Until about 1900, there were no large scale, scientific attempts to cultivate new varieties of hops. There were some known varieties, but they were identified primarily by geography and gross differences in the plants' characteristics. While hops were propagated by root cuttings, "cloning" certain genomes, little effort was expended in preserving specific strains or in producing new, high quality cultivars. On top of this,
crop yield was highly variable from year to year, due to the effects of disease, pests, and rainfall. Farmers would experience a full crop yield perhaps once in a decade, leading to overplanting, which in turn caused large variances in the supply and price of hops between good and bad harvests. Wye College started a hop cultivation program in 1904 to address this issue by applying new principles of
plant breeding to the crop. By 1917, Salmon and Wye had partnered with the
East Malling Research Station to grow hops on a larger scale, in order to evaluate the commercial properties of promising crosses. Salmon's first goal for the hop breeding programme, as an extension of his research in plant pathology, was to develop disease-resistant strains. Through Salmon's career, hops were known to be a bittering agent, but research and interest in hops, particularly those originating in the Americas, was around the preservative value of the hops, the source of that value, and methods of measurement. Despite this value, brewers generally regarded American-grown hops as inferior, because of their higher levels of bitterness and particularly because of aromas considered unpleasant at the time. Salmon noted early on that English brewers were forced to blend in American-grown hops for their higher preservative value, despite this inferiority, and his breeding research expanded to include this criterion. As his research was directed toward commercial exploitation of hops, the published summaries generally included the parentage of each variety, comparative crop yield, resistance to common diseases, "resins-contents" (α- and β-acids), and particularly the results of commercial brewing trials with promising strains.
Methodology It can take a decade or more to bring a single variety from first breeding to full scale farming and some of Salmon's hops took far longer than this to see commercial use. Brewer's Gold was first planted in 1919, but not released until 1934, nearly two decades later. Cross OZ97a was first bred in 1921, did not reach farm trials until 1957, and it has only been released for commercial cultivation as of 2014. At the time Salmon began his research, the accepted method for breeding hops was to simply cross the best representatives of a given variety. Recognizing that he could only make incremental improvements to a
cultivar in that way, Salmon decided to inject new breeding material into the existing English stock. He collected hops from the United States, Canada and continental Europe and began crossing them with traditional English varieties. Because of the hit-or-miss nature of finding valuable new varieties, Salmon's procedure was to cross hundreds or thousands of plants each year. By 1930, he said he had grown more than 10,000 seedlings. Some crosses, particularly early in the program, were by open pollination. Later, to select for specific characteristics, field workers would bag each cluster of cones before the female
bines flowered, to protect them from wild pollination. They would then apply pollen from a selected male plant to the flower with a paint brush and reseal the bag. Once seeds had formed, the bags could be removed. The seeds would then be planted the following year and evaluation of the new cross could begin the year after that. To identify individual plants, Salmon assigned a sequential letter (and later, pairs of letters) to each row garden and a number to each hill in the row. If a plant was later replaced, a lower case letter was appended. For example, cross C9
a was in the third row, ninth hill, and was the second seed planted in that location. Once a likely candidate had been identified and grown to a scale useful in brewing at East Malling, Salmon and his colleagues would submit it to several brewers for trials "in copper." Following a successful brewing trial, the hops would be released to selected farmers for commercial growing trials before being released. A significant portion of his reports each year were dedicated to these commercial brewing and growing tests. ==Awards==