All over California right now, tree trunks are being mechanically shaken so hard that nuts rain down everywhere.  Almonds and walnuts are shaken onto the ground by metal claws attached to a hydraulic arm attached to a tractor.  They are then pushed into windrows by a machine that uses a combination of brushes and blowers.  Finally, the long piles of nuts are vacuumed up by a third machine that spits out leaves and sticks before depositing them in a large hopper.
Pistachios are also shaken off the trees, but not onto the ground.  The nuts so small that they would get lost in the cracks and crevices in the soil.  But even more problematic is that the shells actually split open while the nuts are still on the trees.  Letting them fall on the ground would expose them to far too much dirt and other potential contaminants.
To harvest pistachios, farmers use a pair of machines originally designed to harvest prunes.  The machines are designed to operate together, each one moving along one side of the tree row, facing the other machine on the other side of the row.  Both machines have angled tarps that extend out to catch the nuts falling from both sides of the tree.  One half of the pair has a shaker arm that reaches out, grabs the tree and shakes it.  The nuts fall onto the tarps and slide down onto a long conveyor belt on the second machine that moves the nuts backwards into a bin.
Nut harvest is a dusty, noisy and somewhat violet practice — shaking the trees causes the ground to shake as far as a hundred feet away.  And while it takes longer to harvest pistachios than almonds or walnuts, it’s still a far faster process than harvesting a tree crop like peaches.  Just two or three people can harvest hundreds of acres over the two months or so the season lasts.
But it will soon get even faster.  The orderly nature of a nut orchard — straight rows of trees planted at regular intervals — lends itself naturally to automation.  When people think of robots in agriculture, they often imagine robots trying to harvest tomatoes or strawberries.  But the first robots you’re likely to see on farms will be nut tree shakers.
Mechanization can speed up the harvest, but it can’t speed up the ripening of the nuts.  Unripe pistachios won’t fall off the trees no matter how hard you shake them. This year’s harvest turned into a bit of a nailbiter for us, as we finished up on Monday of this week — a month later than usual and the first time anyone can remember in October.  One day later and the rain would have knocked lots of nuts on the ground, rendering them useless.
To celebrate this year’s harvest, we’ve sent along a bag of pistachios in your boxes today.  Enjoy!