Hi Bulfrano:
Age to economic maturity is based upon several key factors: soils & site, and intermediate stand management treatments (pruning and thinning). On the highest quality sites, it would be possible to grow "some" merchantable walnut timber within 40 years; however, the most valuable trees would be required to grow 60-80 years. I don't want to burst your bubble too harshly, but I'm puzzled as to who told you that you could receive $20-25K per walnut tree at maturity? I've only heard of a dozen or so "perfect" trees that ever sold for that kind of money. $1000 walnut trees, however, are much more common in areas that grow high quality black walnut. Just remember, the key to maximizing the value of your standing trees is to MARKET them to the highest prospective buyer. Please contact your local IL Dept. of Natural Resources district forester for tree planting assistance: http://web.extension.illinois.edu/forestry/pdf/tfb-nres-201-14.pdf
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