black walnut (Juglans nigra)
Juglandaceae, the walnut family
How to recognize black walnut. Look for large, alternately arranged, pinnately compound leaves with leaflets numbering 11-23 (or an even number, 10-22, as the terminal leaflet is often reduced or missing).

Black walnut in mid-June with immature fruits..
Flower and fruits. Like many forest trees, black walnut is monoecious, producing separate wind-pollinated pollen-producing (male) and ovule-producing (female) flowers on the same tree. The males are small and very numerous, borne in drooping elongate catkins, whereas the females are larger and occur in few-flowered clusters.

Black walnut flowers, males on the left, females on the right.
Walnut fruits are large “drupes,” i.e., single-seeded , surrounded by a fleshy non-splitting husk. Here’s what the walnuts look like after they’re fallen on the ground.
In the winter. Black walnut twigs are stout, with three-lobed leaf scars fancifully resembling monkey faces., and a true terminal but. Inside, they have beautiful chambered pith.

Black walnut twigs have a true terminal but, monkey-face leaf scars, and chambered pith.
Where to find black walnut. E. Lucy Braun, in The Woody Plants of Ohio (1961, 1989; The Ohio State University Press) tell us that this species “is “A tree of rich soil, almost always present in mixed mesophytic forest communities and frequent on high-level bottomlands.”
Scanned Image from an Old Book
(Flora of West Virginia, by P.D. Strausbaugh and Earl L. Core)

Oooh ooh. I have a question!
Why do gardeners recommend against planting veggies near a walnut tree?
Black walnut is often cited as being “allelopathic,” (literally meaning to make your neighbor sick). This an effect wherein the roots, leaves and fallen fruits produce a chemical –Juglone –that inhibits the growth of some plants, especially members of the tomato family. Allelopathy is seen as a means to minimize competition from other plants.