Cassia chamaecrista L.

Cassia chamacrista plant

Family - Fabaceae

Stems - From a taproot, herbaceous, to .75m tall, erect, with antrorse pubescence, branching, often purplish.

Leaves - Alternate, stipulate, petiolate, even-pinnate, with +/-13 pairs of leaflets. Stipules attenuate, +1cm long, -2mm broad at base, with antrorse pubescence, erect, green. Petiole with a glad on the adaxial surface. Gland stalked, (the stalk to .5mm long), -1mm in diameter. Leaflets opposite, sessile, entire, glabrous, glaucous below, green above, mucronate, oblique at the base, 5mm broad, 2cm long, linear.

Cassia chamacrista glandGland at base of petiole.

Inflorescence - Short pedunculate fascicles of flowers from the internodes of the stem. Fascicles with +/-5 flowers each. Pedicels subtended by an attenuate bract. Bracts much like the stipules in form. Pedicels to +/-2cm long, antrorse pubescent, with a pair of opposite bracts in the apical 1/3. Bracts like the stipules in form.

Cassia chamacrista inflorescence

Flowers - Petals 5, yellow, glabrous, unequal, uppermost being the largest, to 2.5cm long, 2cm broad, orbicular. One of the lateral petals typically cupped over the other floral organs. All petals short-clawed and reddish at the base. Stamens 10, unequal, erect, to 1cm long. Anthers purple. Pistil deflexed. Ovary to 4mm long, with dense white matted hairs. Style to +1cm long, greenish white, becoming glabrous towards apex, curved. Sepals 5, linear to linear-lanceolate, 1.7cm long, 4mm brad, spreading, greenish with a yellowish midvein, margins scarious. Fruits compressed, glabrous to short appressed-pubescent, to +6cm long, +5mm broad, elastically dehiscent.

Cassia chamacrista calyxCalyx.

Cassia chamacrista flowerFlower close-up.

Cassia chamacrista fruitsDeveloping fruits.

Flowering - June - October.

Habitat - Prairies, glades, fields, roadsides, railroads.

Origin - Native to U.S.

Other info. - This is an extremely common plant throughout Missouri. The large yellow flowers are easy to spot along roadways. The fruits of this species are elastically dehiscent and can fling seeds quite a good distance. Hence, the plant spreads quickly and can take over a garden if not controlled carefully.
Steyermark lists different varieties and forms for the plants based on stem pubescence and flower color (which can also be white), but I won't go into those here as some may no longer be valid.
Many ID books and botanical keys mention that the way to differentiate between this species and the very similar C. nictitans L. is by the presence or absence of a stalk on the gland which is at the base of the leaf petioles. I have found this characteristic to not hold-up in the field at all. The best way to tell the two species apart is by the flower, which is very different in size between the two species. Vegetatively the two species are practically identical.
A synonym for the plant is Cassia fasciculata Michx.

Photographs taken off 63rd St, Jackson County, MO., 7-22-00, and in Ellington, MO., 6-7-03.


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