A look at the fruits makes it clear why this plant is called Seedbox –numerous little brown boxes no larger than ¼ inch in diameter are visible in the winter when leaves are absent. Seedbox grows 2-3 feet tall, and has many branches with smooth stems, covered with the almost-square fruits. In summer small, yellow flowers with 4 petals and 4 stamens appear next to each leaf along the stem. Each flower lasts only a single day, but there are always blooms along the many branches of each plant. Evening-primrose flowers are similar, but those of Seedbox are smaller.
This native perennial grows mostly in swamps and wet soil, and along stream edges. With many seeds in each little seedpod, the plant can be aggressive in the home garden. This native perennial occurs wild in nearly every county in Virginia, and ranges from Massachusetts and south Ontario to Iowa and southern Nebraska, south to Florida and Texas. Flowers appear in July and August, and are heavily visited by native bees, sucking nectar and collecting pollen.
The species name comes from the fact that the leaves are arranged alternately on the stem. Honored by the genus name, Christian Gottlieb Ludwig was a professor of botany at Leipzig 1709-1773.
Photo: Seedbox (Ludwigia alternifolia) taken by Helen Hamilton