Black Walnut

Juglans nigra

Black walnut reach about 75’ x 60’ in size with a round to oval shape. This tree can be a fast growing tree when young with adequate watering, but typically is a slow growing tree as it matures. It has alternate, odd pinnatley compound leaves with 15-23 leaflets. They do very well in most soils and prefer full sun. They do not do well along streets or in compacted soils.

It produces commercially important nuts and the wood is highly sought for fine furniture and veneers. If you don’t mind the mess they are excellent landscape trees.

Formerly an excellent shade tree choice, caution should now be observed before planting this species because of the high susceptibility to Thousand Cankers Disease.

Common Problems

Environmental

Leaf Scorch is an issue when temperature are hot and there is not adequate soil moisture.

Diseases

The major disease to watch for in black walnuts is Thousand Cankers Disease. Please read about it in the “Tree Problems” section if you are considering planting a black walnut or already have one on your property.

Powdery Mildew can also be an issue if the spring is cool and wet. Other canker causing diseases and twig blights occur, but are less common along the front range.

Pests

Aphids are a very common nuisance among Colorado black walnuts. The walnut twig borer is a major player in Thousand Cankers Disease and trees should be closely monitored for them.

Cultivars

There are many cultivars and varieties of walnut.

History and Use

Black walnuts have a very rich history as shade trees, food producers and providers of beautiful wood used for furniture, veneers, instrument building and more. Very common street tree. Wood can be used in furniture and flooring.