Research directed by C. Daehler (UH Botany) with funding from the Kaulunani Urban Forestry Program and US Forest Service

Information on Risk Assessments
Original risk assessment

Cymbopogon citratus (DC.) Stapf; lemongrass

Answer

1.01

Is the species highly domesticated?

y=-3, n=0

y

1.02

Has the species become naturalized where grown?

y=-1, n=-1

y

1.03

Does the species have weedy races?

y=-1, n=-1

n

2.01

Species suited to tropical or subtropical climate(s) (0-low; 1-intermediate; 2-high) – If island is primarily wet habitat, then substitute “wet tropical” for “tropical or subtropical”

See Append 2

2

2.02

Quality of climate match data (0-low; 1-intermediate; 2-high) see appendix 2

2

2.03

Broad climate suitability (environmental versatility)

y=1, n=0

n

2.04

Native or naturalized in regions with tropical or subtropical climates

y=1, n=0

y

2.05

Does the species have a history of repeated introductions outside its natural range? y=-2

?=-1, n=0

y

3.01

Naturalized beyond native range y = 1*multiplier (see Append 2), n= question 2.05

y

3.02

Garden/amenity/disturbance weed y = 1*multiplier (see Append 2)

n=0

n

3.03

Agricultural/forestry/horticultural weed y = 2*multiplier (see Append 2)

n=0

n

3.04

Environmental weed y = 2*multiplier (see Append 2)

n=0

n

3.05

Congeneric weed y = 1*multiplier (see Append 2)

n=0

y

4.01

Produces spines, thorns or burrs

y=1, n=0

n

4.02

Allelopathic

y=1, n=0

4.03

Parasitic

y=1, n=0

n

4.04

Unpalatable to grazing animals

y=1, n=-1

n

4.05

Toxic to animals

y=1, n=0

n

4.06

Host for recognized pests and pathogens

y=1, n=0

y

4.07

Causes allergies or is otherwise toxic to humans

y=1, n=0

n

4.08

Creates a fire hazard in natural ecosystems

y=1, n=0

4.09

Is a shade tolerant plant at some stage of its life cycle

y=1, n=0

n

4.1

Tolerates a wide range of soil conditions (or limestone conditions if not a volcanic island)

y=1, n=0

y

4.11

Climbing or smothering growth habit

y=1, n=0

n

4.12

Forms dense thickets

y=1, n=0

n

5.01

Aquatic

y=5, n=0

n

5.02

Grass

y=1, n=0

y

5.03

Nitrogen fixing woody plant

y=1, n=0

n

5.04

Geophyte (herbaceous with underground storage organs -- bulbs, corms, or tubers)

y=1, n=0

n

6.01

Evidence of substantial reproductive failure in native habitat

y=1, n=0

6.02

Produces viable seed.

y=1, n=-1

y

6.03

Hybridizes naturally

y=1, n=-1

6.04

Self-compatible or apomictic

y=1, n=-1

n

6.05

Requires specialist pollinators

y=-1, n=0

n

6.06

Reproduction by vegetative fragmentation

y=1, n=-1

n

6.07

Minimum generative time (years) 1 year = 1, 2 or 3 years = 0, 4+ years = -1

See left

7.01

Propagules likely to be dispersed unintentionally (plants growing in heavily trafficked areas)

y=1, n=-1

n

7.02

Propagules dispersed intentionally by people

y=1, n=-1

y

7.03

Propagules likely to disperse as a produce contaminant

y=1, n=-1

n

7.04

Propagules adapted to wind dispersal

y=1, n=-1

7.05

Propagules water dispersed

y=1, n=-1

n

7.06

Propagules bird dispersed

y=1, n=-1

n

7.07

Propagules dispersed by other animals (externally)

y=1, n=-1

n

7.08

Propagules survive passage through the gut

y=1, n=-1

n

8.01

Prolific seed production (>1000/m2)

y=1, n=-1

n

8.02

Evidence that a persistent propagule bank is formed (>1 yr)

y=1, n=-1

8.03

Well controlled by herbicides

y=-1, n=1

8.04

Tolerates, or benefits from, mutilation, cultivation, or fire

y=1, n=-1

y

8.05

Effective natural enemies present locally (e.g. introduced biocontrol agents)

y=-1, n=1

Total score:

-2

Source

Notes

1.01

Origin and geographic distribution The exact origin of Cymbopogon citratus is not known but a Malesian origin is most likely. Cymbopogon citratus is only known from cultivation and it has been cultivated for several centuries in South and South-East Asia.

Oyen, L.P.A., 2002. Cymbopogon citratus (DC.) Stapf [Internet] Record from Proseabase. L.P.A. Oyen and Nguyen Xuan Dung (Editors). PROSEA (Plant Resources of South-East Asia) Foundation, Bogor, Indonesia. http://www.proseanet.org. Accessed from Internet: Thursday, 02 June 2005.

1.02

Lemongrass is now found cultivated and often naturalized throughout the tropics and warm subtropics e.g. in southern parts of the Russian Federation and northern Australia. It is very commonly cultivated throughout South-East Asia both as an industrial and as a garden crop

Oyen, L.P.A., 2002. Cymbopogon citratus (DC.) Stapf [Internet] Record from Proseabase. L.P.A. Oyen and Nguyen Xuan Dung (Editors). PROSEA (Plant Resources of South-East Asia) Foundation, Bogor, Indonesia. http://www.proseanet.org. Accessed from Internet: Thursday, 02 June 2005.

1.03

no evidence

2.01

Origin and geographic distribution The exact origin of Cymbopogon citratus is not known but a Malesian origin is most likely. Cymbopogon citratus is only known from cultivation and it has been cultivated for several centuries in South and South-East Asia.

Oyen, L.P.A., 2002. Cymbopogon citratus (DC.) Stapf [Internet] Record from Proseabase. L.P.A. Oyen and Nguyen Xuan Dung (Editors). PROSEA (Plant Resources of South-East Asia) Foundation, Bogor, Indonesia. http://www.proseanet.org. Accessed from Internet: Thursday, 02 June 2005.

2.02

2.03

Cymbopogon citratus grows best under sunny, warm and humid conditions. It performs best below 500 m altitude, but is grown up to 750 m in Madagascar and the Comoros. Average daytime temperatures of 23—30°C without extremely low night temperatures are optimum for growth and yield. Short periods with a daily maximum temperature over 30°C do not harm growth but severely reduce oil content. Hot dry winds may not only desiccate the crop but can also evaporate the oil. Frost is normally fatal.

Oyen, L.P.A., 2002. Cymbopogon citratus (DC.) Stapf [Internet] Record from Proseabase. L.P.A. Oyen and Nguyen Xuan Dung (Editors). PROSEA (Plant Resources of South-East Asia) Foundation, Bogor, Indonesia. http://www.proseanet.org. Accessed from Internet: Thursday, 02 June 2005.

2.04

Origin and geographic distribution The exact origin of Cymbopogon citratus is not known but a Malesian origin is most likely. Cymbopogon citratus is only known from cultivation and it has been cultivated for several centuries in South and South-East Asia.

Oyen, L.P.A., 2002. Cymbopogon citratus (DC.) Stapf [Internet] Record from Proseabase. L.P.A. Oyen and Nguyen Xuan Dung (Editors). PROSEA (Plant Resources of South-East Asia) Foundation, Bogor, Indonesia. http://www.proseanet.org. Accessed from Internet: Thursday, 02 June 2005.

2.05

Lemongrass is now found cultivated and often naturalized throughout the tropics and warm subtropics e.g. in southern parts of the Russian Federation and northern Australia. It is very commonly cultivated throughout South-East Asia both as an industrial and as a garden crop

Oyen, L.P.A., 2002. Cymbopogon citratus (DC.) Stapf [Internet] Record from Proseabase. L.P.A. Oyen and Nguyen Xuan Dung (Editors). PROSEA (Plant Resources of South-East Asia) Foundation, Bogor, Indonesia. http://www.proseanet.org. Accessed from Internet: Thursday, 02 June 2005.

3.01

Lemongrass is now found cultivated and often naturalized throughout the tropics and warm subtropics e.g. in southern parts of the Russian Federation and northern Australia. It is very commonly cultivated throughout South-East Asia both as an industrial and as a garden crop

Oyen, L.P.A., 2002. Cymbopogon citratus (DC.) Stapf [Internet] Record from Proseabase. L.P.A. Oyen and Nguyen Xuan Dung (Editors). PROSEA (Plant Resources of South-East Asia) Foundation, Bogor, Indonesia. http://www.proseanet.org. Accessed from Internet: Thursday, 02 June 2005.

3.02

it stays together in a clump, and because of this behavior it is not substantially invasive

http://www.phoenixtropicals.com/lemon_grass.html

3.03

no evidence

3.04

no evidence

3.05

Cymbopogon nardus is an unpalatable, unwanted invader of Ankole district pastures in Uganda. Removal of C. nardus from fully stocked pastures improved growth rates by about 30 percent, but the rate of recolonization can be extremely rapid.

http://www.fao.org/ag/AGP/AGPC/doc/GBASE/DATA/PF000206.HTM

4.01

leaves have sharp edges and can inflict razor cuts on the unwary

http://www.floridata.com/ref/C/cymb_cit.cfm

4.02

"A. absinthium and C. citratus possess strong allelopathic inhibitory effects on B. pilosa" [lab results using plant extracts; no evididence from field or natural situations]

Allelopathic effect of Cymbopogon citratus and Artemisia absinthium on seeds of Bidens pilosa. / Efeito alelopatico de Cymbopogon citratus e Artemisia absinthium sobre sementes de Bidens pilosa By: Cruz, M. E. S.; Acta Horticulturae (569), 2002, p.229-233

4.03

no evidence

4.04

Spent grass mixed with bagasse and made into silage is a common cattle feed in lemongrass-producing areas.

Oyen, L.P.A., 2002. Cymbopogon citratus (DC.) Stapf [Internet] Record from Proseabase. L.P.A. Oyen and Nguyen Xuan Dung (Editors). PROSEA (Plant Resources of South-East Asia) Foundation, Bogor, Indonesia. http://www.proseanet.org. Accessed from Internet: Thursday, 02 June 2005.

4.05

enjoyed by dogs

http://www.floridata.com/ref/C/cymb_cit.cfm

4.06

Puccinia purpurea (Sorghum rust) is a specialist pathogen which also infect other crop species in Poaceae

Farr, D.F., Rossman, A.Y., Palm, M.E., & McCray, E.B. (n.d.) Fungal Databases, Systematic Botany & Mycology Laboratory, ARS, USDA. Retrieved June 2, 2005, from http://nt.ars-grin.gov/fungaldatabases/

4.07

Abstract: Allergic contact dermatitis from the topical use of essential oils is not widely recognized as an occupational hazard. Four cases of allergic contact dermatitis to essential oils occurring in three aromatherapists and one chemist with a particular interest in aromatherapy are described. All presented with predominantly hand dermatitis and demonstrated sensitization to multiple essential oils. One patient developed a recurrence of cutaneous symptoms following ingestion of lemongrass tea. Workers within this industry should be aware of the sensitization potential of these products and the risk of limiting their ability to continue employment. [seem to be rare cases only]

Allergic contact dermatitis following exposure to essential oils. By: Bleasel, N.; Australasian Journal of Dermatology 43 (3), 2002, p.211-213

4.08

[grass leaves are flammable, but no evidence that it grows at high densities in nature]

http://www.floridata.com/ref/C/cymb_cit.cfm

4.09

(1)Light: Bright sun preferred but will grow in light shade. (2)full sun / light shade [references only to "light" shade]

(1)http://www.floridata.com/ref/C/cymb_cit.cfm (2)www.tropilab.com/lemon-gras.html

4.1

Good drainage is the most important soil requirement for Cymbopogon citratus and in many countries plantations are on sandy soils, though loamy soils are used e.g. in China, Madagascar and Vietnam. Generally, soils of Cymbopogon citratus plantations have a pH of 5.5—7.5, although good growth has been observed in Australia on a clay soil with pH 9.6. Good growth was also found on acid peat soils in Sarawak, Malaysia (pH 4.5). Saline soils are considered unsuitable, although fair growth and oil yield on saline soils have been obtained in greenhouse experiments.

Oyen, L.P.A., 2002. Cymbopogon citratus (DC.) Stapf [Internet] Record from Proseabase. L.P.A. Oyen and Nguyen Xuan Dung (Editors). PROSEA (Plant Resources of South-East Asia) Foundation, Bogor, Indonesia. http://www.proseanet.org. Accessed from Internet: Thursday, 02 June 2005.

4.11

Description: Perennial, tufted, aromatic grass with numerous erect culms arising from a short, oblique, ring-shaped, sparingly branched rhizome.

Oyen, L.P.A., 2002. Cymbopogon citratus (DC.) Stapf [Internet] Record from Proseabase. L.P.A. Oyen and Nguyen Xuan Dung (Editors). PROSEA (Plant Resources of South-East Asia) Foundation, Bogor, Indonesia. http://www.proseanet.org. Accessed from Internet: Thursday, 02 June 2005.

4.12

Perennial, tufted, aromatic grass with numerous erect culms arising from a short, oblique, ring-shaped, sparingly branched rhizome. Culm (stem) up to 2(—3) m tall, solid below, pruinose below the nodes, smooth and glabrous.

Oyen, L.P.A., 2002. Cymbopogon citratus (DC.) Stapf [Internet] Record from Proseabase. L.P.A. Oyen and Nguyen Xuan Dung (Editors). PROSEA (Plant Resources of South-East Asia) Foundation, Bogor, Indonesia. http://www.proseanet.org. Accessed from Internet: Thursday, 02 June 2005.

5.01

terrestrial

5.02

Description: Perennial, tufted, aromatic grass

Oyen, L.P.A., 2002. Cymbopogon citratus (DC.) Stapf [Internet] Record from Proseabase. L.P.A. Oyen and Nguyen Xuan Dung (Editors). PROSEA (Plant Resources of South-East Asia) Foundation, Bogor, Indonesia. http://www.proseanet.org. Accessed from Internet: Thursday, 02 June 2005.

5.03

no evidence

5.04

no description of these traits

Oyen, L.P.A., 2002. Cymbopogon citratus (DC.) Stapf [Internet] Record from Proseabase. L.P.A. Oyen and Nguyen Xuan Dung (Editors). PROSEA (Plant Resources of South-East Asia) Foundation, Bogor, Indonesia. http://www.proseanet.org. Accessed from Internet: Thursday, 02 June 2005.

6.01

As Cymbopogon citratus only rarely produces seed it is usually propagated vegetatively. In most places Cymbopogon citratus flowers very rarely or not at all. Plants usually do not become older than 4—6 years. [status in native range unknown]

Oyen, L.P.A., 2002. Cymbopogon citratus (DC.) Stapf [Internet] Record from Proseabase. L.P.A. Oyen and Nguyen Xuan Dung (Editors). PROSEA (Plant Resources of South-East Asia) Foundation, Bogor, Indonesia. http://www.proseanet.org. Accessed from Internet: Thursday, 02 June 2005.

6.02

Propagation: By division of old clumps in the spring and summer. Also by seed which is not readily available.

http://www.floridata.com/ref/C/cymb_cit.cfm

6.03

no evidence

6.04

Abstract: Work at the Chipo experimental station has included the selection of numerous clones of Cymbopogon citratus, C. flexuosus and C. nardus varying in agronomic and chemical characteristics. Evidence that the species are cross pollinating and self sterile has been obtained

Report on the grass-breeding expert mission to the Association of Essential Oil Producers in Guatemala from 1 to 30 March, 1974. / Bericht uber die Expertentatigkeit auf dem Gebiete der Graserzuchtung bei der Asociacion de Productores de Aceites Esenciales (Produktionsgemeinschaft fur die Erzeugung atherischer Ole) in Guatemala vom 1. bis 30. Marz 1974 By: Ruckenbauer, P.; Bodenkultur 26 (1), 1975, p.99-109

6.05

no evidence

6.06

Grass grows as tight clumps [not naturally spreading from fragmentation]

http://www.floridata.com/ref/C/cymb_cit.cfm

6.07

Plants usually do not become older than 4—6 years. [does not normally reproduce by seeds]

Oyen, L.P.A., 2002. Cymbopogon citratus (DC.) Stapf [Internet] Record from Proseabase. L.P.A. Oyen and Nguyen Xuan Dung (Editors). PROSEA (Plant Resources of South-East Asia) Foundation, Bogor, Indonesia. http://www.proseanet.org. Accessed from Internet: Thursday, 02 June 2005.

7.01

no evidence

7.02

Lemongrass is now found cultivated and often naturalized throughout the tropics and warm subtropics e.g. in southern parts of the Russian Federation and northern Australia. It is very commonly cultivated throughout South-East Asia both as an industrial and as a garden crop

Oyen, L.P.A., 2002. Cymbopogon citratus (DC.) Stapf [Internet] Record from Proseabase. L.P.A. Oyen and Nguyen Xuan Dung (Editors). PROSEA (Plant Resources of South-East Asia) Foundation, Bogor, Indonesia. http://www.proseanet.org. Accessed from Internet: Thursday, 02 June 2005.

7.03

no evidence

7.04

the 1000-grain weight is only 80-120 mg. [small seeds, but seeds rarely produced]

Report on the grass-breeding expert mission to the Association of Essential Oil Producers in Guatemala from 1 to 30 March, 1974. / Bericht uber die Expertentatigkeit auf dem Gebiete der Graserzuchtung bei der Asociacion de Productores de Aceites Esenciales (Produktionsgemeinschaft fur die Erzeugung atherischer Ole) in Guatemala vom 1. bis 30. Marz 1974 By: Ruckenbauer, P.; Bodenkultur 26 (1), 1975, p.99-109

7.05

no evidence

7.06

no evidence

7.07

no evidence

7.08

no evidence

8.01

Cymbopogon citratus only rarely produces seed

Oyen, L.P.A., 2002. Cymbopogon citratus (DC.) Stapf [Internet] Record from Proseabase. L.P.A. Oyen and Nguyen Xuan Dung (Editors). PROSEA (Plant Resources of South-East Asia) Foundation, Bogor, Indonesia. http://www.proseanet.org. Accessed from Internet: Thursday, 02 June 2005.

8.02

no evidence

8.03

no evidence

8.04

First harvest of leaves of lemongrass may start about 6—8 months after planting. Subsequently leaves can be cut 3—6 times per year during 4—6 years. In South America the cutting cycle is generally maintained at 3—4 months, which is believed to promote tillering and leaf yield. [tolerate periodic harvest practice]

Oyen, L.P.A., 2002. Cymbopogon citratus (DC.) Stapf [Internet] Record from Proseabase. L.P.A. Oyen and Nguyen Xuan Dung (Editors). PROSEA (Plant Resources of South-East Asia) Foundation, Bogor, Indonesia. http://www.proseanet.org. Accessed from Internet: Thursday, 02 June 2005.

8.05

no evidence