\u00a9 2020 wikiHow, Inc. All rights reserved. Walnut tree bark: The black walnut tree has dark gray to brown bark with deep ridges in diamond shapes. This image is not<\/b> licensed under the Creative Commons license applied to text content and some other images posted to the wikiHow website. The black walnut tree is native to the eastern United States. In the dead of winter when both foliage and fruits are absent or buried under snow, the black walnut tree still can be identified. You can usually find them in forests stretching from the east coast of the United States to the Midwest. wikiHow, Inc. is the copyright holder of this image under U.S. and international copyright laws.