In the Walnut family, it is the English Walnut that is most desirable for the home landscape. As an ornamental feature for a residential yard, the Black Walnut tree has a lot of liabilities. It is not especially attractive. Its foliage is slow to appear in spring and quick to drop in the fall and has little color. It tends to be messy, dropping its hard nuts all over the lawn, and possibly on people's heads. Any green, immature nuts crushed by the car exude a yellowish juice celebrated for its use as a black dye.
Another drawback to Black Walnut trees is their documented toxic effect on certain neighboring plants. The English Walnut and the Butternut produce a similar toxic material (juglone) but not in such great quantities. Nearby apple trees, rhododendron, azalea, laurel, blueberries, pines, hemlocks, arborvitae, sweet gum, American holly, black ash, tomatoes, and potatoes are known to be poisoned by Black Walnut neighbors. In light of all this, the best use of Black Walnut trees, if a person insists on planting them for reasons other than nut production, is in naturalized or wooded areas on the property where they can have lots of light and space. They look good in rows along property lines and as individual specimen trees in spacious yards, their liabilities notwithstanding.
If you wish to produce some nuts along with having a lovely shade tree, Walnut trees usually take from 5 to 8 years before you start seeing any nut crop. The biggest problem when there are only one or two trees is that the squirrels will consider those nuts as their sacred lunch and will usually wipe out the crop while the husks are still green.