How to Identify a Black Walnut Tree

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Black walnut trees are some of the most widely-grown trees in North America. Just like the name implies, they produce walnuts, making them very valuable plants. You can usually find them in forests stretching from the east coast of the United States to the Midwest. If you’d like to do some tree-spotting, the black walnut is easy to identify from spring to autumn because of its distinctive leaves. It’s more difficult in the winter, but there are still physical signs you can use to spot the trees. When you know what to look for, you can find black walnut trees any time during the year.

Method 1
Method 1 of 2:

Recognizing Leaves, Buds, and Branches

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  1. The walnut tree’s leaves are its most distinctive feature during the growing season. They grow in a green twig that’s about 1–2 ft (0.30–0.61 m) long and sprouts from the branches. [1] Each one of these twigs can have 15-24 leaves sprouting along each side. [2] The twigs are concentrated at the end of the branches, so you’ll see pinnately compound green leaves around there. [3]
    • The leaves have an irregular oval crown (meaning they're oval-shaped with a thin tip at the end). They're usually light green in the spring and summer, and turn bright yellow in the fall. [4]
    • The walnut tree should have leaves from April until about November, depending on the temperature. You can spot the trees more easily during these months. [5]
  2. Between April and June, walnut trees produce flowers that grow along the branches and behind the leaf buds. They usually grow upwards, but they’re soft, so they droop over the branch and point down when they’re long enough. Look for these flowers during the spring months to identify walnut trees. [6]
    • When the flowers are still growing, they look like tiny cactuses coming out of the branch.
    • These flowers don’t produce a bud like the flowers you might be thinking of. If you don’t know what they are, you might think they were a different type of leaf.
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  3. These green globose fruits contain the walnuts, but they don’t look like any walnuts you’ve seen before. The husk around the nut is green at first, then gradually turns brown as it ripens in the late summer. When the fruit is full-sized, it resembles a lime. They grow in bunches of 3 or 4 at the end of each branch near the leaves. [7]
    • Mature trees start growing fruit as soon as spring starts, so you should be able to spot fruits from the spring to autumn. In the spring, the fruit will only be small green buds at the end of the branches, so it might be tougher to spot.
    • Trees usually don’t start producing fruit until they’re 10 years old. Learn to rely on other identification methods like the leaves and flowers to find immature trees.
  4. In the winter, you can't rely on leaves and fruits to identify the tree. However, there are some smaller growths that you can use to spot the tree. The terminal bud is where the fruits grow from. This is a rounded tip on the end of each branch. It’s usually gray in color and slightly fuzzy. [8]
    • The buds may be tough to see if the tree is very tall. A pair of binoculars will make this easier.
  5. Look alongside the twigs for small, rounded protrusions. These are the bud that the leaves sprout from. They’re also gray in color, in contrast to the brown or green twig. This is another helpful identification tip in the winter. [9]
    • The twigs may have slight notches where the buds sit. These are scars from the previous year’s leaves.
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Method 2
Method 2 of 2:

Checking the Tree's Physical Characteristics

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  1. Walnut trees are tall and are often some of the tallest trees in the area. Their average height is 70–80 ft (21–24 m), but they can even reach up to 150 ft (46 m) on rarer occasions. If you don’t know where to start, look for the tallest trees in the area. [10]
    • On average, grown walnut trees are 2–4 ft (0.61–1.22 m) in diameter.
    • This isn’t the most reliable method since trees could still be growing, but the height is probably the first thing you’ll notice. Full-grown walnut trees are usually the tallest in the area, so looking for a tall tree can give you a good starting point.
  2. If it’s wintertime and you can’t use leaves or fruit to identify a walnut tree, the tree's bark is a distinguishing characteristic. The bark has deep ridges that, from a distance, resemble a diamond pattern. This is a good early sign that you’re looking at a walnut tree. [11]
  3. Walnut tree twigs aren’t solid all the way through. They have a spongy interior that looks slightly like honeycomb sections. Try picking a twig off and cutting it longways. If you see horizontal ovals along the length of the interior, this is a telltale walnut tree sign. [13]
    • Be careful when using a knife. Wear gloves to avoid cutting yourself, and don’t hold the twig while you’re cutting it.
    • Try to pick up a twig that fell off instead of cutting one off the tree. This could damage it.
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  • Question
    How do you tell if a tree is a black walnut?
    Michael Simpson, PhD
    Registered Professional Biologist
    Dr. Michael Simpson (Mike) is a Registered Professional Biologist in British Columbia, Canada. He has over 20 years of experience in ecology research and professional practice in Britain and North America, with an emphasis on plants and biological diversity. Mike also specializes in science communication and providing education and technical support for ecology projects. Mike received a BSc with honors in Ecology and an MA in Society, Science, and Nature from The University of Lancaster in England as well as a Ph.D. from the University of Alberta. He has worked in British, North American, and South American ecosystems, and with First Nations communities, non-profits, government, academia, and industry.
    Michael Simpson, PhD
    Registered Professional Biologist
    Expert Answer
    If you believe you found a black walnut tree, take a look at the ground under it. These trees produce a chemical from their roots called juglone that prevents some other plant species from growing around them and competing for resources.
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  • Question
    What type of leaves do black walnuts have?
    Michael Simpson, PhD
    Registered Professional Biologist
    Dr. Michael Simpson (Mike) is a Registered Professional Biologist in British Columbia, Canada. He has over 20 years of experience in ecology research and professional practice in Britain and North America, with an emphasis on plants and biological diversity. Mike also specializes in science communication and providing education and technical support for ecology projects. Mike received a BSc with honors in Ecology and an MA in Society, Science, and Nature from The University of Lancaster in England as well as a Ph.D. from the University of Alberta. He has worked in British, North American, and South American ecosystems, and with First Nations communities, non-profits, government, academia, and industry.
    Michael Simpson, PhD
    Registered Professional Biologist
    Expert Answer
    As you get closer to the tree, look for compound leaves that occur alternately along the stems that are over a foot long, and have around 23 leaflets.
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  • Question
    Do black walnut trees have a smell?
    Michael Simpson, PhD
    Registered Professional Biologist
    Dr. Michael Simpson (Mike) is a Registered Professional Biologist in British Columbia, Canada. He has over 20 years of experience in ecology research and professional practice in Britain and North America, with an emphasis on plants and biological diversity. Mike also specializes in science communication and providing education and technical support for ecology projects. Mike received a BSc with honors in Ecology and an MA in Society, Science, and Nature from The University of Lancaster in England as well as a Ph.D. from the University of Alberta. He has worked in British, North American, and South American ecosystems, and with First Nations communities, non-profits, government, academia, and industry.
    Michael Simpson, PhD
    Registered Professional Biologist
    Expert Answer
    Yes, the leaves of black walnuts have a very distinct smell! Crush one of the leaflets and see if your nose picks up a pungent odor, as that's a good sign that you found a black walnut tree.
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      Tips

      • Black walnut trees grow throughout the east coast of the United States from northern Florida to Vermont. They also extend westward and stretch from northern Texas to southern Minnesota. If you’re in a wooded area in these states, you have a good chance of spotting one. [14]
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      • The trees could grow out of their natural geographic area, but they’re probably on private property or in nurseries.
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      Warnings

      • Roots from the black walnut tree are toxic to some animals, especially horses. If you have a walnut tree on your property, keep your pets or livestock away from it.
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      References

      1. ↑ https://plants.usda.gov/factsheet/pdf/fs_juni.pdf
      2. ↑ Michael Simpson, PhD. Registered Professional Biologist. Expert Interview. 8 September 2021.
      3. ↑ https://www.theparklands.org/Blog/151/Can-You-Spot-a-Black-Walnut
      4. ↑ https://www.ag.ndsu.edu/trees/handbook/th-3-137.pdf
      5. ↑ https://naturalresources.extension.iastate.edu/forestry/iowa_trees/trees/black_walnut.html
      6. ↑ https://www.theparklands.org/Blog/151/Can-You-Spot-a-Black-Walnut
      7. ↑ https://naturalresources.extension.iastate.edu/forestry/iowa_trees/trees/black_walnut.html
      8. ↑ https://www.canr.msu.edu/news/wintertime_identification_of_black_walnut
      9. ↑ https://www.canr.msu.edu/news/wintertime_identification_of_black_walnut
      1. ↑ https://plants.usda.gov/factsheet/pdf/fs_juni.pdf
      2. ↑ https://www.theparklands.org/Blog/151/Can-You-Spot-a-Black-Walnut
      3. ↑ Michael Simpson, PhD. Registered Professional Biologist. Expert Interview. 8 September 2021.
      4. ↑ https://www.canr.msu.edu/news/wintertime_identification_of_black_walnut
      5. ↑ https://plants.usda.gov/factsheet/pdf/fs_juni.pdf

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