Ash trees belong to the Fraxinus species and grow commonly in cities and forests. The bark is usually dark gray to black. Black walnuts look like green balls on the tree – … If you really can’t stand to see another ad again, then please consider supporting our work with a contribution to wikiHow. Black walnut trees (Juglan nigra) are found throughout much of the central-eastern part of the U.S., except in the far northern and far southern part of this range, but familiar elsewhere from the East Coast into the central plains. Be careful when using a knife. Black walnut trees are odd in that they are safe for all livestock except horses, and horses are generally only affected by shavings made from the tree. Best of all are the twigs and buds. The site looks at walnut trees sold for timber purposes, rather than those sold for garden purposes. However, different veneer markets have different requirements. This image may not be used by other entities without the express written consent of wikiHow, Inc.