This species was long known as Sesbania exaltata (Raf.) Rydb. (treated here as a synonym), but the discovery of an earlier basionym led to a name change to Sesbania herbacea by R. McVaugh in Flora Novo-Galiciana 5: 695. 1987.
Further confusing the issue has been the question of whether this taxon is a distinct species or merely an annual derivative of a tropical perennial species commonly known as Sesbania emerus (Aubl.) Urb. We are following the treatment in [], which treats them as one species under Sesbanea herbacea.

Common Name: Colorado River Hemp

General Information

Sesbania herbacea is an erect, large, succulent-stemmed, open-branched plant with few, wide-spreading branches, it can grow 70 - 400cm tall. An annual in regions with frosts, it is a herbaceous perennial to sub-shrub in the tropics[, , ].
The plant is harvested from the wild for local use as a source of fibre. Ir is often grown as a soil stabilizing and improving crop in plantations etc.
Sesbania herbacea may easily become an invasive weed. It is a serious weed in soybean, cotton, sweet potatoes, and rice[]. Because it tends to colonize the banks of waterways and distribute its seed by water, it may be easily spread over a large area via watercourses. It can be an opportunistic plant in disturbed, less flooded, higher elevation sites[].

Known Hazards

The seeds may be poisonous[]. The seeds contain saponins and other toxic compounds that cause severe diarrhoea and internal hemorrhaging[].
Although poisonous, saponins also have a range of medicinal applications and many saponin-rich plants are used in herbalism (particularly as emetics, expectorants and febrifuges) or as sources of raw materials for the pharmaceutical industry. Saponins are also found in a number of common foods, such as many beans.
Saponins have a quite bitter flavour and are in general poorly absorbed by the human body, so most pass through without harm. They can be removed by carefully leaching in running water. Thorough cooking, and perhaps changing the cooking water once, will also normally remove most of them. However, it is not advisable to eat large quantities of raw foods that contain saponins.
Saponins are much more toxic to many cold-blooded creatures, such as fish, and hunting tribes have traditionally put large quantities of them in streams, lakes etc in order to stupefy or kill the fish and make them easy to catch[].

Botanical References

, ,

Range

Widespread, often as a result of cultivation, from Argentina, north through the Americas to southern USA. Probably genually native in Mesoamerica

Habitat

Fields and low ground[]. Bottomland forests, banks of streams, and margins of oxbows and sloughs; also edges of crop fields, railroads, roadsides, and open disturbed areas[]

Properties

Weed Potential	Yes
Other Uses Rating
Habit	Annual/Perennial
Height	2.50 m
Growth Rate	Fast
Pollinators	Bees
Self-fertile	Yes
Cultivation Status	Cultivated, Wild

Cultivation Details

Sesbania herbacea is not very cold tolerant, being killed by light frosts. In frost-free regions the plant perennates with a main stem that often becomes woody with age[]. It grows best in regions with hot summers and low humidity[].
Grows best in a sunny position. Grows well in alluvial clay soils[]. Requires a moist soil for best growth and can tolerate some flooding once it reaches seedling stage[]. Established plants are drought tolerant[]. Succeeds in soils with a pH in the range 4.5 - 7.2[].
A fast-growing species, it can commence flowering just 45 - 50 days after sowing and continue to produce seed for a long period[].
This species has a symbiotic relationship with certain soil bacteria, these bacteria form nodules on the roots and fix atmospheric nitrogen. Some of this nitrogen is utilized by the growing plant but some can also be used by other plants growing nearby[].

Edible Uses

None known

Medicinal

None known

Agroforestry Uses:

The plant is grown mainly for use as a soil-stabilizing and soil-improving crop. It can produce 2 to 3 ton/acre in 75 days in above ground biomass. It was once used extensively as a cover crop in citrus groves, as well as by cotton and truck crop growers in California[, ].
When used in rotations it is recommended to dig the plant into the soil early, after 6 - 9 weeks of growth and before seed-set in order to avoid weediness. The plant can tolerate high mowing, and should be mown before incorporation into the soil[].
In Sinaloa Mexico, the plant was found to have higher yield, require less weed cultivation, and was less susceptible to pests than cowpea (Vigna unguiculata). The plant tends to sprawl and can be supported with sorghum sudangrass when grown in a warm-season mixture. Growing bigpod sesbania onto a support such as sorghum sudangrass will help the plant increase height, thereby optimizing plant leaf position and improving photosynthesis[].
Glands on the leaf margins secrete sugars that attract beneficial predatory insects such as parasitic wasps[].

Other Uses

A strong fibre obtained from the bark can be used for making nets etc[, , ]. It was an important fibre plant for the native North American Indians[].
The stems can be pulped and used in paper production[].

Propagation

Seed - it has a hard seedcoat and benefits from scarification before sowing in order to speed up and improve germination. This can usually be done by pouring a small amount of nearly boiling water on the seeds (being careful not to cook them!) and then soaking them for 12 - 24 hours in warm water. By this time they should have imbibed moisture and swollen - if they have not, then carefully make a nick in the seedcoat (being careful not to damage the embryo) and soak for a further 12 hours before sowing.