I first heard this statement many years ago. Occasionally, I still hear some version of this claim: Black walnut engages in warfare by releasing a chemical into the soil. This chemical kills or inhibits the growth of plants.
But is this entirely true? Does black walnut actually kill plants?
Some people say yes. Other people say no.
In a brand-new video, I share several key findings from scientific studies and personal observations that shed some light on this controversial topic.
I’m excited to announce that I’ll be leading a Summer Forest Ecology Outing in a few weeks, and I’d love for you to join me!
This outing offers a unique in-person opportunity to learn the fascinating ecology and geology of a remarkable area: McConnells Mill State Park in Pennsylvania.
Designated a National Natural Landmark for its outstanding features, McConnells Mill State Park is a treasure trove for learning. Central to the park’s landscape is the Slippery Rock Gorge — a deep ravine carved by powerful forces, exposing millions of years of ancient bedrock and currently supporting mature forest ecosystems.
During this outing, we will walk through deciduous and coniferous woodlands while discussing forest ecology. We’ll investigate big trees and big rocks. We’ll see historic landmarks, and we’ll discuss important geological influences that have drastically shaped the landscape.
In addition to learning key characteristics of mature forests, participants will learn tree identification techniques, mushroom ecology and identification, the influence of glacial activity on landscape development, ways to interpret forest history, and much more.
This outing is the perfect opportunity to learn, explore, and connect with nature in a truly spectacular setting.
Interested? Here are the details:
When: Saturday, July 12 or Sunday, July 13, 2025 (Choose one date; both programs will cover the same material.) Where: McConnells Mill State Park, Pennsylvania Time: 10:00 am — 4:00 pm
To maximize your learning experience, space is limited and registration with payment in advance is required to secure your spot.
Every now and then, I’ll come across a decent-sized American chestnut and wonder: “Just how big did these trees get?”
I’ve always read that American chestnut was a dominant tree throughout eastern North American forests. I’ve heard people describe American chestnut as a tree that towered above all others. I’ve even seen references to American chestnut as “the redwood of the east.”
But how much of this is true? Was American chestnut an exceptionally massive tree?
Unfortunately, it’s difficult for us to know for sure. A fungal disease known as chestnut blight killed nearly every large American chestnut throughout the first half of the 1900s. Today, American chestnut still exists on the landscape, but almost always as a smaller tree.
Ecologists in recent years have been wondering about the size of American chestnut in pre-blight forests. I’ve been wondering about it too, which is why I decided to film a video on the topic. It turns out that we may have some answers after all.
Has the size of American chestnut been exaggerated in recent decades? What do sources from the 1800s tell us?
I’m really excited to announce that I’ll be leading an Old-Growth Forest Ecology Outing in a few weeks, and I’d love for you to join me.
This outing offers a unique in-person opportunity to learn the rich ecology and distinctive features of older forests.
We’ll begin the day by walking through a mature upland hardwood forest and discussing forest ecology. In the afternoon, we will explore a magnificent old-growth conifer forest and discuss old-growth forest dynamics.
In addition to learning key characteristics of mature and old-growth forests, participants will learn tree identification techniques; mushroom ecology and identification; the influence of geology on forest development; ways to interpret forest history; the role of fire as an ecological agent; old-growth forest misconceptions; and much more.
This event will take place in Cook Forest State Park. Located in northwestern Pennsylvania, Cook Forest is home to one of the last remaining old-growth forests in the entire region, currently hosting 11 old-growth areas totaling over 2,300 acres. One of the areas within the park, the Forest Cathedral, contains arguably the finest concentration of old-growth trees in the northeastern United States. This remarkable area is home to dozens of old-growth eastern white pine and hemlock trees, many over 300 years old and towering above 140 feet in height.
This outing is the perfect opportunity to learn, explore, and connect with nature in a truly spectacular setting.
Interested? Here are the details:
When: Saturday May 31, 2025 or Sunday June 1, 2025 (Choose one date; both programs will cover the same material.) Where: Cook Forest State Park, Pennsylvania Time: 10:00 am — 4:00 pm
To maximize your learning experience, space is limited and registration with payment in advance is required to secure your spot.
To find good medicine, look in a forest. In a forest, you’ll encounter plants that have the ability to heal human ailments.
Many years ago, I learned about the medicinal properties of a particular woody plant. This woody plant, when applied to my face as an extract, improved my poor complexion.
Over the years, I’ve been able to maintain a decent complexion thanks to this plant (and thanks to significant lifestyle changes). While I no longer rely on this plant to heal my physical ailment, I do rely on it to address an existential problem.
Plaguing the human species, this problem can be solved if we know where to look.
I’d also like to mention that I’ll be part of the Wild Ones Western PA Chapter’s annual symposium on March 26, where I’ll be joining a panel discussion focused on strengthening communities and native habitats.
Humans try to avoid these four conditions. Old trees embrace them.
This is why I advocate taking long walks in the woods. In wooded ecosystems, we sometimes discover the ragged splendor of old trees.
On a recent walk in a hardwood forest, I rediscovered a tree I had first encountered many months ago. Rough, weathered, worn, and warped, it’s one of the most remarkable trees I have ever seen.
Want to improve your winter tree identification skills? Here’s a good tip: Look for marcescent leaves.
Marcescence describes leaves that have turned brown and are still attached to trees. These withered leaves often persist on the trees until spring.
As you might expect, marcescence isn’t a feature displayed by too many woody plants. When you see a marcescent tree or shrub, you can narrow down your ID choices to a relatively small number of species.
In the temperate woodlands of eastern North America, marcescence is often displayed by hornbeam (Carpinus), beech (Fagus), witch-hazel (Hamamelis), hophornbeam (Ostrya), and oak (Quercus).
No one is exactly sure why marcescence exists. Here are a few hypotheses:
It allows plants to photosynthesize longer into the autumn season.
It deters herbivores from browsing twigs and buds.
Marcescent trees provide shelter to animals that in turn provide nutrients to trees.
Marcescent leaves, when they finally fall off, provide pulses of nutrients to their host trees.
Marcescent leaves, when they finally fall off, smother new growth of competing woody plants in the spring.
All of these statements can be true to some degree, but it is uncertain whether any one of them is the true reason for marcescence.
Still, you and I can use marcescence to our advantage when attempting to identify woody plants. A good first step is to learn which woody plants are marcescent in our region. We can then seek out these plants, spend some time with them, and fall in love with the process.
To learn even more tips for identifying trees, consider enrolling in Trees In All Seasons. Today is the final day of the winter sale.
Also, if you’re interested in learning how to forage mushrooms this winter, consider enrolling in Foraging Wild Mushrooms. This 4-season online course is on sale until the end of today, December 23.
“The wonder is that we can see these trees and not wonder more.”
It’s no surprise that Ralph Waldo Emerson wrote these words. The famous American writer was intimately connected to trees: He planted trees, gathered their fruits, and taught his children the value of learning their names.
Emerson spoke the language of trees, yet was still humble enough to acknowledge that every encounter with trees presented a fresh opportunity to engage in wonder.
Who are you? How old are you? Why are you here? Can you say anything about the underlying rocks? What can you tell us about the broader ecosystem?
In the spirit of Ralph Waldo Emerson, you and I can ask these kinds of questions every time we encounter a tree. When we ask questions, we engage in wonder.
A basic step we can then take to answer those questions is first to learn the names of trees. Fortunately, there are many ways to learn. We can:
Study tree ID field guides
Learn how to use dichotomous keys
Learn all major physical features of trees (buds, bark, leaves, flowers, etc.)
Learn habitat characteristics of trees
Attend tree ID walks
Visit arboretums (where trees are often labeled)
Cultivate friendships with local tree enthusiasts
Teach others what we have learned
If you’re looking for a carefully curated opportunity to improve your tree identification skills, consider enrolling in Trees In All Seasons. This online course teaches you how to identify 100 trees in every season. It’s currently on sale through Monday, December 23.
Regardless of how you decide to learn, I strongly encourage you to hone your tree identification skills over time. With learning comes wonder, appreciation, love, and the unraveling of at least some of nature’s mysteries.
It isn’t an easy question to answer, but I try my best to explain what it is about trees that makes me feel good.
I love the food trees offer. I enjoy the medicine trees provide. I like the shade trees cast. And I admire their beauty.
But there’s something else about trees I really appreciate: their ability to tell stories.
As it turns out, trees tell remarkable stories of peace, tragedy, death, and — believe it or not — democracy.
One notable tale that trees tell quite well is the story of America’s birth as a nation. While many people associate this story with icons like the Liberty Bell and the Declaration of Independence, the founding of the United States is also strongly connected — both physically and symbolically — to one particular tree.
Tall, majestic, and extremely useful, this tree has been famously labeled “the tree that built America.”
Speaking of trees, I was recently interviewed on Harvesting Nature’s Wild Fish and Game Podcast. In the interview, we discussed how trees can help you become a better hunter and observer of wildlife.
This course is designed to improve your ecological knowledge by introducing you to fascinating ecosystems — including alvars, barrens, bogs, dunes, fens, glades, savannas, vernal pools, and others!
Learning to recognize ecosystems is an essential step toward understanding how nature works. When we pay attention to the bigger picture, we see beyond individual components. We see connections, we see relationships, and we see where humans fit into the story.
If you want to develop ecological literacy; if you want to be able to read landscapes more effectively; if you want to see how all the components within nature are connected, consider enrolling in Exploring Wild Ecosystems today.
Please note that Exploring Wild Ecosystems is open for one week only — from today until Monday, September 30. After that, registration will be closed. Upon registration, you can immediately access all course content and view the lessons at your own pace.
To learn more about the course, check out this video which gives you an overview of what you can expect.
Thanks for supporting nature education! I hope to see you in there!
Paths I Walk 
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