General Information
Hop is a specialty crop produced for the female flowers, or cones, which either raw or processed, are an essential ingredient in the production of beer. Lupulin glands on the hop cones contain soft resins (a and b acids) essential oils that impart bitterness, flavor, aroma, foam (head) characteristics, and preservative qualities to beer. The total amount and percentage composition of these compounds varies with variety and growing conditions. Because the brewing industry depends on hops to provide distinctive and proprietary characteristics to beer, a stable supply of high quality hops is a high priority.

Idaho ranks third in U.S. hop production accounting for 8% to 10% of the U.S., and 2% of the world hop production. Idaho hop production from 1993 to 1996 averaged 1,388 pounds per acre on 3,977 acres. Total production for that period averaged 5,521,210 million pounds with an on-farm value of $8,889,148 million dollars, annually. In 1998, production dropped well below that average to 4,529,000 pounds on 3,909 acres with a total farm-gate value of $6,838,394.

Over 90% of the crop is generally contracted at the time of harvest. Some contracts prohibit the use of certain pesticides on the contracted crop, in order to meet specific brewing industry requirements or to comply with the import tolerance requirements of importing countries. In a given year 40% to 60% of the crop is exported to overseas markets. (back to top).

Idaho Production Regions
Hop production in Idaho is concentrated in two geographically distinct areas: the cool, moist region of the northern Idaho panhandle in Boundary County and the warmer, arid region of southwestern Idaho in Canyon County. Climate, soil type, hop varieties, and therefore, hop production practices, vary greatly between these two areas. (back to top).

Cultural Practices
Hop plants are grown on a wire and cable trellis suspended about 18 feet above the ground on a regular arrangement of poles. Cement anchors, attached to trellis cables and buried five feet deep, surround the yard and hold the trellis upright under the weight of the developing crop. Plant spacing is either wide, with 14 to 15 feet between rows and 3.75 feet between plants with in rows, or narrow, with plants set 7.5 feet apart on a regular grid. With either planting arrangement there are approximately 55 poles and 900 plants per acre. Once established, the hop rootstock will produce indefinitely although industry practice is to rotate plantings every 10-15 years. Timing of rootstock replacement is influenced by declining yield caused by insect and disease and pests and by brewer demand for specific varieties. The major cultural practices used annually to produce hops include pruning, stringing, training, irrigating, and harvesting. Each of these is discussed below. (back to top).

Pruning is an annual spring practice used to hold back the vigorous new annual growth until the proper training date for that variety. Pruning begins in late March and is accomplished either mechanically or chemically. Mechanical pruning uses tractor-drawn equipment with spinning steel "fingers," to remove early vine growth, debris from the prior season, and leave a clean, surface from which the new shoots will arise. Chemical pruning involves the use of desiccants to kill back early vine growth. Fields pruned chemically are often 'scratched' with a harrow to remove surface debris. (back to top).

Stringing the trellises begins in early April as seven-man crews using tractor-drawn elevated platforms tie the coir (coconut husk fiber) twine to overhead trellis wires and secure the lower end of the twine into the hop crowns with small metal clips. (back to top).

Training is the practice of wrapping the hop shoot in a clockwise direction around the stringing twine to facilitate rapid vine growth. Training begins in early May and is by the end of May. Due to the relationship between plant height and day length that determines flowering time, the training date is one of the most critical factors in determining yield. Training date is variety specific. Hop vines (or bines) in narrow spaced fields must be tied together, or arched, 6 ft. to 8 ft. above the ground in late spring to facilitate crop management activities. (back to top).

Irrigation of hop fields begins in the latter part of May or early June, depending on weather and growing area. The hop field will require approximately 30 inches of water during a normal growing season. Various methods of irrigation are utilized, including rill, sprinkler and drip. In Idaho most irrigation is by rill method, where water is siphoned out of head ditches into smaller ditches (rills) alongside the rows of hop plants. (back to top).

Harvest begins in late- August, and progresses through late-September with each variety reaching peak maturity at a different time. Harvest begins in the field as the hop vines are cut at the ground and at the overhead support wires, and are placed into a trailer or truck bed. The vines are transported to stationary picking machines that are capable of picking 8 acres in a single 10-12 hour shift or 15 acres if picking runs round the clock. Most U.S. hop growing operations have one picking machine for each 250-300 acres of hops. (back to top).
The vines are hung upside down on hooks and carried into the picking machine, where hops and leaves are stripped from the vine and sent through a series of cleaning devices to remove leaves and other debris. The stripped vines and other debris are chopped and spread back onto the fields and service roads. To date, this activity has not resulted in the build up of disease or insect pest in hop yards. The introduction of hop powdery mildew into the Pacific Northwest may force growers to change this practice. Powdery mildew cleistothecia (spores from sexual reproduction between two different mating types) can exist on dead plant debris. If powdery mildew cleistothecia become common other methods for disposing of plant debris may need to be found. (back to top).

Drying & baling begins when cleaned cones are transported by conveyor belt to the hop kilns. Kiln floors are each approximately 32' x 32', and hold some 15,000 pounds of hop cones. Cones are spread to a depth of about 32 inches. Once the kiln is filled, cones are dried as hot air (140°F) from oil or gas burners is forced through the bed of green hops. The drying process requires about 9 hours, reducing the hops to 30% of the green weight, with 8-10% moisture content. Hops are removed from the kiln floor and cooled for 24 hours. After cooling, the hops are compressed into 200-pound bales, wrapped in burlap, subjected to quality inspection, and transported to cold storage warehouses.