The commercially valuable Persian walnut, also called English walnut(J. regia),along with several closely related species or geographical variants, compose the last group, section juglans. This group is characterized by four-chambered nuts with hulls that dehisce and separate from the shells at maturity.
The Persian walnut appears to have evolved in the mountain chains of central Asia, which extend from turkey to iran through southern portions of what used to be the USSR to western china and the eastern Himalayas.
The harvesting season can begin as early as September and run through the end of November. The walnuts are ready for harvesting when the outer green husk enclosing the walnut fruit begins to split. Walnuts are cleared from the orchard floors and mechanical shakers come in to collect the nuts from the trees. Any remaining husks are completely removed, revealing the walnut’s wrinkly shell. The walnuts are then dried, cleaned, and packed for sale as “in-shell” walnuts, or moved to the hulling process to be deshelled. After the hulls are removed, the walnuts are further sorted by size.