Can you post a leaf of the plant on which you found it? And was this found in the wild or was the plant placed in a garden?

I don't have the leaves. I could go back and get them though.

It's grown in a garden on the far-west end of the campus of The Ohio State University. Someone told me that Asian immigrants, maybe Vietnamese, rent plots of land over there and grow these. (I didn't know this when I took them).

It helps to provide those details so that people can be thinking about whether this is a native or an introduced plant.

It looks like an immature Butternut to me. Juglans cinerea. It would be from a tree with long, compound leaves, closely related to Black Walnut.

WW

Here is a link that might be useful: Butternut, Juglans cinerea

OK, today, in my neighbor's backyard, I found a ton of fruits that closely resemble the ones pictured above. I'm going to post several pictures below, of both the fruit and the tree. Do you think these are immature black walnuts?

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Definitely juglans.

The oxalis around the trunk near the bottom tells me that not much else would survive there, so perhaps juglone is at work....

Ignoring the first two photographs, do you have any idea what kind of juglans tree this is? I went to Wikipedia and around 30 different species are listed.

I ask you to ignore the first two photographs as those "immature walnuts" come from different species of tree. I'll try to get some leaf samples later this week.

In Ohio the only Juglans you'll find outside a botanic garden are Juglans nigra, Black Walnut, and Juglans cinerea, Butternut.

The first two pictures do look like Black walnuts. If you haven't got fruit it's hard to tell the difference between them; the best way is too look for the fuzzy 'mustache' at the top of the leaf scar on the Butternut. There's a picture on the link. (There's a picture of the 'mustache-less" bud on the Black Walnut page, only it's mis-labeled 'flower'.)

WW

The trees pictured look like the black walnut trees in my yard. About those fruits/nuts (hm. sounds like trail mix), do they have any fragrance when you scratch the surface? -perL

Yes, they smell like limes. That's why I called them a lime-like fruit.

As for the suggestion to look at the leaf scar, I don't see what you're talking about. I noticed that the leaf sample from the Butternut didn't have a leaf at the top of the stem, whereas the one for the Black Walnut does.

Any further clarification you could provide on this point would be much appreciated.

Here is a picture of a leaf scar.

This link has good definitions for some of the terms you hear in identifying plants:

http://www.clemson.edu/extfor/publications/bul117/characteristics.htm

Here is a link that might be useful: {{gwi:288209}}

A leaf scar is the mark left on the twig when the leaf falls off in autumn. You can use leaf scars to identify woody plants in the winter when there are no leaves, if you're really into it. Unfortunately, in the summer it's hard to see them because the current crop of leaves hides them. You might be able to find a dead twig that has some recognizable leaf scars. In a few cases, and this is one of them, a characteristic of the leaf scar, ie the little fuzzy 'mustache' on the top, is one of the most reliable ways to tell two species apart (the really easy way to tell these two apart is the fruit, but you haven't always got fruit.)

Anyway, here's a pdf that has information about telling Butternut and Walnut apart; scroll down a couple pages. I couldn't find any really clear pics on the web in a quick search. I think I've seen the end leaflet/no end leaflet used to tell them apart, but it's not real reliable.

WW

Here is a link that might be useful: Telling Butternut and Walnut apart.

The tree pics posted are black walnut for sure. Black walnut has deeply furrowed bark, whereas butternut has much shallower furrows and a smoother appearance to the bark (see pic). Immature black walnut fruit sometime has that little "tail", so I'm sure that is black walnut. Butternut fruit is very elongated, no roundess to it at all. Both nut trees have that citrusy fragrance to their fruit and leaves/young twigs. Be careful, the pulp that surrounds the nut stains very readily - looks like and stains like iodine.

Here is a link that might be useful: Butternut mature bark