This rare plant has attractive foliage, but blooms sparingly. In the photograph of the flowering plant on the lower right, one of the sickle-shaped seedpods is evident; it is still green. Sicklepod resembles Senna marilandica (Maryland Senna) and Senna hebecarpa (Wild Senna) somewhat in appearance, but it is a shorter annual plant that has 1) fewer leaflets per compound leaf, 2) leaflets with a more obovate shape, and 3) seedpods that are more curved and slender. In the past, Sicklepod was often assigned to the Bean family (Fabaceae), rather than the Caesalpinia family. Return
The preference is full sun and moist to slightly dry conditions. This plant tolerates different kinds of soil, from fertile loam to gravelly soil; in fact, it often thrives in railroad ballast. Drought tolerance is good, and the foliage is rarely bothered by foliar disease. It is somewhat slow to develop for an annual plant, and tends to bloom late in the year in Illinois. Range & Habitat
This annual native plant is 1-2½' tall, branching occasionally. The stems are light green and somewhat ridged. The lower stems often sprawl along the ground in open areas, otherwise this plant is erect. The compound leaves alternate along the stems. They are evenly pinnate, usually with 3 pairs of leaflets, and have long leaf stems (primary petioles). The obovate leaflets are individually 1½" long and 1" across. They are devoid of hairs and pale green on their undersides. There is an extra-floral nectary close to the lowest pair of leaflets on the upper side of each compound leaf. This nectary resembles a small brown spike. The foliage has a slightly rank odor. One or two flowers develop from the upper axils of the compound leaves. These flowers have pedicels about 1" long and tend to nod slightly downward. They are about 1" across, and consist of 5 rounded yellow petals and 10 stamens; the petals are often slightly unequal in size. The flowers are subtended by a light green calyx that is divided into 5 folded sepals; these sepals are shorter than the petals and hairless. In Illinois, the blooming period occurs from late summer through the fall, and lasts about 1-2 months. There is no floral scent. A long seedpod develops from each flower that is 4-6" long, but only 1/3" across. This seedpod curves downward and resembles a sickle in its overall shape. The root system consists of taproot. This plant spreads by reseeding itself.
The green leaves of the plant are fermented to produce a high-protein food product called "kawal" which is eaten by many people in Sudan as a meat substitute. Its leaves, seeds, and root are also used in folk medicine, primarily in Asia. It is believed to possess a laxative effect, as well as to be beneficial for the eyes. As a folk remedy, the seeds are often roasted, then boiled in water to produce a tea. The plant's seeds are a commercial source of cassia gum, a food additive usually used as a thickener and named for the Chinese Senna's former placement in the genus Cassia. Roasted and ground, the seeds have also been used as a substitute for coffee. In traditional Korean medicine, they are called gyeolmyeongja (결명자) and usually prepared as tea. They are also used in Kampō (traditional Japanese medicine), where they are called ketsumei-shi (ケツメイシ, 決明子) or by their Chinese name jué míng zǐ (traditional: 決明子, simplified: 决明子).
Apart from "sicklepod" and "Chinese senna", S. obtusifolia has a wide range of common names. It is also known in English as Foetid Sassia (or "cassia"), Sickle Senna, Coffeeweed or Arsenic Weed, and somewhat ambiguously as "blunt-leaved senna", "coffee pod" or "java bean". The scientific name means "blunt-leaved senna", with obtusifolia coming from Latinobtusus ("dull", "blunt") + folium ("leaf").
Chinese Senna has been treated under a wide range of scientific names. Some are synonyms of Senna obtusifolia, others are names that have been applied to it in error. In addition, several of these names may also refer to related plants. In particular, the distinction between this species and Senna tora was fraught with errors and misunderstandings:
Kawal, a protein-rich meat substitute eaten in Sudan, is produced by crushing the leaves of the plant into a paste which is then traditionally fermented in an earthenware jar, buried in a cool place. The jar is dug up every three days and the contents mixed. After two weeks, the paste is removed and rolled into balls which are left to dry in the sun. They are usually cooked in stews with onions and okra.
This plant is a conspicuous member of the flora of its native home. It evoked powerful images to the celebrated Tang Dynasty poet Du Fu (杜甫), who in one of his "Sighs of Autumn Rain" poems (Qiū yǔ tàn, 秋雨叹) discussed it thus:
In autumn rain, the grasses rot and die, / Below the steps, the Chinese Senna's colour is fresh. Full green leaves cover the stems like feathers, / And countless flowers bloom like golden coins. The cold wind, moaning, blows against you fiercely, / I fear that soon you'll find it hard to stand.
Upstairs the scholar lets down his white hair, / He faces the wind, breathes the fragrance, and weeps.