By Malinda Geisler, content specialist, Ag Marketing Resource Center, Iowa State University.
Revised April 2012.
The black walnut tree, also known as the American walnut, is native to North America. The Northern California black walnut is primarily used as the rootstock for English walnut cultivars.
According to the National Resources Conservation Service, black walnut thrives in deeper, well-drained, neutral soils. It must have direct sunlight and requires about 35 inches of annual precipitation. The tree usually matures in about 150 years. An average tree will grow to 70 to 80 feet in height and a diameter of two to four feet. In addition to producing nuts, the tree produces wood that is used for furniture veneer.
No USDA statistics are kept on black walnut production. Black walnut hulls need to be removed as soon as the nuts fall from the trees. For small amounts, walnuts can be spread out on a gravel driveway and driven over for about one week. A hand-operated corn sheller can be used to remove walnut hulls. In larger operations, mechanical devices are used. After the hull/husk is removed, the nuts need to be dried for at least two months in a place with good air circulation.
Black Walnut, Virginia Tech, 2001 - This online document provides a review of the harvesting, processing, marketing and usage of black walnuts.
Walnuts: Second Biggest Nut Crop Produced in the United States, Fruit and Tree Nuts Outlook, Economic Research Service, USDA, 2005.
- Black Walnut Financial Model (Version 2.0), University of Missouri Center for Agroforestry - This Excel spreadsheet was developed to assist potential growers with decisions on tree spacing, nut harvest and whether to use improved or unimproved trees.
- Black Walnut Plantation Management, Purdue University Cooperative Extension Service, 1994 - This online manual outlines black walnut plantation establishment and management.
- Center for Agroforestry, University of Missouri - This center is a national leader in the development of specialty crops for alternative income sources on family farms, including black walnut.
- Experts on Black Walnuts, Northern Nut Growers Association, Inc. - Experts on black walnuts may be located by selecting the black walnut box on this link.
- Growing Black Walnut, University of Minnesota Extension Service - This bulletin offers sound research with practical applications for black walnut tree growers.
- Growing Black Walnuts for Nut Production, Center for Agroforestry, University of Missouri, 2007.
- Growing & Processing Black Walnuts, Tom Clothier's Garden Walk & Talk - This site offers instructions for harvesting and extracting nutmeats for home consumption.
- Hammons Products Company, Stockton, Missouri, 1-888-429-6887 - This company, which buys hulled black walnuts, has 220 buying stations in the Midwest. In 2009, the company processed 16 million pounds of black walnuts, down from 38 million pounds in 2008.
- Heartland Nuts 'N More, Valparaiso, Nebraska - This cooperative of 44 native black walnut and pecan growers from Nebraska, Iowa, Missouri and Kansas. Founded in late 2003, the co-op purchases products from its members, then processes and bags the nuts to be sold nationwide.
- Introduction to Walnuts, Pecans and Other Nut Crops, Specialty Crops Profile, Virginia Cooperative Extension.
- Nut Production Handbook for Eastern Black Walnuts, Forest Service, USDA, 1998 - This publication is specifically for the commercial production of Eastern Black Walnuts.
- Walnut, Integrated Pest Management guidelines, University of California, Davis.
- Walnut Council - This association helps build markets for wood products and nut crops.
- Walnut Index, University of California-Davis - This site provides links to other walnut resources.
- The Walnut Tree: Allelopathic Effects and Tolerant Plants, Virginia Cooperative Extension - This online document reviews unique characteristics of black walnut trees.
- Why You Should Worry about Your Walnuts, Iowa State University Extension, 2009 - Thousand cankers disease is a malady looming on the western horizon that has already claimed many Eastern Black Walnut trees transplanted to the western states.
Links checked April 2012.