Hemp sesbania

Images above: Upper left: Hemp sesbania seedling (Jack Clark, University of California). Upper right: Hemp sesbania plant (John Gwaltney, SoutheasternFlora.com). Bottom left: Hemp sesbania flower (John Gwaltney, SoutheasternFlora.com). Bottom right: Hemp sesbania fruit (John Gwaltney, SoutheasternFlora.com).

Identification

Other common names:  coffeeweed

Family:  legume family, Fabaceae

Habit:  A tall, erect species, hemp sesbania behaves as an annual herb in most of the U.S.A. because it is killed by frost, but in perennially warm climates it is a semiwoody perennial (UC SAREP).

Description:  Cotyledons are fleshy, oblong to lance-shaped, hairless, and 0.4-1” (1-2.5 cm) long by 0.12-0.15” (0.3-0.4 cm) wide.  The first true leaf of the seedling is simple, lance shaped and 0.8” (2 cm) long by 0.2” (0.5 cm) wide.  All subsequent leaves are divided, with 4-8 pairs of short-stalked, oppositely arranged, oblong to lance-shaped leaflets with pointed tips.  Young leaves are 0.8-2” (2-5 cm) long, while individual leaflets are 0.2-0.6” (0.5-1.5 cm) long by 0.06-0.12” (0.15-0.3 cm) wide.  Leaf arrangement is alternate. Mature plants are typically 3-6 ft (0.9-1.8 m) tall but occasionally reach over 10 ft (3 m), with smooth, green, and generally unbranched stems that become woody with age.  The leaves are fern-like, alternate, 4-12” (10-30 cm) long, and divided into 20 to 70 oppositely arranged leaflets.  Each leaflet is 0.75-2.5” (2-7 cm) long by 0.1-0.3” (0.25-0.8 cm) wide, hairless above and hairless to sparsely hairy below.  Leaflet shape is similar to that of the seedling.  The taproot is large and branched.  The pea-like flowers occur in clusters of 2 to 6 on 0.7-3.8” (1.8-9.7 cm) long stalks growing from the leaf axils.  Flowers are yellow to yellow-orange, often spotted with purple, and 0.4-0.6” (1-1.5 cm) long.  Each flower is replaced by a 4-sided, curved and jointed seedpod.  The seedpods are 6-8” (15-20 cm) long by 0.1-0.2” (0.25-0.5 cm) wide with a 0.2-0.4” (0.5-1 cm) long beak at the tip.  Pods contain 30 to 40 seeds.  Seeds are oblong, 0.1-0.3” (0.25-0.8 cm) long by 0.08-0.1” (0.2-0.25 cm) wide, glossy, and solid brown to mottled tan and brown.

Similar species: Partridgepea [Chamaecrista fasciculata (Michx.) Greene] has similar foliage to hemp sesbania.  Partridgepea leaves, however, have a distinctive orange gland at the base and have fewer leaflets (16 to 30) than those of hemp sesbania.  

Management

Hemp sesbania is an important weed of rice (Smith 1968) and summer row crops (Woon 1987, Norsworthy and Oliver 2002a).  However, because its diffuse canopy of small leaflets allows passage of light and the profusion of N-fixing nodules on its root system minimize competition for N with the crop, this weed is often less competitive than its rapid growth and great stature would indicate (McWhorter and Anderson 1979).

Hemp sesbania grows best at hot, mid-summer day/night temperatures of 86/77 °F (30/25 °C) or above.  Soybean growth is slowed less by cooler, 77/59 °F (25/15 °C) day/night temperatures, than hemp sesbania (King and Purcell 1997).  Hence, establishing soybean relatively early in the growing season helps give the crop a competitive head start.  Similarly, corn and spring cereals that can germinate and grow at cooler temperatures than are suitable for hemp sesbania can competitively suppress this species.  Since the seeds survive well in undisturbed soil, rotation with sodcrops like alfalfa will only moderately reduce the seed bank.

Since some hemp sesbania seedlings will emerge from below crop planting depths, tine weeders and rotary hoes are only partially effective.  Cultivate shallowly close to the row.  Plants do not usually emerge above the soybean canopy until late July or early August but most competition occurs 4-10 weeks after soybean emergence (McWhorter and Anderson 1979).  Nevertheless, if possible, mow off plants just above the crop canopy shortly after the weed begins to flower to reduce seed production.  The tall height, tough stems and superficial root system probably makes this weed susceptible to mechanical weed pullers in soybean, cotton and some other crops.  Yield loss in soybeans can be reduced by high crop density (e.g., 209,000 plants/A = 517,000 plants/ha) (Norsworthy and Oliver 2002a).  High density planting in rice probably will also help suppress the weed.  Irrigation of soybeans with unmanaged hemp sesbania in Arkansas increased growth and light interception by the weed at the expense of the crop, but still substantially increased crop yield (King and Purcell 1997, Norsworthy and Oliver 2002b).

Since hemp sesbania supports nitrogen fixing symbiotic bacteria, it is relatively independent of soil N for growth.  Hence any N deficiency will competitively favor this weed over the crop.  It produces root exhudates that inhibit soybean nodulation, so N fertilization sometimes helps soybeans compete with this weed (King and Purcell 1997).

Hemp sesbania seeds are likely to be killed by heat produced from narrow-windrow burning of soybean harvest residues (Norsworthy et al. 2020).

Ecology

Origin and distribution: Hemp sesbania is native to the Southeast, southern Midwest, and Southwest U.S.A. (UC SAREP); it occurs south to Central America (Hall et al. 2003) and sporadically northward to southern Ontario (USDA Plants).  It has been introduced into Russia (ILDIS).

Seed weight:  6.0 mg (Bennett and Shaw 2000), 15 mg (Clay and Griffin 2000).

Dormancy and germination: Hemp sesbania seeds have physical dormancy maintained by an impermeable seed coat (Johnston et al. 1979) and at maturity, few seeds will germinate (Egley and Chandler 1983).  Permeable seeds germinate well at temperatures from 58-104 °F (20-40 °C), but germination is negligible at 41 °F (5 °C).  Light neither promotes nor inhibits germination.  Seeds have to take up 58-65% of their weight in water to germinate, and two or more cycles of partial hydration followed by dehydration greatly decrease germinability, probably killing the seeds (Williams 1980).  However, seeds will germinate under greater moisture stress than soybeans (Johnston et al. 1979, Williams 1980).

Seed longevity:  Hemp sesbania seeds persist well in the soil seed bank, with 18% surviving 5.5 years of undisturbed burial (Egley and Chandler 1983), resulting in a computed 27% annual rate of mortality per year.  Nevertheless, when a hemp sesbania seed bank was tilled annually to depths of 2 to 6” (5 to 15 cm), emergence declined by an average of 65% per year over a 4-year period, with slightly faster declines with deeper tillage (Egley and Williams 1990).  Overwinter flooding of fields causes only minor deterioration of seeds (Nelms and Twedt 1996).

Season of emergence:  In Mississippi, seedlings emerged primarily from May through July, with often two distinct periods of emergence (Egley and Williams 1991).  In a series of experiments with soybean planted mid-May to early June, most hemp sesbania emerged simultaneously with the crop (McWhorter and Anderson 1979), and in another experiment 98% of seeds emerge within a 6 week period (Lovelace and Oliver 2000).

Emergence depth:  Hemp sesbania emerges best from 0.4-1.2” (1-3 cm), but a few seedlings can emerge from depths up to 5” (12 cm) (Johnston et al. 1979).  Under favorable conditions, seeds in the top 1.2” (3 cm) of soil can emerge in as little as 2 days, giving the weed a head start over many crops (Johnston et al. 1979).

Photosynthetic pathway: C3

Sensitivity to frost:  Hemp sesbania does not tolerate frost (UC SAREP).

Drought tolerance:  The species grows best in moist conditions, but can tolerate drought once it is well established (UC SAREP).  

Mycorrhizae:  Hemp sesbania is mycorrhizal (Aziz and Sylvia 1995).

Response to fertility:  Hemp sesbania roots form an association with nitrogen fixing rhizobial bacteria (UC SAREP, Vora and Martínez-Romero 2000), and is not responsive to N fertility.  It tolerates pH down to 4.5 and also tolerates alkaline conditions (UC SAREP).

Soil physical requirements:  Hemp sesbania is most troublesome on clay and heavy loam soils (Johnston et al. 1979, McWhorter and Anderson 1979) and grows poorly on sandy soils (Johnston et al. 1979).  Hemp sesbania tolerates flooding and waterlogged soils, so it can be a problem in both rainfed and paddy rice conditions.  It also tolerates salinity and has been used as a green manure for reclaiming saline soils (UC SAREP).

Response to shade:  It is highly intolerant of shade, but if given the opportunity, it grows 10” (3 m) or more in height (UC SAREP) and thus can potentially overtop the tallest of crops.

Sensitivity to disturbance:  Killing plants at initial pod set, defined as 75% blossom drop when pods were <3” (< 8 cm), reduced production of viable seeds by 94% (Clay and Griffin 2000).

Time from emergence to flowering:  Plants flower from June to October (Lorenzi and Jeffery 1987), with flowers appearing about 6-7 weeks after emergence (UC SAREP). The time from initial pod set to seed maturity is about 6 weeks (Clay and Griffin 2000).  Thus, plants emerging in May mature by mid-August.  In California, seed production continues from June to October (UC SAREP), but seed production from a given cohort occurs more or less simultaneously (Clay and Griffin 2000).

Pollination:  Flowers are visited by bees (UGA Entomology), but, as with related species, may be self-pollinated as well (Sajjad et al. 2009).

Reproduction:  Widely spaced plants produced 21,500 seeds/plant (Lovelace and Oliver 2000).  Plants spaced 3 ft (0.9 m) produced 2,100-9,400 seeds/plant (Clay and Griffin 2000).

Dispersal:  Legume seeds with hard seed coats survive digestion in cattle (Gardener et al. 1993), so many seeds that are eaten are likely to disperse in feces or when manure is spread.  Seeds tolerate flooding well (Nelms and Twedt 1996) and probably move in flood water.  The seeds can contaminate crop seed (USDA 2018), and may occasionally be dispersed during disposal of cotton gin trash (Norsworthy et al. 2009).

Common natural enemies:  The anthracnose fungi Colletotrichum truncatum is being developed as a biocontrol agent (Boyette et al. 2007, Boyette and Hoagland 2010).

Palatability:  Hemp sesbania has better digestibility and higher crude protein than common southern forage grasses, but has a higher than optimal Ca:P ratio after flowering  (Bosworth et al. 1980).  Although other species of Sesbania cause irritation of the digestive tract and diarrhea in domestic animals, hemp sesbania has low toxicity.  Nevertheless, 2-3% hemp sesbania seeds in the diet of chickens will reduce food intake and egg production, and 7% creates low level mortality (Burrows and Tyrl 2001).

References:

• Aziz, T., and D. M. Sylvia.  1995.  Activity and species composition of arbuscular mycorrhizal fungi following soil removal.  Ecological Applications 5:776-784.
• Bennett, A. C., and D. R. Shaw.  2000.  Effect of preharvest desiccants on weed seed production and viability.  Weed Technology 14:530-538.
• Bosworth, S. C., C. S. Hoveland, G. A. Buchanan, and W. B. Anthony.  1980.  Forage quality of selected warm-season weed species.  Agronomy Journal 72:1050-1054.
• Boyette, C. D., and R. E. Hoagland.  2010.  Biological control of hemp sesbania (Sesbania exaltata) and sicklepod (Senna obtusifolia) in soybean with anthracnose pathogen mixtures.  Weed Technology 24:551-556.
• Boyette, C. D., R. E. Hoagland, and M. A. Weaver.  2007.  Biocontrol efficacy of Colletotrichum truncatum for hemp sesbania (Sesbania exaltata) is enhanced with unrefined corn oil and surfactant.  Weed Biology and Management 7:70-76.
• Burrows, G. E., and R. J. Tyrl.  2001.  Toxic Plants of North America. Iowa State University Press:Ames, Iowa.
• Clay, P. A, and J. L. Griffin.  2000.  Weed seed production and seedling emergence responses to late-season glyphosate applications.  Weed Science 48:481-486.
• Egley, G. H,. and J. M. Chandler.  1983.  Longevity of weed seeds after 5.5 years in the Stoneville 50-year buried-seed study.  Weed Science 31:264-270.
• Egley, G. H., and R. D. Williams.  1990.  Decline of weed seeds and seedling emergence over five years as affected by soil disturbance.  Weed Science 38:504-510.
• Egley, G. H., and R. D. Williams.  1991.  Emergence periodicity of six summer annual weed species.  Weed Science, 39:595-600.
• Gardener, C. J., J. G. McIvor, and A. Jansen.  1993.  Survival of seeds of tropical grassland species subjected to bovine digestion.  Journal of Applied Ecology 30:75-85.
• Hall, D. W., V. V. Vandiver, and J. A. Ferrell.  2003.  Hemp sesbania (Sesbania exaltata (Raf.) Cory).  University of Florida Institute of Food and Agricultural Sciences, SP37.  http://edis.ifas.ufl.edu/pdffiles/FW/FW03900.pdf
• King, C. A., and L. C. Purcell.  1997.  Interference between hemp sesbania (Sesbania exaltata) and soybean (Glycine max) in response to irrigation and nitrogen.  Weed Science 45:91-97.
• ILDIS.  Sesbania herbacea.  International Legume Database and Information Service.  https://www.ildis.org/
• Johnston, S. K., R. H. Walker, and D. S. Murray.  1979.  Germination and emergence of  hemp sesbania (Sesbania exaltataa).  Weed Science 27:290-293.
• Lorenzi, H., and L. S. Jeffery.  1987.  Weeds of the United States and their control.  Van Nostrand Reinhold: New York.
• Lovelace, M. L., and L. R. Oliver.  2000.  Effects of interference and tillage on hemp sesbania and pitted morningglory emergence, growth, and seed production.  2000. Proceedings of the Southern Weed Science Society 53:202.
• McWhorter, C. G.. and J. M. Anderson.  1979.  Hemp sesbania (Sesbania exalta) competition in soybeans (Glycine max).  Weed Science 27:58-64.
• Nelms, C. O., and D. J. Twedt.  1996.  Seed deterioration in flooded agricultural fields during winter.  Wildlife Society Bulletin 24:85-88.
• Norsworthy, J. K., J. K. Green, T. Barber, T. L. Roberts, and M. J. Walsh.  2020.  Seed destruction of weeds in southern US crops using heat and narrow-windrow burning.  Weed Technology 34:589–596.
• Norsworthy, J. K., and L. R. Oliver.  2002a.  Hemp sesbania interference in drill-seeded glyphosate-resistant soybean.  Weed Science 50:34-41.
• Norsworthy, J. K., and L. R. Oliver.  2002b.  Effect of irrigation, soybean (Glycine max) density and glyphosate on hemp sesbania (Sesbania exaltata) and pitted morningglory (Ipomoea lacunosa).  Weed Technology 16:7-17.
• Norswrothy, J. K., and K. L. Smith, L. E. Steckel, and C. H. Koger.  2009.  Weed seed contamination of cotton gin trash.  Weed Technology 23:574-580.
• Sajjad, A., S. Saeed, W. Muhammad and M. J. Arif.  2009.  Role of insects in cross-pollination and yield attributing components of Sesbania sesban.  International Journal of Agricculture and Biology 11:77–80.
• Smith, R. J. Jr.  1968.  Weed competition in rice.  Weed Science 16:252-255.
• UC SAREP-Sesbania.  University of California Sustainable Agriculture Research and Education Program, Online Cover Crop Database.  Sesbania.  http://asi.ucdavis.edu/programs/sarep/research-initiatives/are/nutrient-mgmt/cover-crops-database1
• UGA Entomology.  Pollination: plants for year-round bee forage.  University of Georgia, College of Agriculture and Environmental Sciences, Department of Entomology, Honey Bee Program.  http://www.ent.uga.edu/bees/pollination/plants-year-round-forage.html
• USDA Plants Database, Natural Resources Conservation Service.  http://plants.usda.gov
• USDA.  2018.  State Noxious-Weed Seed Requirements Recognized In The Administration Of The Federal Seed Act.  https://www.ams.usda.gov/sites/default/files/media/StateNoxiousWeedsSeedList.pdf
• Vora., E. T., and E. Martínez-Romero.  2000.  Sesbania herbacea–Rhizobium huautlense nodulation in flooded soils and comparative characterization of S. herbacea-nodulating Rhizobia in different environments.  Microbial Ecology 41:15-42. 
• Williams, R. D.  1980.  Moisture stress and hydration-dehydration effects on hemp sesbania (Sesbania exalta) seed germination.  Weed Science 28:487-492.
• Woon, C. K.  1987.  Effect of two row spacings and hemp sesbania competiton on sunflower.  Journal of Agronomy and Crop Science 159:15-20