Ludwigia alternifolia aka Rattlebox

Ludwigia alternifolia is a wildflower from eastern North America. It is a perennial, so it lives for years. People call it seedbox, rattlebox, and alternate-leaved seedbox. It belongs to Onagraceae, the evening primrose family. Its range runs from southern Quebec and Ontario to Kansas. It reaches south to Texas and Florida. Wild plants grow in marshes, wet meadows, and swamps. They also grow by streams, ponds, and wet ditches. In Missouri, they grow in low woods and wet prairie hollows.

The plant grows upright, with many branches and smooth stems. Garden plants reach about 1.5–3 feet [0.46–0.91 metres] tall. Some reach 4 feet [1.22 metres]. They spread about 1–1.5 feet [0.30–0.46 metres]. The green stems often take on a red tint. Dark green leaves grow along them in an alternate pattern. This means they grow in turn, not in pairs. Each simple leaf has one blade, with a smooth edge. It has a sharp tip and a short stalk. The narrow leaves have the shape of a lance. They can reach 0.33 feet [0.10 metres] long. The plant sheds its leaves; it does not stay evergreen.

Small yellow flowers grow on short stalks at leaf joints. Each has four petals and the shape of a cup. A bloom lasts one day or less, then drops its petals. Four green sepals stay after the petals fall. Missouri Botanical Garden lists blooms from June through August. North Carolina State lists a longer season: May through October. Bees do most of the work of pollination. Small, square seed pods, called capsules, follow the flowers. Each holds many seeds. Shaking the pods makes them rattle, which explains the common names. Fruits can stay on the plant from June through November.

Grow seedbox in full sun, in soil that stays damp. It can also take some light shade. It prefers acidic, sandy soil but accepts other soil types. Its listed growing conditions also include clay and loam. It can take heat and wet ground. Sources place it in USDA hardiness zones 4–8. Missouri Botanical Garden says it is easy to grow. It may sow its own seeds where conditions suit it.

Seedbox suits native gardens, rain gardens, and pond edges. It also fits water gardens and moist areas left natural. Both its yellow flowers and seed pods add garden interest. Bees visit the blooms. Pearly wood nymph caterpillars eat the plant. Missouri Botanical Garden reports no major problems with insects or disease. The supplied sources do not establish whether people can eat it. They also do not establish whether it is toxic.