natural brace is older, cutting out a natural brace may be a recipe for disaster, i.e., a tree service may be increasing the chance of the tree splitting and falling on someone.

And look what I found recently in this Freedom Park oak with co-dominant stems:

Bark Inclusion

If you happen to be a tree, one of the bigger challenges you have is this: I need energy to grow and reproduce! So I’m gonna reach for sunlight, water, and nutrients. But how far and fast can I reach before something like this happens?

The photograph above shows an American elm (Ulmus americana ‘Princeton’) planted years ago by Tree Watch and Trees Atlanta in Freedom Park.

American elm is really great at reaching. It can grow fast. When it’s at home — ‘home’ being rich, alluvial soil in a forested floodplain along a river or stream — a tall American elm will have channeled so much of its energy into growing upward, in order to reach that lovely sunlight at the top of the forest, that it may have no branches at all until the 50- or 60-foot mark.

Photo credit: Christian O. Marks

Of course, an American elm growing in an open, grassy section of Freedom Park has no difficulty at all accessing sunlight. It’s like a kid left alone in a candy shop. (Think of that poor elm tree in Freedom Park as a kid with a terrible tummy ache.)

Continue reading Bark Inclusion

❤️ Weed Trees ❤️

Here’s a dictionary definition of a weed: “a wild plant growing where it is not wanted and in competition with cultivated plants.”

That definition leaves out a lot, doesn’t it? You hear the word “weed,” and somewhere in your mind you’re probably thinking “annoying” and “unsightly.”

People talk about “weed trees,” too. They spring up on their own, often in places where other trees may struggle to thrive or even survive. They’re exceedingly common. They may have characteristics that don’t fit the classic image of a tree, e.g., they may be bushy, misshapen, etc. And they’re scrappy: they can out-compete trees that we think of as conventionally beautiful, stately, grand, majestic, noble — all that good stuff.

Boxelder (Acer negundo) comes to mind. It’s a species of maple native to North America. Check out this guy. Talk about scrappy:

Photo credit: Arieh Tal

Here’s its compound leaf with leaflets (7 here but can be as few as 3), to help you identify the tree :

Photo credit: Glen Mittelhauser

Weed tree? Yet entomologist Doug Tallamy says 285 species of Lepidoptera (moths and butterflies) rely upon boxelder to survive their caterpillar stage.

So many bugs! Here’s the secret: boxelder is terrible at doing what many other trees do incredibly well, which is to seal off decay. Which means that boxelder rots. And what loves rotting wood? Bugs!

And birds love bugs, of course. So boxelder indirectly feeds lotsa birds, too.

Can you build a beautiful, long-lasting dining room table out of boxelder wood? Nope. But can you sustain an ecosystem encompassing hundreds or perhaps even thousands of different insect and animal species with boxelder trees? ? Yep.

From Ecology of Center City, Philadelphia by Kenneth D. Frank.

Yes, those are boxelder seedlings, bringing a stone staircase to life. Not bad for a weed.

Memorial Day 2021

In Marietta National Cemetery there lie not quite 19,000 graves of men and women who served their country. One of them is my uncle Robert Northington Hardeman III, known to his family and friends as Bobby.

He died, still a teenager, during the Battle of Saipan (June 15-July 9, 1944) in the Pacific.

Marietta National Cemetery, like many cemeteries, is a tranquil site, where many of the graves are shaded by mature trees.

Those trees are chestnut oak (Quercus montana), which is in the white oak grouping of oak trees.

The leaves of the chestnut oak have many shallow lobes, not unlike the leaf of a chestnut tree.

By the way, you do know how many wonderful trees you can find at Oakland Cemetery, don’t you? About 1,600, in fact. It’s a marvel. I highly recommend a walk there, sometime soon.


It’s that time of the year.

Chinese chestnut (Castanea mollissima)
Spiky flowers of the Chinese chestnut tree, called catkins.

A large Chinese chestnut tree (Castanea mollissima) is in bloom near my house, and it’s once again filling the air with an . . . ammonia smell which is seriously unpleasant.

The culprits are nitrogen-containing volatile organic compounds (VOCs) which include (for you chemists out there) 1-pyrroline, 1-piperideine, 2-pyrrolidone, and phenethylamine.

Chemical structure of 1-pyrroline

What’s the deal? Presumably the tree evolved this smell to attract pollinators. A recent scientific study of Castanea mollissima in China identified the chestnut’s pollinators as flies.

Those researchers suggest that we should add Chinese chestnut to the list of plants that rely upon sapromyophily for a reproduction strategy.

That is, this tree emits a smell that deceives carrion flies into believing that they’re visiting rotting flesh.


Naturally, I cannot help but imagine what it must have been like to be out in the forest when the mighty American chestnut (Castanea dentata), erstwhile queen of the mountainous forests in the eastern U.S., was in bloom.

And, hey, I’d happily cope with a couple of weeks of that yucky odor to have those trees back, safe and sound from the chestnut blight.


The next time you’re in the Poplar Circle area of Freedom Park, pause to admire this beauty.

Katsura (Cercidiphyllum japonicum)

Katsuratree comes to us from Asia — Japan and China to be precise — and we have this gentlemen to thank:

Thomas Hogg, Jr. (1819-1892)

Beginning in 1862, Thomas Hogg, Jr. was stationed at a new U.S. consulate at Kanagawa, south of Tokyo. The man knew plants. His father, an emigrant from Scotland to New York City, had operated a nursery on the site of today’s Madison Square Park (Broadway and 23rd) in Manhattan. Thomas’s brother James took over the business after their father died.

Immediately upon arriving in Japan, Thomas Hogg started sending home seeds of plants entirely new to North America. In the 1870s, he made a second trip to Japan and continued his collecting.

Everything from our wonderful Japanese maples to our evil, evil kudzu vines can be traced back to the industrious Mr. Hogg.

Inman Park is simply full of Hogg’s legacy, good and bad: fragrant snowbell, Japanese snowbell, Kousa dogwood, varieties of camellia, ‘Limelight’ hydrangea, oriental bittersweet, Japanese knotweed, and more.

He was justly proud of having introduced the katsura to these shores. Its botanical name is Cercidiphyllum japonicum (because its heart-shaped leaf is similar in shape to our redbuds, the genus of which is Cercis).

Katsura leaves (note the reddish color of new leaves)

In its natural habitat, katsura can grow quite large and live a long time. A man named Charles Sprague Sargent, who was the first director of Harvard’s Arnold Arboretum, had a photo taken of this tree on his trip to Japan in 1892. See how older katsuras tend to develop multiple trunks:

In fact, there’s a katsura on the grounds of the Arnold Arboretum with just such multiple trunks. This tree was grown from seed collected by another 19th-century botanist, a man named William S. Clark, during his 1876 expedition to Japan:

Arnold Arboretum katsura

There’s lots to love about katsura. Check out this fall foliage:

Katsura in autumn

Also in fall, the leaves emit a smell similar to caramel or cotton-candy, though not everyone can smell it. It’s generated by a chemical compound called maltol, which is also emitted by such items as bread, warmed butter, chicory, and cocoa.

Tale of An Oak Tree

When Jeanne and I moved into our Waverly Way home, back in the year 2000, there stood a huge water oak (Quercus nigra) between our house and our neighbor to the east.

Several years later, that oak died, and so our neighbor had to take it down. But it left some acorns behind!

In 2010, you can just see a sapling poking its head out of the bushes, in front of the flowering dogwood:

The next year, it’s making a bit of progress, though it’s hard to pick it out among all the other volunteers.

By 2014, with its root system just the way it wants it, the oak has leapt up.

Here is the tree now, on May 22, 2021. Roughly a decade of growth. It’s more than 60 feet tall. Look to the left. That’s a white oak (Quercus alba) that I myself planted probably five years before that water oak even thought about germinating.

Sixty feet tall in 10-12 years!

Sign the Inman Park Leaf Blower Petition

Gas-Powered Leaf Blowers in Inman Park

Residents of Inman Park in Atlanta, Georgia, should voluntarily restrict their use of gas-powered leaf blowers (GLB) to the following times and days: 10:00 a.m. to 4:00 p.m. from Monday to Friday, noon to 4:00 p.m. on Saturday, and not at all on Sunday.

Noise from GLBs is a source of unhappiness and inconvenience for many Inman Park residents. More than that, GLB noise can damage human health as well. The CDC, the EPA, and OSHA all identify leaf blowers as a source of harmful noise. Among the people most at risk are those who work from home, people who work night shifts, children, the retired, the elderly, the sick, and of course the landscape crew itself.

It's not just humans. A scientific study in 2018 found that the noise we humans generate affects wildlife, too. It alters stress hormones in birds, for example. One consequence is that chicks nearer to noise tend to be smaller, with poorer feather development.

Other negative effects of GLBs are well documented, especially with regard to air pollution. You could drive your car, with its efficient pollution-control technology, all the way to California, and you still wouldn't come close to producing the same amount of certain pollutants as GLBs create in the course of an ordinary day of leaf-blowing in Inman Park.

Alternatives to GLBs exist. A battery-powered blower is one example. More and more yard maintenance companies are going all-electric, including in Atlanta. Moreover, hundreds of cities and towns have already adopted restrictions on the use of GLBs.

By signing this petition, you are pledging to limit your GLB use (if any) to the specified days and hours, and you are encouraging others to abide by these modest, voluntary restrictions as well.

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