Yellow floating heart (Nymphoides peltata)

Yellow floating heart flower. © Greg Bales

Yellow floating heart is an aquatic, bottom rooted perennial plant that is native to Eurasia and the Mediterranean Sea region. It was popular as an ornamental plant for water gardens in North America, but has escaped from cultivation and become invasive in Canada and the US.

Yellow floating heart grows from a rhizome anchored in the soil. It prefers to grow in slow moving waters in lakes, rivers, ponds, and marshes. It typically grows in water between 0.5 and 4 m deep but can also survive in wet mud. Its heart shaped leaves are usually opposite and unequal, measuring 3 – 10 cm across. The leaves float at the water surface and have wavy, slightly scalloped edges and a pink or purple tinge on their undersides. Yellow floating heart produces bright yellow flowers that are held above the water by a single long stalk. Each flower has five petals arranged like the spokes of a wheel. Yellow floating heart is known for its long blooming period which lasts from July to September. The seeds produced are contained in beaked capsules. They are flat, oval, about 3 mm long, and are capable of floating with the aid of hairs on their edges. The hairs allow the seeds to attach to waterfowl and other animals, which helps in their dispersion. Yellow floating heart can also reproduce vegetatively by fragmentation.

Yellow floating heart is typically planted deliberately by water gardeners. From a water garden, it can escape to natural waterways either through flooding or attaching its seeds to waterfowl and other animals. In aquatic ecosystems, it can form dense mats of vegetation that shade or crowd out native aquatic plants. In extremely dense stands, it can cause the water to become stagnant, resulting in lower dissolved oxygen levels, which harm fish and other aquatic organisms.

The best way to stop the spread of yellow floating heart is to not plant it in the first place, especially in areas that may be flooded or in areas that are connected to natural water courses. Consider using native aquatic plants for water gardens instead. In established populations, control is very difficult. However, manual removal such as cutting and harvesting can be done to stop the plant from further spreading. Barrier material can also be used in some situations to suppress growth of yellow floating heart, however fluctuating water levels make this technique difficult.