due to the desire to maximize crop yield from relatively small plots without using excessive amounts of pesticides or fertilizers. Increased production is also driven by a desire to minimize Taiwanese dependence on other countries as sources of fresh produce, especially high value vegetables. Taiwan's vertical vegetable farms are some of the most advanced in the world. Taoyuan's iFarm was Asia's largest vertical farm when it opened in 2018. Sweet potatoes Sweet potatoes have been grown in Taiwan since at least 1603 following their introduction to Asian by the Spanish. However the possibility exists that the sweet potato reached Taiwan before the Spanish colonization of the new world. It rapidly became a staple of local diets. Poor families would often mix sweet potato into their rice or millet to stretch it out. Unlike the other staples of rice and millet, sweet potatoes could be grown on hillsides with limited preparation. Cultivation of sweet potato reached its height during the Japanese colonial period with Taiwan ranking fourth in output from 1934 to 1938 after China, Japan, and the United States with 3.7% of world production. Production fell as a result of World War II and economic disruption. It took off again in the 1950s and 1960s but with most of the crop destined to feed hogs not people. Production fell again after commercial swine producers switched to imported grains like corn for their feed. In modern Taiwan sweet potatoes are grown as a root vegetable, as a leaf vegetable, and for their starch. 40% of the crop is exported to Singapore and Hong Kong with the rest being consumed domestically either fresh or processed. Sweet potatoes are associated with poverty and their consumption is avoided by many elders however sweet potatoes continue to play an important part in Taiwanese cuisine. Research into the sweet potato at the Chiayi research station of the Taiwan Agricultural Research institute began in 1922. For the first 20 years after its founding in 1971 the World Vegetable Center was a major global sweet potato research center with over 1,600 ascensions in their first two years of operation. In 1991 the World Vegetable Center chose to end its sweet potato research due to high costs and other institutions with a tighter focus coming into existence. The WVC duplicated and transferred its research and germplasm to the International Potato Center and Taiwan Agricultural Research institute. The counties of