Showy Partridge Pea

Chamaecrista fasciculata (formerly Cassia fasciculata)

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Photo of showy partridge pea showing flowers, buds, and leaves.
The interesting, bright yellow flowers of showy partridge pea are immediately recognizable.
Family

Fabaceae (beans, peas)

Description

Showy partridge pea is an annual with upright stems, usually without branches. Flowers 1 to several, about 1 inch across, arising from leaf axils. Petals 5, yellow (rarely white), sometimes reddish-tinged at the base; one side petal curves around the stamens; the lowest petal is the largest. Blooms July–October. Leaves compound, pinnately divided, with up to 18 leaflets that are narrow, short, linear. Leaflets fold up along the midrib at night into a sleeping position, and often upon being touched. Fruit a legume (short beanlike pod) 1–2½ inches long, black when mature. When mature and dry, the two sides separate suddenly, flinging the seeds a yard or more away.

Similar species: Small-flowered, or sensitive partridge pea (C. nictitans) is about half as tall, branches a bit more, and has inconspicuous flowers no bigger than about ½ inch wide. It grows mostly south of the Missouri River.

Size

Height: commonly to 2 feet, sometimes nearly 3 feet.

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Photo of showy partridge pea plant in a field.
Showy Partridge Pea
The leaflets of showy partridge pea fold up along the midrib at night into a so-called sleeping position.

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Photo of showy partridge pea plant showing flowers, leaves, and young fruits.
Showy Partridge Pea
Showy partridge pea is one of the most commonly seen roadside plants of early fall.

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Showy partridge pea pod
Showy Partridge Pea Pod
The fruits of showy partridge pea are legumes that are 1–2½ inches long and turn black when they mature. These are literally bean pods, because they are in the bean family. When mature and dry, the two sides of the pod separate suddenly, flinging the seeds away.

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Partridge pea branch tips with partially closed flowers
Showy Partridge Pea
In partridge peas, the special arrangement of the flower parts encourages what is called “buzz pollination” by bumblebees.
Habitat and conservation

Occurs in fields, pastures, waste places, roadsides, and railroads, as well as glades, upland prairies, openings in upland forests, savannas, ledges and tops of bluffs, and banks of streams and rivers. Partridge pea is one of the most commonly seen roadside plants of early fall. Nyctinasty, the plant’s tendency to close up its leaflets at night, is thought to be an adaption to control water loss or afford protection from herbivores. Many members of the bean family exhibit this characteristic.

image of Showy Partridge Pea distribution map
Distribution in Missouri

Scattered to common nearly statewide.

Human connections

This plant has incredibly interesting flowers, and people enjoy figuring out how they work. The special arrangement of flower parts, for example, encourages what is called “buzz pollination” by bumblebees, and ants visiting nectar glands in the leaf stems remove the plant’s insect pests.

Ecosystem connections

Our two partridge pea species are important wildlife food plants and are sometimes planted for this purpose. Deer and livestock eat the nutritious foliage, though some compounds in the plant can cause digestive upset if too much is eaten. Quail, turkey, and other birds are fond of the seeds.