Chamaecrista nictitans

Small-Flowered Partridge-Pea, Sensitive Pea

Chamaecrista nictitans plant2

Family - Fabaceae

Habit - Taprooted annual forb, with nodules present on roots.

Stems - Ascending to erect, to 40 cm, widely branching above the base, herbaceous but stout at the base, antrorse pubescent.

Chamaecrista nictitans stemStem.

Leaves - Alternate, stipulate, even-pinnate, with 6-18 pairs of leaflets. Stipules erect, appressed, narrowly lanceolate-triangular, usually somewhat asymmetric, acuminate, conspicuously nerved, 3-6 mm long, 1.2-1.4 mm wide at the base, green but often with a reddish apex, glabrous or inconspicuously hairy. Gland of the petiole 0.5-1.0 mm long, usually stalked, purplish. Petiole and rachis antrorsely pubescent. Leaflets sessile, opposite, entire, 6-10 mm long, 1-2 mm broad, oblong, oblique at the base, mucronate, glabrous or minutely hairy, deep green adaxially, light green abaxially, lateral veins evident abaxially.

Cassia mictitans stipuleStipule and gland.

Chamaecrista nictitans leaf1Leaf.

Inflorescence - Axillary, of solitary or paired flowers, the stalks 2-3 mm long, the bracts linear-lanceolate, 1.5-2.0 mm long, exceeding the pedicel. Pedicels short, to 1.2 mm long.

Chamaecrista nictitans inflorescenceInflorescence.

Flowers - Strongly asymmetric, 8-10 mm in diameter. Sepals 3-4 mm long, lanceolate, sharply pointed, hairy. Petals dimorphic, glabrous, with 1 larger petal 4-6 mm long, 3-4 mm wide, obovate, tapered to a stalklike base; and 4 smaller petals 2.6-3.0 mm long, 1.5-2.0 mm wide, yellow. Stamens 5 (rarely with 1 or 2 additional smaller staminodes), slightly unequal, oriented toward the lower side of the flower, glabrous, the filaments whitish, short (to 1.2 mm long), the anthers 1.4-2.0 mm long, purplish or reddish, apically dehiscent. Ovary 1.5-2.0 mm long, green, hairy, the style 1.4-1.6 mm long, greenish, glabrous.

Cassia mictitans flowerFlower.

Chamaecrista nictitans flower2

Cassia mictitans calyxCalyx.

Fruits - Legumes 2.0-3.5 cm long, 4-5 mm wide, finely hairy. Seeds 3.0-3.2 mm long, 1.5-2.0 mm wide, nearly square, the surfaces finely pitted, dark brown, shiny.

Cassia mictitans fruitsFruits.

Flowering - July - September.

Habitat - Glades, forest openings, bluff ledges, fields, pastures, roadsides, railroads. Usually on acid soils.

Origin - Native to U.S.

Lookalikes - Chamaecrista fasciculata.

Other info. - This little species can be found in Missouri mainly south of the Missouri River. Its U.S. range encompasses the southeastern and New England portions of the country. When in flower, the plant is easy to ID because of its small yellow flowers and finely pinnate leaves. In the absence of flowers it is difficult to distinguish from its showier sibling, C. fasciculata.

The leaves are sensitive to the touch and will close when touched or struck by strong sunlight. This action, however, is not nearly as quick or dramatic as it is in other species from the family. Traditionally the roots of this species were used to make a tea that was believed to relieve fatigue. The fruits can be glabrous or hairy and are eaten by wildlife.

Photographs taken in Brown Summit, NC., 9-8-02 (DETenaglia); also at Holly Ridge Conservation Area, Stoddard County, MO, 8-15-2009, and Sand Prairie Conservation Area, Scott County, MO, 8-12-2015 (SRTurner).


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