Raising broccoli for commercial purposes began in earnest in the 1920's in California. Compared to the broccoli that we eat now, broccoli at the time was small, irregular in shape and had irregular harvest times. It was a vegetable which took a lot of effort, requiring farmers to go into the fields for harvesting any number of times.
In these circumstances, Sakata was the first Japanese company to market an F1 hybrid, called "Green Duke". With its large head, high-yield, consistent size and regular harvest times, it was easier to harvest, and yieldability improved substantially. This spurred the popularization of broccoli in the United States.