Maximum Yield USA June/July 2019 | Page 36

VARIETIES There are a number of modern commercial varieties of hops bred for specific uses, as well as many older, general purpose heirloom types. Popular varieties include Cascade, Chinook, Columbus, Magnum, and Centennial, each with different compositional qualities. Research into hydroponic hops has shown that Cascade and Chinook are suitable varieties for small-scale hydroponic production and perform well under greenhouse production. The Cascade variety is the most widely utilized by craft brewers in the US and is used in the production of many types of ale and some lagers. With a high alpha acid content (4.5-6 per cent) and a pleasant citrus like aromatic quality, Cascade is a general-purpose hop variety well suited to hydroponic production GROWING Hop cones are produced on long bines (vine-like stems) which support the plant by clinging to support structures. Greenhouse-grown hops may be grown for year round production of `wet hops’ for the craft beer industry. Young hop shoots produced by an underground rhizome system which is used for propagation. 36 Maximum Yield Hops are relatively easy to grow as they are extremely vigor- ous and heavy feeders that benefit from the controlled nutri- tion of hydroponic systems. Hops produce separate male and female plants, with only the female plants producing cones, thus hop propagation is typically carried out vegetatively to ensure only female plants are grown. If male flowers are present in a hop crop, the pollination of the female flowers results in seeds that are undesirable for brewing beer. For small-scale growers, hops are typically obtained during the dormant winter season as short sections of rhizome containing a number of dormant buds. Once planted into warm conditions, rhizomes establish quickly and produce several young shoots. Hop cuttings can also be taken from established plants that will produce roots readily at leaf nodes without the requirement for any rooting hormone application. At certain times of the year, young potted hop plants are available for purchase. Once growth has begun, the hops produce long, climbing shoots called bines that develop short, stiff hairs along the stem surface, allow- ing the bine to cling and climb upwards (vines on the other hand, use tendrils or other means to cling to surfaces). This rapid upward growth of the bines requires support, and hydroponic hops are well-suited to being grown on train- ing systems similar to those used for tomato and cucum- ber crops. Tomahook tomato support systems — overhead wires with strings or trellis — may be used to support hops and plants will readily climb and cling with no assistance. Since hop plant bines grow to considerable length and height, for indoor and greenhouse production the “lean and lower” system of training, commonly used for commercial tomato crops, appears to work well. As the bines increase in height, the supporting string is detached and lowered along the floor or lower levels of the cropping area as required. Alternatively, the tops of the bines can be trained verti- cally along supports at the top of crop, or allowed to grow upwards, and then trail back down towards the floor. As with other larger hydroponic plants, hops are best grown in a drip-irrigated system with at least two gallons of a free draining growing substrate, such as perlite or coarser grade coconut fiber, as they are intolerant of wet feet, particularly in the early stages of growth. Nutrients should initially start with a high-quality, general purpose vegetative formulation at an EC of 1.8–2.2 with a high ratio of nitrogen to potassium. During the later stages of growth, this can be switched to a flower- ing/fruiting formation with higher potassium and phosphorus levels, as well as gradually increasing the EC during the cone production stage to maintain high levels of essential oils and other compounds that constitute the quality of the flowers.