An online resource based on the award-winning nature guide

Mystery Photo: Young Eastern Black Walnuts

7-6-18 black walnuts IMG_8342Congratulations to “Deb” – the first person to correctly identify the subject of the most recent Mystery Photo as young Eastern Black Walnuts!

Eastern Black Walnuts (Juglans nigra) produce abundant tiny male flowers on long, dangling, finger-like catkins. Female flowers, located on the same tree as male flowers, are fewer in number and are slightly larger. Being wind-pollinated, Black Walnut produces female flowers with stigmas (the top-most, pollen-receiving structures) which have a large surface area designed to catch pollen drifting in the wind. (These are the “rabbit ears.”) The stigmas often persist while the fruit matures  — they are barely visible on the left walnut in photo.

By September, the walnuts will have matured. They then fall to the ground where their outer husk slowly decays. The fruits are well-known for leaching chemicals into the soil that inhibit the growth of other plants, an interaction known as “allelopathy” (literally meaning “making your neighbor sick”).

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7 responses

  1. Alice Pratt

    More learned…thank you! There must not be very many trees…..I’m sure I saw one on the Vineyard, many years ago.

    July 6, 2018 at 8:59 am

  2. Ben Falk

    Thanks! Don’t the roots also release juglone?

    July 6, 2018 at 11:17 am

    • Absolutely, sorry for not mentioning that they do!

      July 6, 2018 at 11:27 am

  3. I wonder if a stand of black walnut could stop the march of Japanese knotweed?

    July 6, 2018 at 4:40 pm

    • Wouldn’t that be great. I don’t know the answer to that, but I bet it might!

      July 6, 2018 at 4:43 pm

  4. Bill on the hill

    Hi Mary… This particular ” Mystery Photo ” was one of your better ones. Both my guesses missed the mark completely, however, I love the challenges of attempting to figure them out as I typically have a less than 10% success rate!
    The Japanese knotweed dilema is all over the northeast now, incl. my property.
    According to my forester, you can’t dig it up or burn it out to get rid of it. A chemical agent of some sort is what kills it and is the reason thus far why I am still putting up with this invasive species…

    July 7, 2018 at 7:57 am

  5. I’ve been seeing beavers eating Japanese knotweed, evidentally part of their summer fare. This is on the north side of Union St., Windsor, on the Mill Brook. This family of beavers is not enough to stop its march along the streambank though, which is why I was wondering about black walnut’s toxin.

    July 7, 2018 at 8:20 am

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