Black walnut poses some problems when used in urban landscapes. Although it is long-lived, grows quickly and provides a light, dappled shade, it is prone to wind breakage, and the nuts can be quite a nuisance. The roots of Black Walnut (Juglans nigra L.) and Butternut (Juglans cinerea L.) produce a substance known as juglone (5-hydroxy-alphanapthaquinone), that inhibits the growth of many adjacent plants, [3] including Scots Pine, Birch, Basswood, apple trees, grapes, and hydrangea. This herbicide is contained in the tree's roots, leaves and nut husks, and the residue remains in the soil for years even after the tree has been removed. However, there are plants admirably resistant to juglone, and they can be grown reliably even underneath this hardy tree.

Click here for a site from Ohio State University listing plants immune to the Black Walnut's toxin.

Walnut wood is used for veneer in paneling, doors, furniture and cabinets, and sawn into tool handles and gunstocks. Black walnut is one of six walnut species found in North America. There are 15 described species worldwide. Although black walnut grows throughout The United States and southern Canada, it is most common in the U.S. midwest and east. Black walnut is a pioneer species, and is often the first colonizer of disturbed sites and farm fields gone fallow. It grows best in deep, moist soil found in river bottomlands. The tree tolerates periodic flooding found in such locations, but is shade intolerant. In natural woodlands, it is most often found in small groupings or scattered specimens in forest openings.

Black walnut wood is so valuable, poachers have been known to steal trees from public lands or private landowners. In one such case in Indiana in 2004, Purdue University scientists were able to use DNA analysis to match wood from illegally-felled tree stumps with logs confiscated at a sawmill 60 miles away. [2]