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Scientific Name
Synonyms
Common Names
Family
Origin
Naturalised Distribution
Cultivation
Habitat
Distinguishing Features
Habit
Stems and Leaves
Flowers and Fruit
Reproduction and Dispersal
Impacts
Similar Species
Legislation
Sources
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Click on images to enlarge


habit (Photo: Sheldon Navie)


habit in flower (Photo: Sheldon Navie)


habit in fruit (Photo: Sheldon Navie)


once-compound leaves with several pairs of leaflets (Photo: Sheldon Navie)


stem and leaf showing small conical glands between each pair of leaflets (Photo: Sheldon Navie)


close-up of leaflets with pointed tips (Photo: Sheldon Navie)


flower cluster (Photo: Sheldon Navie)


close-up of flowers (Photo: Sheldon Navie)


flower buds and young fruit (Photo: Sheldon Navie)


immature fruit (Photo: Sheldon Navie)


mature fruit (Photo: Sheldon Navie)


close-up of seeds (Photo: Tracey Slotta at USDA PLANTS Database)

Smooth senna
Senna septemtrionalis

Scientific Name

Senna septemtrionalis (Viv.) H.S. Irwin & Barneby

Synonyms

Cassia corymbosa Lam. (misapplied)
Cassia floribunda Cav. (misapplied)
Cassia laevigata Willd.
Cassia septemtrionalis Viv.
Senna x floribunda (Cav.) H.S. Irwin & Barneby (misapplied)

Common Names

arsenic bush, Brazilian buttercup, buttercup bush, Dooleyweed, laburnum, senna, smooth leaved senna, smooth senna, yellow shower

Family

Caesalpiniaceae (Queensland, the ACT, Victoria, Tasmania, Western Australia and the Northern Territory)
Fabaceae: sub-family  Caesalpinioideae (New South Wales)
Leguminosae (South Australia)

Origin

Native to Mexico and Central America (i.e. northern Costa Rica, Guatemala, Honduras and Nicaragua).

Naturalised Distribution

Widely naturalised in eastern Australia (i.e. in eastern Queensland and the coastal districts of New South Wales). Also naturalised on Lord Howe Island and Norfolk Island, and possibly naturalised in Victoria.

Cultivation

This species has escaped cultivation as a garden ornamental, though it is generally rarely if ever deliberately cultivated anymore.

Habitat

A weed of moist forests, rainforests and riparian vegetation in tropical, sub-tropical and warmer temperate regions. It is also occasionally found in open woodlands, along roadsides, and in disturbed sites and waste areas.

Distinguishing Features

Habit

Usually a shrub growing 1-3 m tall, but occasionally a small tree reaching up to 5 m or more in height.

Stems and Leaves

The once-compound (i.e. pinnate) leaves are hairless (i.e. glabrous) and alternately arranged along the stems. These leaves (6-10.5 cm long) are borne on stalks (i.e. petioles) 15-35 mm long and have 3-5 pairs of leaflets. There is a small cone-shaped structure (i.e. erect conical gland) between the lowest three or four pairs of leaflets. The leaflets (3.5-9 cm long and 15-35 mm wide) are elongated to egg-shaped in outline (i.e. lanceolate to narrowly ovate) with entire margins and pointed tips (i.e. acuminate apices). They have glossy green upper surfaces and paler green undersides.

Flowers and Fruit

The flower clusters (2.5-8 cm long) are borne on stalks (i.e. peduncles) 3-4 cm long and usually contain 4-10 flowers. Individual flowers are borne on stalks (i.e. pedicels) 10-13 mm long that elongate to 25 mm in fruit. Each flower has five yellowish-green, yellowish-brown, or pale yellow sepals (4-10 mm long) and five bright yellow or golden yellow petals (12-16 mm long). The uppermost petal (i.e. standard) is slightly larger than the others and has a notched tip. The flowers also have six or seven stamens, two of which are larger than the others, and three partially-formed stamens (i.e. staminodes). Flowering occurs mainly during spring and autumn.

The cylindrical pods (5-10 cm long and 7-12 mm wide) turn from green to brown or straw-coloured as they mature. They are usually borne in an upright position on stiff stalks. The olive or brown seeds (3.5-5 mm long) are somewhat flattened with smooth or minutely pitted surfaces.

Reproduction and Dispersal

This plant reproduces mainly by seed, which are dispersed by water or in mud sticking to animals, humans, machinery and vehicles. They may also be spread as a contaminant of agricultural produce.

Impacts

Smooth senna (Senna septemtrionalis) is regarded as an environmental weed in Queensland and New South Wales.

Similar Species

Smooth senna (Senna septemtrionalis) is very similar to coffee senna (Senna occidentalis ), sicklepod (Senna obtusifolia ), Java bean (Senna tora ), hairy senna (Senna hirsuta ), Easter cassia ( Senna pendula var. glabrata) and the native arsenic bush (Senna planitiicola). It is also relatively similar to pepper-leaved senna (Senna barclayana). These species can be distinguished by the following differences:

Legislation

Not declared or considered noxious by any state government authorities.

Sources

Anonymous (2006). Germplasm Resources Information Network (GRIN). http://www.ars-grin.gov/cgi-bin/npgs/html/index.pl. National Germplasm Resources Laboratory, National Genetic Resources Program, Agricultural Research Service (ARS), United States Department of Agriculture (USDA), Beltsville, Maryland, USA.

Anonymous (2006). Senna septemtrionalis (Viv.) H. Irwin & Barneby. Arsenic bush. Plants Profile. http://plants.usda.gov/java/profile?symbol=SESE13. National Plant Data Center, National Resources Conservation Service, United States Department of Agriculture, Baton Rouge, Louisiana, USA.

Anonymous (2006). Senna septemtrionalis (Viv.) H.S.Irwin & Barneby, Fabaceae. Pacific Island Ecosystems at Risk (PIER): plant threats to Pacific ecosystems. http://hear.org/pier/species/senna_septemtrionalis.htm. Institute of Pacific Islands Forestry, Hawaii, USA.

Batianoff, G.N. and Butler, D.W. (2002). Assessment of invasive naturalized plants in south-east Queensland. Plant Protection Quarterly 17: 27-34.

Bostock, P.D. and Holland, A.E. (2007). Census of the Queensland Flora 2007. Queensland Herbarium, Environmental Protection Agency (EPA), Brisbane, Queensland.

Green, P. (1994). Flora of Australia, Volume 49, Oceania Islands 1. Australian Biological Resources Study and CSIRO Publishing, Collingwood, Victoria.

Randell, B.R. and Barlow, B.A. (1998). 11. Senna. In: Flora of Australia, Volume 12, Mimosaceae (excl. Acacia), Caesalpiniaceae (ed: P.M. McCarthy). Australian Biological Resources Study and CSIRO Publishing, Collingwood ,Victoria.

Wiecek, B. (2007). Senna septemtrionalis (Viv.) H.S.Irwin & Barneby. New South Wales Flora Online. PlantNET - The Plant Information Network System of Botanic Gardens Trust. http://plantnet.rbgsyd.nsw.gov.au. Royal Botanic Gardens and Domain Trust, Sydney, New South Wales.