Thanksgiving Treets: Walnuts

By Dylan Stuntz, American Forests

Our final Thanksgiving Treet features the walnut!

The common walnut (Juglans regia), also called the Persian walnut or English walnut originated in Central Asia, with some legends positing that Alexander the Great exported walnuts to Greece, spreading the tree across the Mediterranean. The common walnut is the edible variety most often grown for commercial distribution.

The black walnut (Juglans nigra) and butternut walnut (Juglans cinerea) are other members of the walnut family native to North America. Both trees are native to the central and eastern U.S., but most commercial walnut production occurs along the Pacific coast, so neither tree is produced commercially on the same industrial level as the common walnut.

Walnuts will release into the soil a biochemical called hydrojuglone that, when exposed to soil or air, converts to the chemical juglone, which is toxic to many other species of plant. As a result, walnut trees will often be free-standing, with few other plants or trees found in a radius around them, thus eliminating potential competitors for resources. Black walnuts release a higher amount of juglone than butternut or common walnuts, making black walnuts difficult for commercial orchards to produce.

The walnut is not a true nut, rather instead it is instead the seed of a pseudodrupe, meaning that the “shell” of the walnut is actually a pit found inside the fruit of a walnut tree. There is some debate among the scientific community as the designation of walnuts as a pseudodrupe, with some researchers instead calling it a “drupaceous nut.” Regardless, after a walnut flower is pollinated it produces a dry green husk around a harder inner pit. The pit is considered to be the “shell” of the walnut, and the edible walnut is the seed of the tree found inside the pit.

Walnuts are deciduous trees growing between 60 to 80 feet tall. The walnut tree has leaves that are a brighter and yellowish shade of green compared to many other trees, alternating along the branch and forming later in the spring than many other trees that share similar habitats. The tree will flourish in light-intensive environments and is capable of pollination from heavy winds.

Almost half of the approximately 3 million annual tons of walnuts comes from China, with the U.S. and Iran coming in as the next-biggest producers, each producing 16 percent and 14 percent, respectively. While most commercial walnuts sell only the nutmeat, the shell can also be broken down for ink and oil. It’s thought that Leonardo Da Vinci may have experimented with walnut oil while writing some of his notebooks!

Sweet Potato Walnut Casserole


  • 3 lbs. sweet potatoes, peeled and cubed
  • 3 tbsp. canola oil
  • 2 tbsp. butter
  • ½ tsp. vanilla
  • ¼ cup packed brown sugar
  • ¼ cup maple syrup
  • 1¼ tsp. kosher salt, divided
  • 1 tsp. cinnamon
  • ½ cup orange juice
  • Cooking spray
  • 1 cup raw oats
  • 2/3 cup coarsely chopped walnuts, toasted
  • 1½ tbsp. all-purpose flour


  1. Preheat oven to 375 degrees F.
  2. Bake potatoes for 10-15 minutes, until soft (toothpick or fork should come out clean).
  3. Heat oil and butter in a medium skillet over medium heat until butter melts. Add vanilla to oil mixture; cook 30 seconds. Remove pan from heat; let stand 10 minutes.
  4. Add maple syrup, 1 teaspoon salt, cinnamon and orange juice to potatoes. Mix by hand with a masher. Spoon potato mixture into an 11 x 7-inch baking dish coated with cooking spray.
  5. Add oats, walnuts, flour, sugar, and remaining ¼ teaspoon salt to butter mixture; toss. Sprinkle over potato mixture. Bake at 375° for 35 minutes or until bubbly around the edges.

American Forests wishes you and yours a very happy Thanksgiving!