Controls on vegetable growth, flowering, and production of Hops in the Southeastern USA

View the project final report

Commodities

• Agronomic: hops

Practices

• Education and Training: farmer to farmer, on-farm/ranch research
• Production Systems: general crop production
• Soil Management: soil analysis
• Sustainable Communities: infrastructure analysis, new business opportunities

We applied several treatments to Cascade hops at Kelly Ridge Farms' hop yard (Meadowview, VA) in an attempt to affect vegetative growth and infloration timing.  These variables can directly control hop cone production per crown which is of critical interest to this industry.  Applied treatments included techniques to increase early soil temperatures, three different timings of early emergent shoot pruning, and two apical meristem manipulation treatments.  We attempted to survey regional growers for additional data and engaged local college students in the experimental process.  Our results were presented at meetings of regional hops growers and at the Association for Southeastern Biologist 2016 meeting.

Introduction

The bulk of America's production of Hops (Humulus lupulus) has historically been limited to the Pacific Northwest. Several recent economic and cultural factors have conspired to spur an interest by the farming community in regional production of the crop: the recent explosion of the craft brewing industry; local-vore movements that encourage sourcing ingredients within a narrowly defined geographic area; and the environmental, financial, and regulatory considerations of shipping and preserving unwieldy amounts of vegetative material intended for consumption.

A major hurdle to production in the Southeastern United States is lower overall production per acre compared to that of traditional production areas. Virginia growers have estimated current average production per acre at about 25% of larger Western producers. The ability to achieve an adequate amount of vegetative growth prior to flowering is hypothesized to be a significant variable in this production gap.

There is significant economic incentive to solve this problem of yield. Locally sourced hops allow consumers to experience wet-hopped beers - a popular style that has been prohibitively difficult to procure for brewers that are separated by a distance threshold from established large producers. Brewers are able to have more quality control of their ingredients, as well as a line of communication for input with growers. Locally-sourced hops also reduce the additional costs and the increased carbon footprints associated with transcontinental shipping.  

Flowering in Humulus lupulus is controlled by a complex interrelationship of light, temperature, vegetative size requirements, and hormones. Hops require a vernalization period of approximately six weeks. It is a photoperiod sensitive plant which has been described as performing best between 35 and 55 degrees latitude; this is due to longer summer day lengths, which extend the vegetative growth that ultimately provides the platform for flower growth. Previous research indicates that the short day lengths and minimum internodal numbers/lengths (i.e. vegetative growth) that occur in autumn incur flowering. Increasing the period of vegetative growth and delaying the final flowering stage results in an overall increase of commercially viable yield.  Manipulation of these variables could also potentially contribute to affecting local flavor and characteristic/chemical variations contributing to a regional “terroir”. 

Several treatments for affecting these variables have been hypothesized.  Hop growers in South Africa have reportedly had success using phototherapy to delay hops flowering and increase production.  There is also anecdotal evidence that several Virginia growers have experimented with pruning treatments to delay flowering.  Plant hormones which control flowering are typically produced in the apical meristem (the tip of the hop bine). The removal or manipulation (inverting) of the apical meristem may favorably affect hormone concentrations and delay associated flowering. However, these experiments have yet to be performed with scientific rigor or to be adequately documented.

Region-specific research into sustainable and responsible manipulation of these and other variables could potentially narrow the production gap between eastern and western growers.  Theoretical successes may even allow a southward expansion of hops production into traditionally unfavorable areas (lower latitudes with shorter summer day lengths).  Such innovation could open up new viable crop options to southern farmers.

We evaluated three potential treatment types (a total of 7 discrete treatments) to affect vegetative growth and associated flowering timing in Cascade hops.  These were all designed to attempt to increase the amount of vegetative growth prior to flowering, either through promoting earlier vegetative growth or delaying the onset of flowering.  This was hypothesized to result in increased hop cone production.  Environmental, vegetative growth, hops cone production, and hop cone analytical data was collected to evaluate these treatments.  

We attempted to gather and document production data via questionnaires from regional growers regarding observed flowering and emergent shoot timing through the established regional growers organization Old Dominion Hops Cooperative.

We presented our results at two quarterly growers meetings of the Old Dominion Hops Cooperative in Charlottesville, VA. 

Our results were also presented by Emory and Henry Cooperators at the Association for Southeastern Biologists annual meeting in Concord, NC on March 31st – April 3rd, 2016

Students from Emory and Henry College (Primarily Emily Belanger) participated in research implementation activities throughout the summer collecting data and evaluating results, receiving an unique learning opportunity.