As for why it became known as ong choy, there are several theories: one suggests that when traders brought it from overseas, they "transported it in earthen jars on ships"—since ong shares the same pronunciation as the word for jar, it became known as "jar vegetable." Another theory is that you only need to cover the stem joints with soil for it to root and flourish—since the character shares the same pronunciation as the word for "heaping soil" in Taiwanese and Hakka dialects, it earned this name from its easy cultivation method.

Water spinach thrives in warm climates and grows year-round in Taiwan, with cultivation possible everywhere except northern Taiwan during winter months. The main growing regions include Changhua, Yunlin, Chiayi, and Pingtung counties. When fresh, the leaves are crisp, tender, and juicy with no bitter notes. Thanks to high yields and low cost, water spinach has become one of the most common blanched greens served at noodle shops and restaurants across the island.

Water Spinach on Pudu Altar Tables: A "Hollow-Hearted Gesture"

While readily available in Taiwan, water spinach becomes a precious commodity in snowy Western countries—sometimes impossible to find at any price. This transforms the humble vegetable into nostalgic food for overseas Taiwanese, who eagerly devour water spinach dishes when they return home.

During the Ghost Month Pudu rituals, no matter how lavishly the altar table is set with offerings from sacrificial meats to elaborate pastries, water spinach remains essential. In leaner economic times, water spinach's affordability made it the easiest dish to prepare for hǎo xiōngdì (literally "good brothers"—a polite Taiwanese term for wandering spirits). The vegetable's hollow stems carry deeper meaning—the "emptiness" suggests keeping emotional distance from these otherworldly guests, conveying "sincere hospitality without inviting them to stay." The water spinach on altar tables must be barely blanched, left half-cooked to symbolize keeping one's distance—this gentle hint encourages the spirits to continue their journey rather than linger in the mortal realm.