Watershield (Brasenia schreberi) is an aquatic plant recognized by its distinctive floating leaves. This perennial herb thrives as a rooted plant with its foliage resting on the water’s surface, found in diverse freshwater environments globally.
Key Identifying Features
Watershield is characterized by a thick, clear, gelatinous mucilage covering the undersides of its leaves, stems, and developing buds. This layer, up to 0.25 inches thick, protects from herbivores and desiccation during droughts. The leaves are small, oval, or shield-shaped, 1 to 4.5 inches long, with a green upper surface and a reddish or purplish underside.
The leaf stem attaches to the center of the blade, a characteristic known as peltate, which sets it apart from other floating-leaved plants. Small, dull purple flowers emerge from the water surface, blooming from June through August, and are about 0.5 to 1 inch in diameter. Unlike water lilies, watershield leaves are smaller and lack the characteristic V-shaped notch; its flowers are also smaller and less showy.
Natural Habitat and Range
Watershield prospers in still or slow-moving freshwater bodies like ponds, lakes, and sluggish streams, rooting in bottom sediments. It prefers clear, acidic water but tolerates pH levels from 4.7 to 9.5. The plant establishes itself in water depths from shallow to 10 feet.
It is native to North America, South America, the West Indies, Eastern Asia, Australia, the Indian Subcontinent, and parts of Africa. This extensive distribution means it is present on every continent except Antarctica and Europe. Watershield can form dense stands in suitable aquatic environments across its global range.
Culinary Uses and Ecological Impact
The young stems and leaves of watershield are consumed in some Asian cuisines. In Japan, it is known as “junsai” and is considered a delicacy, often served in salads or soups. China also utilizes the plant, calling it “chúncài,” frequently featured in dishes like West Lake Water Shield Soup.
While providing a food source for waterfowl and shelter for various aquatic organisms like fish and invertebrates, watershield can also present challenges. Its growth can lead to dense surface mats. These mats block sunlight penetration, outcompete other native aquatic vegetation, reduce oxygen levels, and interfere with recreational activities like fishing, swimming, and boating.