Water shield, an aquatic plant, is fond of warmth and apt to grow in port areas under clean and calm water conditions. Water shields are separated into red stem and green stem varieties. They are largely planted around Tomb-sweeping Day (in early April). They may also be planted around White Dew Day (in late August).

After growing for about two months, the plants are then edible. The leaves will float on the surface of the water, looking oblong and tender. The leaves' backs contain glue-like transparent materials. The tender leaves and stems of water shields can be cooked into a delicious soup, rich with nutrition.

Zhang Han, a man of letters of Western Jin Dynasty, sighed with emotion in longing for Chun Lu, a nickname for water shields. It seemed that Zhang, a senior official in Luoyang City, missed the delicious food of his hometown so much that he was considering resigning.

Nowadays, water shields are stored in bottles or packaged into cans and are accessible throughout the year