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Cracking the Case: A Look Inside the Nuts of Trees

This time of year, the leaves are falling; the trails are littered with tree seeds; and squirrels, chipmunks and similar critters are darting around the forest looking for last-minute meals to stash away for winter. Seed shells and remnants of snacks are scattered along trails.


A fox squirrel sitting in the crook of a tree while eating a nut.
A fox squirrel with a nut. (Photo courtesy of Chad Morsch)

One of the most recognizable seeds falling are acorns. Squirrels love acorns. But do they eat them whole? Do forest animals feast on a variety of things? Let’s investigate some of things falling from trees this time of year.   


What’s inside an acorn?  


Just like the leaves of oak trees, the seeds, or acorns, have a similar shape but vary slightly from species to species. In general, all acorns have a “hat” and a shell. But those outside parts are not what gets nibbled on.


If you’re thinking that there’s something inside the acorn, you’re right! Plenty of animals, even humans, break open the shell to eat the nut meat inside. This “meat” is loaded with protein, carbohydrates and fat, making it a hearty meal in the wintertime. 


A diagram of the inside of an acorn. (Illustration via Creative Commons)

Look at the diagram of an acorn. Learn more about the various parts:


  • A. Cupule: The “hat” of the acorn. This connects the acorn to the tree and protects the seed.  

  • B. Pericarp: The shell that we see fall to the ground.  

  • C. Seed coat, or testa: Think of this as a candy wrapper protecting the sweet treat.   

  • D. Cotyledons, E. Pumule and F. Radicle: Collectively, these parts make up the embryo, or “meat” portion of the acorn. This is what those hungry squirrels are after! But if forgotten about in a squirrel’s cache of food, this is the part of the plant that eventually grows into a tree.  

  • G. Remains of style: A part used in the reproduction of the tree. 


Now that you’ve seen a diagram, can you find these specific parts on the real acorns pictured below? 


Two acorns, one whole and one cut down the middle, on a white table.
A whole bur oak acorn and another cut down the middle. (Photo by Jenna Krukowski)

 

What’s inside a Kentucky coffeetree pod? 


Is that an overripe banana hanging from that tree? Nope! It’s a seed pod from the Kentucky coffeetree. In the spring, these pods are a vivid green that blends in with the leaves. As the seasons wear on and the leaves fall, the pods also change color. As the seeds age, they become hard and turn dark brown.  


Seed pods from a Kentucky coffeetree cracked open on a wooden table.
Kentucky coffeetree seed pods. (Photo by Jenna Krukowski)

The seeds, pods and leaves contain a compound called cytisine, which is toxic to humans and wildlife. After some dangerous trial and error, humans have found a way around this. They roasted the beans just like coffee. Those who didn’t roast the beans long enough found out the hard way that ingesting cytisine can cause diarrhea, vomiting and, in extreme cases, death. While these pods are an interesting and natural part of the tree, they’re not on the hibernation menu for woodland mammals.   


What’s inside a walnut?


This time of year, you might see right green balls about the size of a golf ball lining pathways in the preserves. Although these are “fruits” of a tree, it’s not the sweet kind you’re thinking of. These green balls contain walnuts from black walnut trees.  


Whole and cracked open black walnuts on a burlap surface.
Black walnuts. (Photo via Shutterstock)

The green part you see is not the walnut itself, but the husk. These husks can be heavy and protect the shell of the walnut, which looks like a ball of tree bark. If you are strong enough to open one (They’re literally a tough nut to crack!), you will find some nut meat, or the part that’s meant to be eaten. 


Black walnuts are one of the most populous trees across this part of the country, so many humans and animals, like fox squirrels, birds and other rodents, munch on these walnuts.


 

Words to know

Cache: A collection of items stored in a hidden place.

Culinary: Related to cooking.

Immature: Not fully developed.

 

Keep an eye on the details — the walnuts you will see in the aisles of your local grocery store are not black walnuts. They’re most likely English walnuts, which have a less bitter taste. Yet that distinct, bitter taste of black walnuts has been welcomed in sweet and savory dishes by many people. 


In addition to culinary use, the walnuts have been used over time as a dye. The immature green husks will dye hands yellow, and darker husks will dye sidewalks, hands and anything else various shades of brown. Be careful if you decide to pick one up! 

 

How do the seeds of the black walnut compare to acorns? 

  

Bonus: What’s inside a milkweed pod? 


Milkweed is a plant, and its pods don’t fall off trees, but it is another interesting pod you will see in the preserves. Over the spring and summer, common milkweed produces beautiful pink flowers and is home to monarch caterpillars and butterflies. In the late summer and fall, these pods open to reveal tiny brown seeds attached to white fluff called floss.


Dried and split open milkweed seed pods with silky floss and seeds spilling out.
Milkweed seed pods. (Photo by Anthony Schaklk)

This incredibly light, soft floss flies in the wind, helping to spread the seeds. Sometimes, the floss gets stuck in the pod. This fluff is still useful. Birds and small critters will use it for their nests and homes.  

  

Next time you plan to visit the preserves, don’t forget to pack your curiosity and magnifying glass to investigate just what is inside. 

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