Weeds of Australia - Fact Sheet

Top Scientific Name Family Common Names Origin Cultivation Naturalised Distribution Habitat Habit Distinguishing Features Stems and Leaves Flowers and Fruit Reproduction and Dispersal Environmental Impact Legislation Similar Species

Scientific Name

Stylosanthes scabra Vogel

Family

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

Common Names

pencilflower, seca, seca stylo, shrubby stylo

Origin

Native to the Caribbean (i.e. the Bahamas and Cuba) and South America (i.e. Guyana, Venezuela, Brazil, Bolivia, Colombia, Ecuador and Argentina).

Cultivation

Widely cultivated as a pasture legume in the warmer parts of Australia. 'Seca' is the most common and well known of the cultivars that are grown in this country.

Naturalised Distribution

Widely naturalised in northern Australia (i.e. in northern and eastern Queensland, in the northern parts of the Northern Territory, and in northern Western Australia).

Also naturalised overseas in Hawaii.

Habitat

A weed of open woodlands, grasslands, floodplains, levee banks, roadsides, disturbed sites, waste areas and crops in tropical and sub-tropical regions.

Habit

An upright (i.e. erect) woody herbaceous plant or small shrub growing 0.3-2 m tall.

Distinguishing Features

• an upright small woody shrub growing 0.3-2 m tall.
  
  
• its stems are covered with short hairs, some of which are sticky.
  
  
• its compound leaves consist of three leaflets (16-25 mm long and 3.5-9 mm wide).
  
  
• its small pea-shaped flowers are predominantly yellow with reddish centres.
  
  
• its small fruit (8-9.5 mm long) separates into two segments and is topped with a small hooked beak (1.5-2 mm long).

Stems and Leaves

The woody stems are covered with short hairs (i.e. they are pubescent), some of which are often sticky (i.e. glandular). Younger stems vary from pale green to brown or reddish in colour, while older stems are brown or greyish.

The alternately arranged leaves are compound and consist of three leaflets (i.e. they are trifoliate). These leaves each have two toothed leafy structures (i.e. stipules) 15 to 25 mm long at their bases, and are borne on stalks (i.e. petioles) 5-20 mm long. The leaflets are oval (i.e. elliptic), egg-shaped (i.e. ovate) in outline, or somewhat elongated in shape (i.e. oblong-lanceolate) with entire margins and pointed or rounded tips (i.e. acute to obtuse apices). These leaflets (16-25 mm long and 3.5-9 mm wide) are loosely covered in hairs on both surfaces, some of which are sticky (i.e. glandular).

Flowers and Fruit

The small pea-shaped flowers are borne in short and dense spikes in the upper leaf forks. These stalkless (i.e. sessile) flowers are predominantly yellow (occasionally cream or pale yellow) with reddish centres. They have five sepals (4-6 mm long) that are joined together at the base (i.e. into a calyx tube) and five petals (3-6 mm long). The uppermost petal (i.e. standard) is larger than the two side petals (i.e. lateral or wing petals). The two lower petals are joined together and folded (i.e. into the keel). Flowers also have ten small stamens, which are fused to each other, and an ovary topped with a style and stigma.

The small fruit (8-9.5 mm long and 2-2.5 mm wide) is a pod that separates into two segments (i.e. a lomentum). These fruit are hairy (i.e. pubescent) and topped with a small hooked beak (1.5-2 mm long). They contain light brown seeds (up to 2 mm long) that are somewhat kidney-shaped (i.e. reniform).

Reproduction and Dispersal

This species reproduces by seed. These seeds are dispersed by livestock and other animals movement, as a contaminant of hay, and by vehicles and machinery (e.g. slashers and graders).

Environmental Impact

Shrubby stylo (Stylosanthes scabra) is regarded as an environmental weed in Queensland, the Northern Territory and northern Western Australia.

Legislation

Not declared or considered noxious by any state government authorities.

Similar Species

Shrubby stylo (Stylosanthes scabra) is very similar to common stylo (Stylosanthes guianensis), sticky stylo (Stylosanthes viscosa), Caribbean stylo (Stylosanthes hamata) and Townsville stylo (Stylosanthes humilis). These species can be distinguished by the following differences:

• Shrubby stylo (Stylosanthes scabra) is a relatively upright (i.e. erect) shrubby plant growing 0.3-2 m tall. Its stems are densely covered in soft hairs, some of which are sticky (i.e. glandular). Its small fruit are somewhat hairy (i.e. pubescent) and are topped with a short hook (1.5-2 mm long).
  
  
• common stylo (Stylosanthes guianensis) is a relatively upright (i.e. erect) shrubby plant growing 0.5-1.5 m tall. Its stems are covered in short soft hairs as well as stiff yellow or reddish bristly hairs. Its small fruit are hairless (i.e. glabrous) and are topped with a very inconspicuous hook (less than 1 mm long).
  
  
• sticky stylo (Stylosanthes viscosa) is a low-growing to relatively upright (i.e. erect) plant growing up to 0.8 m tall. Its stems are densely covered in sticky (i.e. glandular) hairs. Its small fruit are are hairless (i.e. glabrous) and are topped with a very inconspicuous hook (less than 1 mm long).
  
  
• Caribbean stylo (Stylosanthes hamata) is a low-growing (i.e. prostrate or decumbent) plant growing up to 0.5 m tall. Its stems are partially covered in small soft hairs. Its small fruit are sparsely hairy (i.e. sparsely pubescent) and are topped with a long hook (about 4 mm long).
   
• Townsville stylo (Stylosanthes humilis) is a low-growing (i.e. prostrate or decumbent) plant growing up to 0.4 m tall. Its stems are partially covered in tiny soft hairs, but may appear almost hairless. Its small fruit are sparsely hairy (i.e. sparsely pubescent) and are topped with a very long hook (4-6 mm long).