Pacific Island Ecosystems at Risk (PIER)


Senna spectabilis


RISK ASSESSMENT RESULTS: High risk, score: 11


Australian/New Zealand Weed Risk Assessment adapted for Hawai‘i.
Information on Risk Assessments
Original risk assessment

Senna spectabilis (DC.) Irwin & Barneby. Family - Fabaceae. Common Names(s) - Spectacular Cassia, casia amarilla . Synonym(s) - Cassia spectabilis DC.

Answer

Score

1.01

Is the species highly domesticated?

y=-3, n=0

n

0

1.02

Has the species become naturalized where grown?

y=1, n=-1

1.03

Does the species have weedy races?

y=-1, n=-1

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

0

2.04

Native or naturalized in regions with tropical or subtropical climates

y=1, n=0

y

1

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

2

3.02

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

n=0

3.03

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

n=0

3.04

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

n=0

y

4

3.05

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

n=0

y

2

4.01

Produces spines, thorns or burrs

y=1, n=0

n

0

4.02

Allelopathic

y=1, n=0

n

0

4.03

Parasitic

y=1, n=0

n

0

4.04

Unpalatable to grazing animals

y=1, n=-1

4.05

Toxic to animals

y=1, n=0

n

0

4.06

Host for recognized pests and pathogens

y=1, n=0

n

0

4.07

Causes allergies or is otherwise toxic to humans

y=1, n=0

n

0

4.08

Creates a fire hazard in natural ecosystems

y=1, n=0

n

0

4.09

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

y=1, n=0

n

0

4.10

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

y=1, n=0

y

1

4.11

Climbing or smothering growth habit

y=1, n=0

n

0

4.12

Forms dense thickets

y=1, n=0

y

1

5.01

Aquatic

y=5, n=0

n

0

5.02

Grass

y=1, n=0

n

0

5.03

Nitrogen fixing woody plant

y=1, n=0

n

0

5.04

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

y=1, n=0

n

0

6.01

Evidence of substantial reproductive failure in native habitat

y=1, n=0

n

0

6.02

Produces viable seed.

y=1, n=-1

y

1

6.03

Hybridizes naturally

y=1, n=-1

6.04

Self-compatible or apomictic

y=1, n=-1

6.05

Requires specialist pollinators

y=-1, n=0

n

0

6.06

Reproduction by vegetative fragmentation

y=1, n=-1

n

-1

6.07

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

See left

2

0

7.01

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

y=1, n=-1

y

1

7.02

Propagules dispersed intentionally by people

y=1, n=-1

y

1

7.03

Propagules likely to disperse as a produce contaminant

y=1, n=-1

n

-1

7.04

Propagules adapted to wind dispersal

y=1, n=-1

n

-1

7.05

Propagules water dispersed

y=1, n=-1

y

1

7.06

Propagules bird dispersed

y=1, n=-1

n

-1

7.07

Propagules dispersed by other animals (externally)

y=1, n=-1

n

-1

7.08

Propagules survive passage through the gut

y=1, n=-1

8.01

Prolific seed production (>1000/m2)

y=1, n=-1

8.02

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

y=1, n=-1

y

1

8.03

Well controlled by herbicides

y=-1, n=1

y

-1

8.04

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

y=1, n=-1

y

1

8.05

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

y=-1, n=1

Total score:

11

Supporting data:

Notes

Source

1.01

(1)No evidence

(1)CAB International, 2005. Forestry Compendium. Wallingford, UK: CAB International.

1.02

1.03

2.01

(1)Senna spectabilis is an attractive small- to medium-sized (to about 10 m tall) multi-stemmed tree, native to Central and South America and naturalized in many other parts of the humid tropics, particularly the Philippines and East and southern Africa.

(1)CAB International, 2005. Forestry Compendium. Wallingford, UK: CAB International.

2.02

(1)Native range well known.

(1)CAB International, 2005. Forestry Compendium. Wallingford, UK: CAB International.

2.03

(1)USDA hardiness zones: 10B through 11 (2)Climatic amplitude (estimates)
- Altitude range: 900 - 1900 m
- Mean annual rainfall: 800 - 2000 mm
- Rainfall regime: bimodal; uniform
- Dry season duration: 1 - 3 months
- Mean annual temperature: 19 - 22ºC
- Mean maximum temperature of hottest month: 23 - 32ºC
- Mean minimum temperature of coldest month: 14 - 17ºC
- Absolute minimum temperature: > 10ºC

(1)http://hort.ufl.edu/trees/SENSPEA.pdf [Accessed 09 Dec 2008] (2)CAB International, 2005. Forestry Compendium. Wallingford, UK: CAB International.

2.04

(1)Senna spectabilis is an attractive small- to medium-sized (to about 10 m tall) multi-stemmed tree, native to Central and South America and naturalized in many other parts of the humid tropics, particularly the Philippines and East and southern Africa.

(1)CAB International, 2005. Forestry Compendium. Wallingford, UK: CAB International.

2.05

(1)Asia Philippines planted
Africa East Africa planted
Southern Africa planted

(1)CAB International, 2005. Forestry Compendium. Wallingford, UK: CAB International.

3.01

(1)Senna spectabilis is an attractive small- to medium-sized (to about 10 m tall) multi-stemmed tree, native to Central and South America and naturalized in many other parts of the humid tropics, particularly the Philippines and East and southern Africa. (2)naturalized in Puerto Rico

(1)CAB International, 2005. Forestry Compendium. Wallingford, UK: CAB International. (2)Liogier, A.H., B. Alain and L. F. Martorell. 2000. Flora of Puerto Rico and adjacent islands: A Systematic Synopsis. Editorial UPR. San Juan, Puerto Rico.

3.02

(1)Weedy in moist conditions [Answered "Yes" to Question 3.04] .

(1)Llamas, K.A. 2003. Tropical Flowering Plants: A Guide to Identification and Cultivation. Timber Press. Portland, OR.

3.03

(1)This agroforestry species acts as a highly effective weed species and has traits that maximize its ability to compete with cash crops. Promotion of S. spectabilis based on tremendous biomass production potential was an insufficient criterion and may have been based on performance-on-research station trials, where soils of high organic matter may not have been representative of smallholder farm environments. Biological review of S. spectabilis and testing on farms revealed the highly competitive nature of this species and its unsuitability as an intercrop species [negative effects on agriculture when purposely planted, but not truly a "weed" of agriculture]

(1)Snapp, S.S. and B. Pound. 2008. Agricultural Systems: Agroecology and Rural Innovation for Development. Academic Press. Burlington, Massachusetts.

3.04

(1)Abstract: Senna spectabilis is a tree native to South and Central America. Thirty-five years ago, it invaded the Mahale Mountains National Park in western Tanzania where it presently covers approximately 225 ha. We quantified its occurrence relative to that of sympatric species of native trees, and compared girdling and felling as methods for its control in three 0.25 ha plots. Within invaded areas of forest, this exotic species was both the most abundant and dominant of the 26 species of tree recorded. During 4 years of monitoring the experimental plots the abundance of S. spectabilis declined markedly in the plots where control methods were practised, but increased slightly in the unmanipulated plot. In contrast, the abundance of native tree species increased markedly in the plots where S. spectabilis had been removed or killed, with higher densities in the girdled rather than the felled plot. S. spectabilis appears to suppress the recruitment of native trees in the Park, and its removal can encourage regeneration of the degraded forest without the need for artificial seeding. (2)Its rapid regeneration and growth make it a potential weed. (3)Due to its high rate of spreading, it has the potential of becoming a danger to the environment. (4)Senna Spectabilis. Its threatening the bio-diversity of the forest. (5)Over the next few years, we’re going to see a rush of activities aimed at combating the eight major invasive species being tackled: water hyacinth, paper mulberry (Broussonetia papyrifera), parthenium weed (Parthenium hysterophorus), citronella (Cymbopogon nardus), mesquite (Prosopis juliflora), Mimosa pigra, Lantana camara, and Senna spectabilis. (6)In Uganda, about 82,530 hectares of Budongo Reserve Forest have been affected by cassia, Senna spectabilis. The plant, that was originally introduced as a boundary marker, has since spread to other parts of the forest. Because of its invasive nature, the tree has been classified as one of the 'weed trees' and suggestions are being made to destroy it in favour of the other 'valuable' timber species.

(1)Wakibara, J. V. and B. J. Mnaya. 2002. Possible control of Senna spectabilis (Caesalpiniaceae), an invasive tree in Mahale Mountains National Park, Tanzania. Oryx 36(4): 357-363. (2)CAB International, 2005. Forestry Compendium. Wallingford, UK: CAB International. (3)Anonymous. 2006. SOCIO-ECONOMIC SEMINAR ON THE SENNA SPECTABILIS. Nyabyeya Forestry College, 25 October 2006. (4)http://www.invasivespecies.co.ug/gallery2.htm [Accessed 09 Dec 2008] (5)Chege, F. 2007. Weeding out invasive species in Africa. CABI News, Issue 2 / Sept 2007. Available from http://www.cabi.org/datapage.asp?iDocID=859 [Accessed 09 Dec 2008] (6)http://www.beluga.is/default.asp?Page=401 [Ac

3.05

(1)S. alata, S. bicapsularis, S. didymobotrya, S. obtusifolia & S. pendula listed as weeds of natural areas.

(1)Weber, E. 2003. Invasive Plant Species of the World. CABI Publishing. Wallingford, UK.

4.01

(1)Cassia is a medium to large tree from tropical America and reaches 60 feet in height, but is often much smaller (Fig. 1). The pinnately compound leaflets have fuzzy undersides and are three inches long.

(1)http://hort.ufl.edu/trees/SENSPEA.pdf [Accessed 09 Dec 2008]

4.02

(1)Abstract An intercrop of maize and cassava was cultivated for six consecutive years from 1990/91 to 1995/96. This paper reports on crop performance from the fourth to the sixth year in alley cropping with Senna spectabilis and in a no-tree control, with and without tillage. Maize grain yield increased significantly from 1993 to 1994 (P = 0.0032) and from 1994 to 1995 (P = 0.019). Tillage only had a significantly positive effect on maize grain yield in 1993. Alley cropping had no significant effect on maize grain yield in any year. Cassava root yield was neither affected by tillage nor by alley cropping in any year. Neither the cumulative yields over the three years nor the sum of maize grain and cassava root yield were significantly affected by alley cropping or tillage. No significant interactions were found between cropping system and tillage system. [no allelopathic effects] (2)This agroforestry species acts as a highly effective weed species and has traits that maximize its ability to compete with cash crops. Promotion of S. spectabilis based on tremendous biomass production potential was an insufficient criterion and may have been based on performance-on-research station trials, where soils of high organic matter may not have been representative of smallholder farm environments. Biological review of S. spectabilis and testing on farm revealed the highly competitive nature of this species and ts unsuitability as an intercrop species. [not allelopathic but competitive ability makes it unsuitable for growth with crops]

(1)Hauser, S., J. N. Ndi and N. R. Hulugalle. 2000. Performance of a maize/cassava intercrop in tilled and no-till Senna spectabilis alley cropping on an Ultisol in southern Cameroon. Agroforestry Systems 49(2): 177-188. (2)Snapp, S.S. and B. Pound. 2008. Agricultural Systems: Agroecology and Rural Innovation for Development. Academic Press. Burlington, Massachusetts.

4.03

(1)No evidence

(1)CAB International, 2005. Forestry Compendium. Wallingford, UK: CAB International.

4.04

(1)Although a legume, it is not a nitrogen-fixing species but is nevertheless useful for fodder, mulches, and as a honey source [reference 1 & 2 are contradictory (2)It is also largely unpalatable to forest animals including chimpanzees who are the subject of high profile conservation efforts.

(1)CAB International, 2005. Forestry Compendium. Wallingford, UK: CAB International. (2)NARO 2004. Implementation of invasive plant prevention and control programmes in Uganda. Report submitted to the CAB International Africa Regional Centre under the PDF-B phase of the UNEP/GEF Project: Removing Barriers to Invasive Plant Management in Africa. National Agricultural Research Organisation, Entebbe, Uganda.

4.05

(1)Although a legume, it is not a nitrogen-fixing species but is nevertheless useful for fodder, mulches, and as a honey source [no evidence and used as fodder]

(1)CAB International, 2005. Forestry Compendium. Wallingford, UK: CAB International.

4.06

(1)Pest resistance: long-term health usually not affected by pests...No pests or diseases of major concern. (2) It is reported to be easier to raise, less susceptible to pests and diseases, and more drought-resistant than Senna siamea.

(1)http://hort.ufl.edu/trees/SENSPEA.pdf [Accessed 09 Dec 2008] (2)CAB International, 2005. Forestry Compendium. Wallingford, UK: CAB International.

4.07

(1)No evidence

(1)CAB International, 2005. Forestry Compendium. Wallingford, UK: CAB International.

4.08

(1) It is a fast-growing species, particularly on deep soils, and is fire- and termite-resistant and tolerant of strongly acid soils.

(1)CAB International, 2005. Forestry Compendium. Wallingford, UK: CAB International.

4.09

(1)Light requirement: tree grows in full sun (2)Sun Exposure: Full sun

(1)http://hort.ufl.edu/trees/SENSPEA.pdf [Accessed 09 Dec 2008] (2)http://www.desert-tropicals.com/Plants/Fabaceae/Cassia_spectabilis.html [Accessed 09 Dec 2008]

4.10

(1)Soil tolerances: clay; loam; sand; slightly alkaline; acidic; well-drained (2)Soil descriptors
- Soil texture: medium; heavy
- Soil drainage: free
- Soil reaction: very acid; acid; neutral
- Special soil tolerances: shallow
- Soil types: vertisols; ferralsols; fluvisols; nitisols

(1)http://hort.ufl.edu/trees/SENSPEA.pdf [Accessed 09 Dec 2008] (2)CAB International, 2005. Forestry Compendium. Wallingford, UK: CAB International.

4.11

(1)Cassia is a medium to large tree from tropical America and reaches 60 feet in height, but is often much smaller (Fig. 1). The pinnately compound leaflets have fuzzy undersides and are three inches long.

(1)http://hort.ufl.edu/trees/SENSPEA.pdf [Accessed 09 Dec 2008]

4.12

(1)It is common mainly along logging trails/landing sites in the Budongo Forest, where it forms pure stands at the expense of other species.

(1)NARO 2004. Implementation of invasive plant prevention and control programmes in Uganda. Report submitted to the CAB International Africa Regional Centre under the PDF-B phase of the UNEP/GEF Project: Removing Barriers to Invasive Plant Management in Africa. National Agricultural Research Organisation, Entebbe, Uganda.

5.01

(1)Terrestrial

(1)http://hort.ufl.edu/trees/SENSPEA.pdf [Accessed 09 Dec 2008]

5.02

(1)Fabaceae

(1)http://hort.ufl.edu/trees/SENSPEA.pdf [Accessed 09 Dec 2008]

5.03

(1)Although a legume, it is not a nitrogen-fixing species

(1)CAB International, 2005. Forestry Compendium. Wallingford, UK: CAB International.

5.04

(1)No evidence

(1)CAB International, 2005. Forestry Compendium. Wallingford, UK: CAB International.

6.01

(1)No evidence

(1)CAB International, 2005. Forestry Compendium. Wallingford, UK: CAB International.

6.02

(1)Propagation is by seed.

(1)http://hort.ufl.edu/trees/SENSPEA.pdf [Accessed 09 Dec 2008]

6.03

Unknown

6.04

Unknown

6.05

(1)It flowers all the time. Therefore its good for pollination (attracts bees). [floral structure entomophilous]

(1)Anonymous. 2006. SOCIO-ECONOMIC SEMINAR ON THE SENNA SPECTABILIS. Nyabyeya Forestry College, 25 October 2006.

6.06

(1)Vegetative propagation by cuttings [no evidence of vegetative spread, but coppices freely…see Question 8.04]

(1)CAB International, 2005. Forestry Compendium. Wallingford, UK: CAB International.

6.07

(1)Growth rate: fast (2)Senna is extremely fast-growing and flowers and sets seed precociously and profusely.

(1)http://hort.ufl.edu/trees/SENSPEA.pdf [Accessed 09 Dec 2008] (2)NARO 2004. Implementation of invasive plant prevention and control programmes in Uganda. Report submitted to the CAB International Africa Regional Centre under the PDF-B phase of the UNEP/GEF Project: Removing Barriers to Invasive Plant Management in Africa. National Agricultural Research Organisation, Entebbe, Uganda.

7.01

(1)S. Spectabilis seeds were probably picked in the mud and carried into Budongo Forest by trucks from and to the saw mills established in the forest in the late 1950s. As further evidence to this theory, today the S. Spectabilis trees are concentrated along the management roads.

(1)Anonymous. 2006. SOCIO-ECONOMIC SEMINAR ON THE SENNA SPECTABILIS. Nyabyeya Forestry College, 25 October 2006.

7.02

(1)Outstanding tree: tree has outstanding ornamental features and could be planted more (2)It is often planted for fuelwood, as an ornamental and as a shade tree in agroforestry situations.

(1)http://hort.ufl.edu/trees/SENSPEA.pdf [Accessed 09 Dec 2008] (2)CAB International, 2005. Forestry Compendium. Wallingford, UK: CAB International.

7.03

(1)No evidence that seeds are spread as a produce contaminant

(1)NARO 2004. Implementation of invasive plant prevention and control programmes in Uganda. Report submitted to the CAB International Africa Regional Centre under the PDF-B phase of the UNEP/GEF Project: Removing Barriers to Invasive Plant Management in Africa. National Agricultural Research Organisation, Entebbe, Uganda.

7.04

(1)It does not appear to establish under full canopy forest nor do its seeds seem to be dispersed over long distances. (2)seeds 50–70, suborbicular, ca. 5 mm in diam.

(1)NARO 2004. Implementation of invasive plant prevention and control programmes in Uganda. Report submitted to the CAB International Africa Regional Centre under the PDF-B phase of the UNEP/GEF Project: Removing Barriers to Invasive Plant Management in Africa. National Agricultural Research Organisation, Entebbe, Uganda. (2)http://hua.huh.harvard.edu/china/mss/volume10/Fabaceae-AGH-Caesalpinioideae_coauthoring.htm [Accessed 09 Dec 2008]

7.05

(1)S. Spectabilis produces large quantities of seed that do not die easily and therefore spreads fast. When the pod falls down, it bursts and the seeds are easily dispersed by water. In addition the roots are known to germinate and the tree also coppices when cut down.

(1)Anonymous. 2006. SOCIO-ECONOMIC SEMINAR ON THE SENNA SPECTABILIS. Nyabyeya Forestry College, 25 October 2006.

7.06

(1)Fruit characteristics: does not attract wildlife; inconspicuous and not showy; no significant litter problem; persistent on the tree

(1)http://hort.ufl.edu/trees/SENSPEA.pdf [Accessed 09 Dec 2008]

7.07

(1)Fruit characteristics: does not attract wildlife; inconspicuous and not showy; no significant litter problem; persistent on the tree [no means of external attachment]

(1)http://hort.ufl.edu/trees/SENSPEA.pdf [Accessed 09 Dec 2008]

7.08

Unknown if viable seeds can be spread by cattle in droppings

8.01

(1)Cassia is a medium to large tree from tropical America and reaches 60 feet in height, but is often much smaller [probably does not achieve such high seed densities, but numbers unknown]

(1)http://hort.ufl.edu/trees/SENSPEA.pdf [Accessed 09 Dec 2008]

8.02

(1)Propagation: Seeds (must be scarified) (2)Seed storage orthodox (3)Seeds remain viable for up to three years

(1)http://www.desert-tropicals.com/Plants/Fabaceae/Cassia_spectabilis.html [Accessed 09 Dec 2008] (2)CAB International, 2005. Forestry Compendium. Wallingford, UK: CAB International. (3)NARO 2004. Implementation of invasive plant prevention and control programmes in Uganda. Report submitted to the CAB International Africa Regional Centre under the PDF-B phase of the UNEP/GEF Project: Removing Barriers to Invasive Plant Management in Africa. National Agricultural Research Organisation, Entebbe, Uganda.

8.03

(1)Mechanical control methods should be considered backed by appropriate studies. Arboricides are likely to be a more efficient option. However, there is concern about their possible negative environmental effects. (2)Several Senna species effectively controlled by various herbicides.

(1)NARO 2004. Implementation of invasive plant prevention and control programmes in Uganda. Report submitted to the CAB International Africa Regional Centre under the PDF-B phase of the UNEP/GEF Project: Removing Barriers to Invasive Plant Management in Africa. National Agricultural Research Organisation, Entebbe, Uganda. (2)Weber, E. 2003. Invasive Plant Species of the World. CABI Publishing. Wallingford, UK.

8.04

(1)Silvicultural characteristics descriptors

- Tolerates drought; fire

- Ability to coppice; pollard...Its rapid regeneration and growth make it a potential weed. (2)In addition the roots are known to germinate and the tree also coppices when cut down.

(1)CAB International, 2005. Forestry Compendium. Wallingford, UK: CAB International. (2)Anonymous. 2006. SOCIO-ECONOMIC SEMINAR ON THE SENNA SPECTABILIS. Nyabyeya Forestry College, 25 October 2006.

8.05

Unknown


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