Humulus lupulus, or hops, is a long-lived, perennial, herbaceous agricultural crop commonly propagated from rhizomes and cultivated for its strobiles. The strobiles, or cone-like female inflorescences, produce a crystalline compound, lupulin, which imparts unique bittering, flavoring, and aromatic qualities to finished beer products (Almaguer et al., 2014; Burgess, 1964). Lupulin contains both alpha and beta acids, principle compounds responsible for the bittering and aromatic characteristics of hops. Alpha and beta acid concentrations are quantified postharvest and used in beer recipe design. Concentrations of these acids are largely dependent on plant age, cultivar, and environmental conditions associated with production location (Barth et al., 1994). In addition, hops contain a large diversity of volatile oils which impart a unique array of aromas described as woody, citrusy, floral, earthy, lemony, spicy, piney, fruity, or sweet (Almaguer et al., 2014). Of the vast array of volatile oils found in hops, caryophyllene, humulene, and myrcene are often regarded as the most significant and thus are conventionally reported postharvest during sale. Although considerable research has been conducted on volatile oils of hops, disagreement remains regarding the specific compounds responsible for sensory qualities in finished beer products (Goiris et al., 2014; Hofte et al., 1998; Van Opstaele et al., 2012). In addition to imparting unique bittering and aromatic qualities to finished beer products, hops confer antibacterial properties to beer, assist in sterilization and precipitation of nitrogenous compounds in wort, and act as a filtering aid in the hop back (Moritz and Morris, 1891). Diversity of hop varieties and their associated characteristics continues to foster interest in breeding and exploration for wild hop genomes (Lombard et al., 2014; Small, 1980).
Germany leads worldwide production of hops, yielding 41% of global production at 38,399,769 kg on 17,308 ha (George, 2014). The United States is the second largest global producer of hops with 34% of global production at 32,203,697 kg on an estimated 15,738 ha. Processing and production of hops within the United States is centered in the Pacific Northwest with Washington, Oregon, and Idaho being the largest producers. In 2014, Washington produced 79% of the nation’s hops on 11,678 ha averaging 2,170 kg·ha−1. Production outside of the Pacific Northwest accounts for only 2% of commercial acreage in the United States (USDA, 2015). However, interest in cultivation of hops outside of the Pacific Northwest region has continued to increase as a result of increased demand for craft beer products compounded by interest for locally sourced agricultural commodities (Tremblay and Tremblay, 2011). Although available data are limited, strobile yields from cultivation in nontraditional areas are lower than values reported for the Pacific-northwest U.S. region with dry weight of 1350, 540, 225, and 352 kg·ha−1 from ‘Cascade’ hops cultivated in New York, Michigan, Vermont, and the Appalachian Mountain region of North Carolina, respectively (Davis, 2014). In 2007, a hop shortage caused prices to rise sharply amounting to a 20% increase for commonly grown varieties and an 80% increase for specialty varieties (Welch, 2007). Record hop prices coupled with increased demand for locally produced agricultural products has led to establishment of hop production in nontraditional areas (non-Pacific northwest U.S. region). Economic analysis of small-scale (0.1 ha) hops cultivation within North Carolina indicates a breakeven-price of between $22 and $5 per kg for dry strobile yield of between 300 and 600 g/plant, respectively (Bullen and Austin, 2014). The number of craft breweries operating in the southeastern United States has increased dramatically in response to demand, with a 50% increase in Florida between 2011 and 2013 (Brewers Association, 2015). Sale of craft beer products in Florida totaled $875.8 million during 2013. Cultivation of hops within Florida or throughout much of the far southeastern United States for both local and national sale; however, has not been evaluated.
Hops require short days to flower and are primarily cultivated between 35° and 55° latitude where the plant benefits from moderate temperature and rainfall, with optimal conditions reported between 45° and 50° latitude (Hieronymus, 2012). Optimal photoperiod within this geographical range has been cited (Davis and King, 2012) as one of the most significant factors contributing to hop production success. Thomas and Schwabe (1969) examined the influence of photoperiod on hop growth and development within a controlled greenhouse environment and found inflorescence development was maximized at 16 h daylength; however, response was dependent on cultivar. Results support the optimal reported geographic range for hop cultivation between 35° and 55° latitude based on daylength; however, additional investigations are necessary to ascertain relationships between photoperiod and inflorescence development.
Germplasm obtained from plant collection efforts have resulted in commercial release of hops native to North America (H. lupulus var. neomexicanus). These varieties, native to the southwestern United States, contain unique genetic diversity not found in conventionally bred, commercially popular Eurasian varieties (Smith et al., 2006). Given their native range and unique characteristics, H. lupulus var. neomexicanus varieties may perform better in the southern United States where high temperatures are common and limited variations in seasonal photoperiod exist. The objective of this study was to examine the influence of cultivar among two U.S. native (H. lupulus var. neomexicanus) and two U.S. nonnative (H. lupulus var. lupulus) varieties on growth, quality, strobile yield, lupulin acid concentration, and volatile oil profile when cultivated in an open-sided, greenhouse in Florida. Results from this work will provide hop producers with a greater understanding of the efficacy of hop production within the nontraditional, far southeastern U.S. region. Further, differences among cultivars may establish baseline data that may be used for varietal trial experiments in future investigations.
Almaguer, C., Schönberger, C., Gastl, M., Arendt, E.K. & Becker, T. 2014 Humulus lupulus—a story that begs to be told. A review J. Inst. Brew. 120 289 314
Barth, H.J., Klinke, C. & Schmidt, C. 1994 The hop atlas: The history and geography of the cultivated plant. Joh. Barth & Sohn, Nuremberg, Germany
Brewers Association 2015 State craft beer statistics. 18 Jan. 2015. <https://www.brewersassociation.org/statistics/by-state/>.
Bullen, G. & Austin, R. 2014 Enterprise budget: Small-scale commerical hops production in North Carolina. North Carolina State Univ., Raleigh, NC
Burgess, A. 1964 Hops: Botany, cultivation, and utilization. Interscience, New York, NY
Darby, P. 2007 The UK hop breeding programme: A new site and new objectives, Tettnang, Germany. (Intl. Hop Growers’ Convention)
Davis, J. 2014 Growing hops in the southeast, Afton, VA. (Virginia Hops Wkshp.)
Davis, J. & King, S. 2012 Hop production in North Carolina. North Carolina State Univ., Mills River, NC
Dean, A. & Voss, D. 1999 Design and analysis of experiments. Springer, New York, NY
Florida Automated Weather Network 2011 Florida Automated Weather Network. 18 Jan. 2015. <http://fawn.ifas.ufl.edu/>.
George, A. 2014 2014 Hop growers of America statistical report. Moxee, WA
Goiris, K., Jaskula-Goiris, B., Syryn, E., Van Opstaele, F., De Rouck, G., Aerts, G. & De Cooman, L. 2014 The flavoring potential of hop polyphenols in beer J. Amer. Soc. Brew. Chem. 72 135 142
Hieronymus, S. 2012 For the love of hops: The practical guide to aroma, bitterness and the culture of hops. Brewers Publications, Boulder, CO
Hofte, A.J.P., van der Hoeven, R.A.M., Fung, S.Y., Verpoorte, R., Tjaden, U.R. & vad der Greef, J. 1998 Characterization of hop acids by liquid chromatography with negative electrospray ionization mass spectrometry J. Amer. Soc. Brew. Chem. 56 118 122
Hop Growers of America 2009 Hop variety manual. Moxee, WA
Howard, G.A., Slater, C.A. & Tatchell, A.R. 1957 Chemistry of hop constituents XI. Some observations on the isomerization of humulone J. Inst. Brew. 63 237 248
Lombard, K., McCarver, K., Thomas, F.J., Acharya, R. & Bates, T. 2014 What’s hop’pening in northwest New Mexico? Hops (Humulus lupulus) trials summary 2009 to 2014, Orlando, FL. (Amer. Soc. Hort. Sci.)
Moritz, E. & Morris, G. 1891 A text-book of the science of brewing. E. & F.N. Spon, London, UK
National Resources Conservation Service 2011 National Resources Conservation Service. 18 Jan. 2015. <http://websoilsurvey.nrcs.usda.gov/app/HomePage.htm>.
R.N.V. Enterprises. 2014 Hop variety descriptions. Yakima, WA
Seigner, E., Lutz, A., Oberhollenzer, K., Seidenberger, R., Seefelder, S. & Felsenstein, F. 2008 Breeding of hop varieties for the future, Ghent, Belgium (Second Intl. Humulus Symp.)
Tremblay, C.H. & Tremblay, V.J. 2011 Recent economic developments in the import and craft segment of the US brewing industry. Oxford Univ. Press, Oxford, UK
USDA 2015 Crop Values 2014 Summary. Washington, DC
Van Opstaele, F., Causmaecker, B.D., Aers, G. & Cooman, L.D. 2012 Characterization of novel varietal floral hop aromas by headspace solid phase microextraction and gas chromatography-mass spectrometry/olfactometry J. Agr. Food Chem. 60 12270 12281
Welch, D. 2007 Hops shortage likely to boost price of beer, Morning Edition, Natl. Public Radio, Washington, DC