Hops are the small, cone-shaped flowers of the female Humulus lupulus plant, a climbing perennial vine grown on trellises. These flowers are indispensable to brewing, where they impart bitterness, flavor, and aroma to beer. The process of harvesting hops requires highly specialized agricultural machinery and meticulous timing to ensure the delicate cones retain their maximum quality and brewing potential. The entire system is built for speed, moving the harvested material quickly from the field to the drying facility to stabilize the product.
Determining the Optimal Time for Harvest
The window for hop harvest in the Northern Hemisphere typically opens in late August and extends through early October. Determining the exact harvest date is crucial, as picking too early or too late compromises the concentration of desired compounds like alpha acids and essential oils. Growers aim for a specific moisture content, targeting harvest when the cones have dried naturally on the bine.
Experienced hop farmers use sensory cues in addition to scientific testing to confirm readiness. A mature hop cone should feel dry and papery, springing back immediately after a light squeeze. When shaken, the cone should produce a slight rattling sound, and the sticky, yellow lupulin glands inside should be visible and highly aromatic.
Bringing the Bines Down
The hop plant, known as a bine, is trained to climb support strings that stretch from the ground up to a tall trellis system. The physical harvest begins with specialized field equipment designed to handle the plant’s height. A tractor-driven machine called a bottomcutter first severs the bine a few feet above the ground to protect the root crown for future seasons.
Immediately following this, a topcutter travels along the trellis, slicing the bine from the support wire at the peak of its climb. This coordinated effort causes the entire, intact bine—a long length of vine, leaves, and cones—to fall directly into the bed of a waiting hop truck. The bines are then transported from the field to the processing facility, often called the picking shed or hop kiln.
Separating Cones from Plant Matter
Once the full bines arrive at the processing facility, they are fed into the hop-picking machine. Workers hang the bines onto conveyor chains that pull them up and into the machine. Inside, a system of rotating metal arms, wire teeth, or flexible fingers strips the hop cones, leaves, and lateral branches from the main stem.
The resulting mixture of cones and unwanted plant material, known as chaff, then moves through a series of separation stages. Large blowers and fans apply streams of air to lift and carry away the lighter leaf material and stem fragments. The heavier cones drop onto a series of sifting screens and dribble belts, which further isolate the cones from any remaining extraneous matter, ensuring a clean product moves to the next stage.
Kilning and Preparing Hops for Storage
Freshly picked hops contain a high moisture level, which makes them susceptible to rapid spoilage. To stabilize the crop for long-term storage, the cones must undergo a controlled drying process called kilning. Hops are spread in deep layers on a perforated floor inside a kiln.
Forced hot air, with regulated temperatures, is pushed up through the bed of cones. This careful temperature control reduces the moisture content without evaporating the volatile essential oils and resins, such as lupulin, which provide the hop’s brewing value. The goal is to reduce the moisture level down to a stable range of 8–12%. Once dried, the hops are moved to a cooling area to allow the residual moisture within the cones to equalize. Finally, the dried, cooled hops are compressed by hydraulic balers into dense, square bales for efficient storage and shipment to brewers worldwide.