False Loosestrife

Ludwigia alternifolia

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Photo of a false loosestrife flower closeup
False loosestrife has its flower parts in fours: four yellow petals, four sepals, for stamens.
Other Common Name
Bushy Seedbox; Rattlebox
Family

Onagraceae (evening primroses)

Description

False loosestrife is an erect, branching perennial. Flowers have parts in fours (4 sepals, 4 stamens, etc.) and are usually borne singly, on very short peduncles from leaf axils. Base of flower swollen (a hypanthium); 4 bright yellow petals that often are shed the same day the flowers open. Blooms June–August. Leaves lanceolate, to 4 inches long, alternate, pointed, tapering at the base to hardly noticeable stems. Fruit a 4-sided capsule, ¼ inch long, that remains on the plant through the winter (hence the name “bushy seedbox”).

Similar species: There are 11 species of Ludwigia in Missouri. This one is distinguished by its nearly spherical or cubical fruits that open at a pore at the tip, by having definite flower stalks to about ¼ inch long (the flowers aren’t sessile), and by having as many stamens as sepals.

Size

Height: to about 2½ feet; stem length approx. 2–4 feet.

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Photo of a false loosestrife plant showing flowers, buds, and leaves.
False Loosestrife (Bushy Seedbox)
The flowers of false loosestrife are on very short stalks arising from the leaf axils and have their parts in fours.

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Photo of a false loosestrife spend flower, viewed from top
False Loosestrife Young Fruit, Top View
A false loosestrife flower looks like this after the petals fall off. What will become the 4-sided "seedbox" is visible at the center.

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Photo of a false loosestrife blooming stalk
False Loosestrife
False loosestrife is a member of the evening primrose family. Note the small stems on each flower, and the interesting four-sided flower buds.

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Photo of a false loosestrife plant growing at the edge of a pond.
False Loosestrife (Bushy Seedbox)
False loosestrife grows in wet places near ponds, lakes, streams, and rivers, and in swamps, sloughs, and ditches.

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Photo of a false loosestrife plant
False Loosestrife Plant
The leaves of false loosestrife are lanceolate, alternate, pointed, and taper at the base to the small leaf stems.

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Photo of young false loosestrife fruits, shown from side
False Loosestrife Young Fruit, Side View
These spent flowers of false loosestrife show the swollen base (hypanthium) that will eventually become the "seedbox" fruit.

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Photo of a false loosestrife mature fruit
False Loosestrife Mature Fruit
By late October, the fruits of false loosestrife have matured and look like this. The many tiny seeds will fall out of the pore in the center.

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Photo of a false loosestrife crushed capsule showing the seeds it contained
False Loosestrife Seeds
If you crush a mature, dry capsule of a false loosestrife, you'll discover many, many tiny seeds.

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Photo of false loosestrife plant showing branches, leaves, and flowers.
False Loosestrife (Bushy Seedbox)
One of eleven water primrose species in Missouri, false loosestrife is distinguished by its cubical fruits that open at a pore in the tip.
Habitat and conservation

Occurs on banks of streams, rivers, and spring branches, margins of ponds, lakes, and sinkhole ponds, marshes, fens, seeps, bottomland prairies, and swamps; also ditches, railroads, and roadsides.

image of False Loosestrife Bushy Seedbox Rattlebox distribution map
Distribution in Missouri

Scattered nearly statewide, but apparently absent from most of the northwestern quarter.

Human connections

False loosestrife does well cultivated as a water plant or in a rain garden, with its bright yellow flowers and showy fruits that enable it to self-seed.

Ecosystem connections

Wetland plants can survive being flooded with water. Many animals eat wetland plants fresh, while others eat them as they decompose. Wetland plants help stabilize soils and absorb floodwater. This species apparently does not require cross-pollination in order to set seed.