The Botany of the Black Walnut Tree

The Black Walnut tree can be very annoying with the nuts it drops, and the juglone it emits. But, learning how to use this very beneficial tree will give you a whole new perspective on those large annoying nuts, and how it can become a treasure for the brain and taste buds. For now, let us focus on properly identifying the black walnut tree.


Walnuts are found all over the world. There are 60 some species in the Juglandaceae (Walnut) family. The Black Walnut, Juglans Nigra, is native to the Eastern part of North America and can live up to 175 years. Butternut is another member of this family.


The black walnut is a large tree with an open round crown. It stands tall and proud with the most distinct and amazing odor that separates it from the other such trees in its family. I have a wonderful variety of trees in my yard and the black walnut is one of the tallest standing up to 75 feet tall. The deciduous tree is the first to lose its yellowish leaves come early Fall, and the last to grow its leaves come Spring.


Although the black walnut is native to the Eastern part of North America it can be found Westward. Actually, the biggest producers of black walnuts come from Missouri. Black Walnut trees can be found in areas where they receive lots of sun light and where the soil drains well.

I have three huge trees along the edge of my yard where it meets the river and a smaller one in the front yard. In the Spring, the river rises, and the flood waters come all the way up to the black walnut trees that border the yard. They don’t seem to mind all the water.


The trunk is straight, tall, and relatively skinny. The wood is prized for its strength and durability making it a very expensive wood. The bark is deeply grooved with a diamond like pattern and spewing different shades of gray. I have read that the older the tree the darker the gray but, I haven’t found this to be true, unless you are talking about the difference between a brand new sprouting tree verse a 50 year old tree.


A leaf of the black walnut is pretty-large growing from 12-24 inches in length. The leaves are pinnately divided containing about 15-23 leaflets, with each leaflet growing 3-4 inches. The tips of the leaflets are pointed, and the edges are very finely toothed. The top of the leaves are a yellowish green with a smooth surface, while the underside is a lighter shade, and can be a bit soft.  Most leaves have the larger leaflets at the middle section.

The leaves turn yellow in fall and begin to drop come end of September and through October. Come Spring, the Black Walnut is one of the last trees to grow in its leaves.  


Both male and female flowers are found on the same tree. Before we talk about the male and female parts, let’s talk a bit about the pollination process. Although both male and female parts are found on the same tree other black walnut trees are need for cross-pollination which is carried out by the wind. That is because on the one tree, the female part often matures before the male part does, thereby making pollination impossible. However, in cases where self-pollination has occurred the fruit, or nut, is not as large or good as that from a cross pollinated tree.

The male flower grows as a catkin with 3-6 sepals, 0 petals, 3-40 stamen. These catkins can be anywhere from 2-4 inches in length.

The female flowers have 4 sepals, 0 petals, and the pistil has 2-3 fused sepals where the pear-shaped ovary can be found and later develop into the black walnut.  Often, I see the black walnut fruit hanging on the tree in pairs.

Unfortunately I do not have any photos of the flowers. Hopefully I can get a few next season. Until then, Check out Seeing Trees, by Nancy Ross Hugo, for some amazing photos of Black Walnut trees. There is a black walnut segment where she shares some great information. But the images are the most fascinating. The book has great up-close pictures of both male and female flowers at different stages, and a really cool photo of the nuts cracked open. The photos were taken by Robert Llewellyn.

Here are some cool books on black walnuts. As an Amazon associate I earn from qualifying purchases.


Now we come to the nuts. Most people get to this point and are done. Ugh. Those tennis ball looking things. But really, they are pretty amazing once you learn how to remove the husk and crack into these tasty and nutritious nuts.

So, the exterior of the black walnut is a green shade much like that of a tennis ball, a yellowish green. It is a thick layer, about 1/4 inch, that emits a yellow juice that turns black once exposed to air.

Once you remove the husk, you get the shell which is light orange. Very quickly it turns to black because of the oxidation process. The shell resembles the tree bark in that it is grooved the same way. Compared to other nuts, the black walnut is difficult to crack into. It requires a bit more pressure which can be achieved by using a tool such as a hammer. If you can do it without the tool, sweet! Show me how. Check out How to Harvest and Crack Black Walnuts and I’ll show you how to get into these bad boys using a hammer.

Once inside a tan colored nut meat is snuggled tightly in its shell. It is aromatic and the meat is rich with flavor.


I pulled this baby black walnut tree, pictured below, from my medicine wheel garden. It shows the long-tapered root. As you pull on the truck, leaves, root, or fruit you get that wonderful aromatic quality of the tree.


The husks, leaves, and roots contain a chemical called juglone. Juglone doesn’t play nice with other plant so other plants won’t grow there. Unless its raspberries, then they will play nice. I know, I have both growing next to each other.

Another thing to know about black walnut trees…where there are black walnut trees you can be sure that babies are popping up like weeds in other parts nearby. Whether they were planted by squirrels, smashed into the ground from the kids stomping on them, or just naturally settled, they are around. Two of the larger trees are not far from my vegetable garden and every year I pull out walnut trees that are 3-4 feet tall. Man does it seem like they grow fast. I’ll swear that I’ve pulled them all out and the next week I find another.

There you have it… the botany of black walnuts. Once you get to know this tree it’s pretty awesome to have around. Stay connect to Wild Alex Herbs to get updates on recipes using black walnuts, and for journal entries that share the medicinal and edible benefits this delightful tree has to offer.

Learn how to harvest black walnuts and respectful wildcrafting techniques.

Written: November 19, 2019, by: Alexandra Stefanovic-Mundt, Founder of Wild Alex Herbs, Herbalist & Wildcrafter


  1. De la Foret Rosalee “Learning Your Plants, Walnut & Elm” Learning Herbs, Herb Mentor. Video Course: Learning Your Plants. Module 2; Lesson 23. March 21, 2012
  2. Elpel, Thomas J., “Botany in a Day, The Patterns Methods of Plant Identification, An Herbal Field Guide to Plant Families of North America”, 6th Edition. Hopps Press, LLc., Pony, Montana. January 2018. Page 90.
  3. Hugo, Nancy Ross. “Seeing Trees: Discover the Extraordinary Secrets of Everyday Trees”. Timber Press. Portland, London. 2011. Pages130-139.
  4. Tekiela, Stan. “Trees of Wisconsin: Field Guide”. Adventures Publications, Inc. Cambridge, Minnesota. 2002. Page193.

4 responses to “The Botany of the Black Walnut Tree”

  1. […] follow my Facebook page, or click on the follow blog button(s) to get journal entries including The Botany of Black Walnuts, The Benefits of Black Walnuts, and enjoy the recipe Balkan Pita with Black Walnuts & […]


  2. […] the black walnut. Consult a few different sources. Check out the entry by Wild Alex Herbs on the Botany of Black Walnuts. Once you’ve identified the black walnuts correctly, you may begin your […]


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