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Ludwigia is a plant genus that is part of the Onagraceae family. It contains about 82 species of annual and perennial herbs that grow in aquatic environments. These plants feature yellow flowers and lance-shaped leaves that are attached to tall, branching stems. Landscapers use these plants in flower beds or containers. Regular pruning is required to prevent these plants from becoming invasive.
This genus is named after the 18th century German botanist Christian Gottlieb Ludwig. The common name for these plants is water-primrose. Many of the species have variations of the common name. For example, Ludwigia octovalvis is commonly called the Mexican primrose-willow, while Ludwigia peploides is known as the creeping water-primrose.
These plants grow along riverbanks and in swamps, or float on waterways and shorelines. They are considered invasive, since they spread quickly and consume resources needed by other plants. In some areas, they can create problems with canals and drainage ditches. Consequently, many places have designated certain species of water-primrose as noxious weeds, such as Ludwigia hexapetala and Ludwigia peploides.
Most of the species are native to North and South America. L. inclinata is distributed throughout Central and South America, while L. sedioides is concentrated in Brazil and Venezuela. L. anastomosans is endemic to Brazil.
A commonly grown plant in the United States is L. alternifolia, which is commonly called seedbox. It grows about 3 feet (1 m) in height and features bright yellow flowers that consist of four rounded petals. The flowers are about .5 inches (1.2 cm) in diameter, and they generally bloom from June to August. The common name of this plant is derived from the unique box-shaped fruits that develop after the flowers have fallen.
When growing plants from the genus Ludwigia, it is recommended to plant them in damp soil. The area should be exposed to direct sunlight, but these plants can thrive in partial shade. Most of the species grow rapidly, and they tend to reseed frequently.
In areas where the water-primrose has grown out of control, several methods are used to reduce the population. Manuals removal techniques such as cutting and raking usually clean an area thoroughly. To prevent the regrowth of the water-primrose, regular spraying of aquatic herbicides is recommended.
A benefit of having a water-primrose in a garden is that it attracts several types of butterflies. It is usually planted with similar plants such as swamp milkweed, scarlet rose-mallow, and powdery thalia.