Hi, I'm contemplating converting about 40 acres of cropland to a Black Walnut forest/orchard. As part of my contemplation & planning, I'd like to have an idea of the growth rate I could expect for the trees (DBH, not height). Are there charts or tables available that might show what "typical" growth rates might be based on some inputs, such as tree spacing, plant hardiness zone, average rainfall & sunlight, etc.? I understand that it's impossible to predict the exact DBH of any tree 10, 15, or 20 years into the future, but I'm hoping that someone might have collected some data along the way that could help guide me. As part of my evaluation for converting this cropland, I'd like to know if my trees might reach 20" DBH in, say, 15 years, 20 years, 30 years...? This would help in financial planning for things like expenses of thinning of the forest/orchard, possible revenue from the lumber, etc. Also, do you know if similar information might available for nut production based on the year of age of the tree(s)?

Hi Jon:

As expected, there is quite a disparity in black walnut (Juglans nigra) growth and yield data based on numerous factors such as soils/site, initial spacing, weed control, maintenance, thinning, etc.

Just to let you know, it will take at least 45-60 years to grow eastern black walnut trees to 20" dbh – and that’s on a good site with plenty of management. One of the biggest illusions or lies on the internet is that one can get rich within 20-30 years by planting, growing, and selling black walnut trees. If only it were that easy!

Here is a URL to data from Indiana and Illinois highlighting annual diameter increment of various hardwood species, including eastern black walnut: https://www.nrs.fs.fed.us/pubs/rp/rp_nc257.pdf

“Black walnut is one of the more rapid growing hardwoods. On good sites young trees may grow 3 to 4 feet in height per year, and in 20 years may attain heights of 40 to 50 feet with diameters of 6 to 10 inches. Because it responds well to management, growth of immature trees can often be more than doubled by weed control, thinning, and other cultural practices.” Source: https://www.fpl.fs.fed.us/documnts/usda/amwood/270bwaln.pdf

“Although the empirical data from this study was obtained from a relatively small sample of black walnut trees, and the individual site data could not be reliably combined or statistically compared, the data indicates that an average annual DBH growth increment of one-fourth (0.25) to one-third (0.33) inches per year [0.241” – 0.342”; ave: 0.293”] can be conservatively projected for black walnut trees in southeast Nebraska (Table 1). Optimum growth of black walnut trees is a function of multiple factors, including climate (i.e., precipitation, temperature, wind, etc.), site characteristics (i.e., soil texture, fertility, depth, pH, etc.), and silvicultural management regime (i.e., stocking, thinning, weeding, etc.).” Source: https://nfs.unl.edu/documents/ruralforestry/BlackWalnutTechReport.pdf

Additional Information on Planting, Growing, and Tending Black Walnut:

Center for Agroforestry’s Black Walnut Financial Model 2.0 http://128.206.25.160/profit/walnutfinancialmodel.php

Manager’s Handbook for Black Walnut https://www.nrs.fs.fed.us/pubs/gtr/gtr_nc038.pdf

Here is some good information on growth eastern black walnut for nut production: https://centerforagroforestry.org/wp-content/uploads/2021/05/af1011.pdf

Best of luck!