From bine to beer.

The commercially valuable part of a hop plant is its unfertilised flowers. These are harvested by a hop grower as green seed cones that are referred to as hops or hop cones. Hop cones contain different oils, such as lupulin and oleoresin, that impart flavour and aroma to beer. Lupulin also possesses antibiotic properties that suppress bacterial growth and allow brewers yeast to grow.

Hop cones are grown on vines called bines, which are trained to grow up strings suspended from overhead trellis structure. This tall structure reduces shading and encourages increased production of the cones that grow on the bines.

New Zealand hop gardens are typically planted with a 5.0m high V-trellis structure, with rows 2.5 metres apart and plants within rows spaced at 1.2m intervals. Because pollinated seeds are undesirable for brewing beer, only female plants are grown in hop gardens, and these are propagated vegetatively or via tissue culture.

Hops are planted by a New Zealand hop grower in the spring as either rhizome cuttings or rooted cuttings from the previous spring. Hops are perennial and reach maturity in two to three years.

Each spring, rhizomes (underground horizontal stems) send up new bines that produce the cones that will be harvested late in the following summer.

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Hop quality is dependent on harvesting cones at the right time, and then picking and drying them quickly before they deteriorate. Unless they are cooled, fresh hop cones will start to deteriorate within a short period from the bines being harvested.

These time-critical requirements together with the tall growth habit of the bines mean that each garden must have its own picking and drying equipment and facilities.

The most labour-intensive tasks on an established hop garden are the stringing which takes place by a hop grower between August and early October, bine selection and training which takes place over a four week period from late October, and harvesting which takes place in March.

Different varieties of hops mature at different dates. A hop grower typically grows a range of varieties to spread the work load and risk, and make better use of harvesting equipment.

Hop bines are machine harvested and taken to an on-site picking and kiln drying building where the cones are mechanically removed from the bines and spread out to dry on a slatted floor.

Hot air is then pumped through the floor from below with the aim of, as quickly as possible, reducing cone moisture content from around 80% at harvest to around 10%.

Once dried the hops cones are heaped up to allow their dry matter content to even out, and then baled into packs similar to wool packs. A hop grower then puts these packs into cool-storage offsite, from where the dried hop cones are pelletised and packaged at a later date.