Originally Persian in origin, the English walnut tree, bearing the round tan walnuts found commercially, takes five to seven years to develop into a mature tree suitable for harvesting. The stately shade tree reaches to about 60 feet in height and must be shaken to yield its shelled treasures. Harvesting may begin as early as August when the hull inside the shell loosens or bursts and turns brown. Harvest English walnuts as soon as they show signs of maturity: delaying harvest could result in darkened kernels and mould growth.
Determine whether the English walnuts are ready for harvest. Make sure three conditions are met: the nuts are fully mature and non-green tasting, 99 per cent of the nuts can be shaken from the tree in a 15 second attempt at shaking without damaging the tree and 98 per cent of the nuts that fall to the ground can be hulled without damaging the shell or containing any green hull.
Produce conditions favourable for harvesting. The above conditions may not coincide, in which case you may encourage them by curbing water irrigation and controlling dust and ripening. Light rain and heavy dew can be especially welcome during harvest time, as this can help the hulls to split naturally.
Test to see when to begin harvesting. Do this by taking a pocket knife and driving it 1 inch into the English walnut at the attachment point. Give it a 90 degree twist and look for two perfect halves and a split hull that falls away by itself -- these are good indications that you can harvest within a week.
Clean and scrape the harvest floor. Prepare the ground for the walnuts that will be shaken to the ground. Scrape away all the vegetation so that the harvest floor is clean, dry and level.
Use special machinery to harvest and process the English walnuts. Shake the trees with a shaker, which will go down a row of trees to shake one pair of walnut trees: first left, then right, then it will back up and shake the next pair. Use another machine to sweep the fallen nuts away from the trees into the windrow between the rows of trees; a pickup machine will suck up the walnuts from the windrows and deposit them into carts that are taken to trucks which will send them to a huller for further processing.
Vary the shaking times. Shake the tree using the shaker for 15 seconds to loosen the walnuts or do a double shake lasting seven seconds each. Make the shaker shake at a different pattern: for example, do a four-leaf clover shaking pattern rather than a five-point star shaking pattern.