Subscribe Today

Watoga Trail Report

The fruit of the black walnut tree. Photo courtesy of James DeMeres by Pixabay

The Dark Side of Black Walnut
La Femme Fatale

It is considered conventional wisdom by serious mushroom hunters that morels tend to pop up in greater than usual numbers following brush fires and forest fires.

I walked the railroad tracks on a lovely April day in 1961 with a favorite uncle who had been a railroad detective in his younger days. He was 61 at the time, and I know this because he was born in the year 1900, a date that makes it very easy to keep track of another’s age.

I was 12 years old at the time, and he and I were out for our annual mushroom walkabout.

Uncle Bud was a hilarious man, so much so that when he died in 1968, many of the bars in Lancaster, Ohio, closed for the afternoon of his funeral – bars where he had entertained patrons for decades with his ribald and witty humor.

They clearly loved him for his stories that came in two flavors only, funny or ironic, but always smart, no lowbrow stuff or bathroom humor.

We walked the tracks with the land on each side blackened by fire the previous November, most likely started by a spark ejected from a passing train during tinder-dry conditions.

Indeed, there were morels aplenty, and by the time we reached a trestle spanning Hunter’s Run a half-mile or so down the track, we had nearly filled up our bread bags with white morels, regionally called “white sponges.”

We paused about halfway across the bridge to gaze down into a deep pool situated under the cast-iron span. Uncle Bud shared memories with me about that swimming hole, dating back to when he was a teenager.

He talked about sneaking up on girls skinny-dipping in the pool and hiding their clothes.

As a budding young man I found this story of immense interest.

He mentioned a time in the 1920s when he witnessed a very prominent man in the area drive onto a bridge further downstream and dump something into the river, quickly driving away.

Years later he told this story in local bars, fostering much speculation about the item thrown into the drink. He was reluctant to notify authorities at the time because he was hiding moonshine for a customer pick up near the bridge; better to keep one’s mouth shut when both parties are up to no good.

He pointed out an elevated platform a few feet from the tracks that he explained was where the “third rail” ran to supply electricity to the inter-urban trains that ran between Columbus and Lancaster, Ohio.

Like black walnut, garlic mustard uses allelopathic compounds to control competitors. K. Springer photo

He said that he and his friends would rig up a wire tied to a rock which was then thrown into the deep water of the pool. The other end of the wire was affixed to a short section of tree limb and cast over the third rail, shocking the fish and bringing them to the surface. He spoke of taking home catfish and smallmouth bass that ended up in the frying pan.

Then, as if an afterthought, he said “We had another way to get fish out of this hole after the electric trains were abandoned in favor of the diesel freight trains.”

Uncle Bud explained that they would gather green walnuts in a burlap sack and smash the walnuts on the train track so that the hulls would release their dark liquid. They would then put a couple large rocks into the bag with the walnuts and throw it into the middle of the swimming hole.

He said that after a few minutes, fish of all types would rise to the surface of the pool, swimming on their sides as if stunned.

“You could just pick out the fish you wanted to eat and leave the suckers, carp and smaller fish to recover and swim away,” exclaimed Uncle Bud. He insisted that this was a fishing technique used by Indians.

I never had the opportunity to try this myself, but it was something I stored away in memory, in case I ever needed this curious bit of outdoor lore.

I was decades away from knowing about an organic compound called juglone, but I imagined that whatever was bringing the fish to the surface, must be something akin to curare.

Many movies in this time period portrayed explorers and missionaries who were paralyzed by curare tipped arrows shot from the bows and blowguns of indigenous South Americans.

It turns out that our black walnut tree, greatly admired for its beauty and fruit, also harbors a lethality for specific plants and an ability to harm some mammals and fish.

Once again, we have to turn to science for answers as to how and why a tree is equipped with such weapons.

And, that leads us to a term called “allelopathy,” broadly meaning, a biological phenomenon where an organism produces biochemicals that influence the germination, growth, survival and reproduction of other organisms, for good or harm.

This subject is quite complex so we won’t wade too far into the weeds today.

Garlic Mustard, notorious as an aggressively invasive plant, has been successful because of fast growth, numerous seeds and the release of allelopathic compounds that keep competitors at bay.

In the case of black walnut, the specific allelopathic compound is called juglone. The idea that one plant could chemically control other plants was originally controversial, but the work of science persevered and the active compound “juglone” was finally isolated in 1851.

Juglone was later accepted by mainstream science as an active herbicide and was eventually synthesized for medical uses and as dyes, particularly the dye for the reddish-brown color “henna,” as well as for herbicides and pesticides.

So, we have established in this discussion that the black walnut can cause harm to certain other plants, particularly eggplants, tomatoes, potatoes, peppers, some wildflowers and trees, as well as alfalfa and tobacco. And even some herbivore insects.

Juglone has been used for millennia to harvest fish, but can it really harm a mammal?

On a crisp fall morning in the early 1980s, Susie Hardesty went out to her barn to feed the Appaloosas she raised as show horses.  When she arrived at the stalls, one of her horses was shifting its weight from one hoof to the other. Fearing her horse was going lame, she called out her veterinarian for a look.

After arriving, the vet quickly diagnosed her horse as having laminitis, an inflammation of the laminae in the hoof. This condition is painful for the horse, and if left untreated, can cause deformation of the hoof and permanent lameness.

The horse was treated with medicine, and before departing the vet asked Susie if there was any black walnut in the horse’s bedding. She immediately called the sawmill where she had got a truck bed full of shavings the previous week.

Sure enough, Susie was told they had sawed a run of hardwoods during that time period, including black walnut.

To be fair to our beloved tree, the black walnut exercises an ability to help other trees and plants at the mycorrhizal level. This is where nutrients and minerals are obtained and shared by trees through a subterranean fungal network.

So although the black walnut will not allow the approach of many plants it deems poor company, it will send some of its own sugars to trees in need. But the gratitude for this act of altruism must be shared with the facilitator and courier, the mother of mushrooms, mycelium.

Ken Springer

more recommended stories