Nut Size Nut size will vary with the variety, age of tree, size of the crop and moisture conditions during the growing season until shell hardening. Most trees will start to produce pecans within five to eight years depending on variety, growth rate and location. Many pecan trees are alternate bearing, they produce a large crop one year and a smaller crop the next. For home harvesting, gathering falling nuts can be an option, but you usually have to fight the squirrels, who are master nut gatherers. Small harvests can be achieved by tapping limbs with a padded stick to help with nut drop, or commercially tree shakers are used.
Mechanical shakers are fascinating to watch.
Once secured on the trunk of the tree, they are turned on and the tree shakes rapidly, causing the nuts to drop like pelting rain. Standing nearby, even the soil vibrates. Then the nuts are gathered, removed from their outer husks and sorted. Pecan nuts lose quality very quickly on the ground, especially during wet weather, so it is important to harvest soon after shaking. Fresh pecans need to be air dried for two to three weeks before storing.