Corn cultivation

The research of H. O. Werner as the university horticulturalist before him served as the template for Yeager's work, and he aimed to create a cultivar of sweet corn that was better than even the Golden Bantam, the most popular variety at the time. Making attempts at hybridization with Gill's Early Market variety, he finally succeeded in creating a worthwhile enough cross in 1923, though had to go through another round of replantings to have enough seed in 1924 to send out to farmers for testing in the 1925 season. It took another year until 1926 when he had worked out some additional negative traits from the cultivar, allowing him to then officially announce the new Sunshine variety of sweet corn. The farmer testing that year proved successful, and the cultivar was listed in the seed catalog for 1927 published by Oscar H. Will & Company.^[4]

Tomato cultivation

At the same time as his corn research, Yeager was doing research into tomatoes and how to extend Werner's work in creating a tomato, which is normally a warm-weather fruit that requires large amounts of sunlight, that could grow successfully in North Dakota without requiring the involvement of a specialist. Yeager, however, was less positive about the potential of improvement, as even the popular national variety with cold resistance at the time, the Earliana, did not reach fruiting early enough for the especially early frosts that occur in the state. An attempt on his part in the 1920s resulted in a hybrid cross of the Earliana with the Sunrise tomato from England; the new resultant variety was named Red River and opened for cultivation in 1925. It was not good enough for what Yeager was desiring, however, and multiple further cultivars would be released, including the Agassiz and the Early Jumbo.^[4]

It was not until 1929 and his production of the Bison tomato that Yeager decided he had made a satisfactory early-growing tomato. It was officially released that same year. In a comparative study he conducted in 1931 against 26 other cultivars, the Bison tomato produced 50 percent more fruit than the other cultivars by the endpoint. By 1933, the Bison tomato had become the most planted tomato cultivar in the region. Due to the tomato being one of the few determinate cultivars produced at the time that grew fruit on the end of each vine, there was criticism of the cultivar by other scientists that claimed the hardier variety would not be necessary or wanted outside of the colder states. This would be upended throughout the 1930s though as determinate tomatoes became a highly desired cultivar in states like California. An additional tomato cultivar of Yeager's, the Farthest North, would become the dominant tomato in Costa Rica over the next two decades.^[4]

Another tomato improvement that Yeager aimed for was a nutritionally improved cultivar due to the high amount of vitamin A and vitamin C in tomatoes. He was able to create the Doublerich cultivar with double the vitamin C than other tomatoes during his time at the university, but it was not released for farmers until 1947, after he had left his position there.^[4] He also worked on cultivars that are more ornamental in nature, with the Window Box cultivar being released in 1945 that featured a small 18 inches (460 mm) in height, a single fruiting stem, and bunches of tomatoes that were each between 1 and 2 inches (25 and 51 mm) in diameter.^[7]

Winter squash cultivation

Another crop that Yeager began investigating was sweet potatoes thanks to their high nutrient levels, but determined that the growing season of North Dakota was too short for any hybrid cultivar or other trait improvement to overcome. So he turned to winter squash instead in 1922 and worked until 1925 with the cultivar Quality. He failed, however, to find more than a single desirable trait and found out that even that single one was due to an accidental hybridization with the Essex Hybrid cultivar. This difference interested him though, and he abandoned his other squash research to focus on this new hybrid, creating a new cultivar in 1927 called the Buttercup squash. He was convinced of its improvement over the general Hubbard cultivar after his final testing in 1931, and he eventually released the Buttercup for general farming in 1932.^[4][8]

Melon cultivation

Yeager's early work at the University of New Hampshire starting from 1936 focused on producing minuscule "midget" watermelons for easier public consumption. The first success was the creation of the White Mountain cultivar in 1943, but it had the unfortunate additional trait of producing white seeds. This made it unsellable due to that feature generally implying unripeness in other watermelons, which would put off customers from purchasing it. He ultimately triumphed in 1950 in making the New Hampshire Midget cultivar, which was a hybrid cross of the Dakota Sweet from Russia and the Favorite Honey from Japan. It was described as being sweet and having a small rind that made disposal easy.^[9] The New Hampshire Midget went on to be entered into the All-America Selections and won the 1951 gold medal for approval as a garden crop.^[10]

Next for his research, Yeager collaborated in 1951 with fellow pomologist Elwyn Meader to create a new watermelon cultivar named the Golden Midget, which was a hybrid made by crossing the New Hampshire Midget with an Oklahoma variety named the Pumpkin Rind. It took over a year and multiple generational trials to make the recessive golden rind consistent and to have other traits that allowed the melon to grow within 70 days.^[11] The Golden Midget was first released for public consumption in 1952, and by April 1953 more than 2,000 acres (8.1 km²) in Florida and over 1,000 acres (4.0 km²) in Cuba were devoted to growing the cultivar. It was especially popular for its small size, which led to it being referred to as a "refrigerator" or "ice box" watermelon.^[12][13]

Bulletin publications

The agricultural experiment stations and their researchers were tasked with releasing periodic bulletins on farming and horticultural practices and methodologies, either generally or for specific crops. This was also true for Yeager and the station at North Dakota State University. Some of the first bulletins he published include Control of Garden and Household Insects in 1921 and Shelterbelts for North Dakota that same year. These general topic bulletins would lead to ones on the plants he had been breeding, with one on his Sunshine Sweet Corn and also his Buttercup Squash. A broader, but focused bulletin titled Fruit Culture in North Dakota was published in 1925 and covered all the necessities for obtaining and planting various fruit trees and bushes in the state and how to arrange a fruit garden. Another bulletin called Tomato Breeding was released in 1933 and discussed similar methods.^[4]