"Black Walnut" - Juglans nigra

Meet the "Black Walnut" - Juglans nigra

The Black Walnut - Juglans nigra - is a large flowering deciduous tree in the Walnut family, growing to heights of 100-130+ feet tall.  The bark is a grey-black color that shows deep furrows throughout.  The leaves are green during the growing season and are made up of 15-23 leaflets growing in an alternate pattern, chaging in color to a bright yellow in the fall.  

Image Citations: (Photo #1) Bill Cook, Michigan State University, Bugwood.org (Photo #2) Paul Wray, Iowa State University, Bugwood.org 

The roots of  the Black Walnut produce a chemical called Juglone (5-hydroxy-alphanapthaquinone), this chemical is known to be harmful or toxic to many other plants and some animals. most notably horses.  Horses are effected most when Black Walnut wood chips or sawdust are used in their bedding, exhibiting allergy symptoms (which are worse in the spring) similar to that of humans.  Plants including tomatoes, potatoes, blackberries, blueberries, azaleas, mountain laurels, rhododendrons, red pines and apples are known to be severly injured if not killed when planted/grown in 50-60 foot of the Black Walnut. Gardeners should take care when planning a garden around a mature Black Walnut, paying extra attention to what plants are tolerant of Juglone.  

The Black Walnut is native to the Mid-West and Eastern-Central United States, with a recommended growth zone of 4-9.  This tree is used in both nut and lumber production.  The trees begin to produce nuts at 4-7 years old and continue annually ripening each October, because it is self pollinating it is possible to have nuts with just one tree.  The nut is firm and has an enjoyable flavor.

Image Citation (Photo #3): USDA Forest Service - Northeastern Area Archive, USDA Forest Service, Bugwood.org 

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