Photos were taken from an ongoing prunning trial in Colusa County.
Lampinen, Bruce, John Edstrom, Samuel Metcalf, William L. Stewart, Claudia Negrón and Loreto Contador. 2015. Howard walnut trees can be brought into bearing without annual pruning. California Agriculture, April-June online Vol. 69:2 (http://californiaagriculture.ucanr.org/landingpage.cfm?article=ca.E.v069n02p123&fulltext=yes) .
Negron, Claudia, Loreto Contador, Bruce D. Lampinen, Samuel G. Metcalf, Yann Guedon, Evelyne Costes, and Theodore M. DeJong. 2014. How different pruning severities alter shoot structure: a modelling approach in young ‘Nonpareil’ almond trees. Functional Plant Biology 42: 325-335.