red-head cotton bush

Asclepias curassavica
habit (Photo: Sheldon Navie)
broken stem exuding its milky sap (Photo: Sheldon Navie)
elongated leaves (Photo: Sheldon Navie)
close-up of leaf underside (Photo: Sheldon Navie)
younger leaves and flower buds (Photo: Sheldon Navie)
flower clusters (Photo: Sheldon Navie)
close-up of flowers (Photo: Sheldon Navie)
immature fruit (Photo: Sheldon Navie)
mature fruit releasing their seeds (Photo: Sheldon Navie)
Herb
Opposite
Simple
Yellow
Green
Discoloured

A long-lived herbaceous plant or small shrub growing up to 1.5 m tall. Its stems and leaves contain a milky white sap. Its paired leaves (5.5-15 cm long) are narrow with pointed tips. Its star-shaped flowers are red or orange with a yellow crown -like structure at the centre. Its paired fruit (5-6 cm long and 8-12 mm wide) contain numerous brown seeds topped with a tuft of long cottony hairs.

Common names 
Also known as: red-head cotton bush, annual milkweed, blood flower, bloodflower, false ipecac, milkweed, red head cottonbush,
Family 
Apocynaceae
Deciduous 
No
Flowering time 
Summer-Winter
Native/Exotic 
Exotic
Origin 
The exact origin of this species is obscure, but it is native to the tropical and sub-tropical regions of the America's.
Notifiable 
No
Council declaration 
Class R – Reduce populations
Known distribution 

Widely naturalised in Australia, but most common and widespread in the eastern parts of the country (i.e. in eastern Queensland and the coastal districts of northern New South Wales).

Habitat 

A common weed of disturbed sites, waste areas, roadsides, railways, wetlands, swamps, creek banks, river beds, riparian vegetation, floodplains, coastal sites, old cultivation and neglected pastures.

Habit 

An upright (i.e. erect) and long-lived (i.e. perennial) herbaceous plant or small shrub that usually grows 0.3-1.2 m tall, but may occasionally reach up to 1.5 m in height.

Impact and control methods 

Red-head cotton bush (Asclepias curassavica) is regarded as an environmental weed in south-eastern Queensland, and was recently ranked among the 200 most invasive plants in the region. It is a common weed of open woodlands, grasslands, pastures, disturbed sites, waste areas and roadsides, but is mainly a concern in riparian areas and wetlands in this region.

Stem and leaves 

"The smooth, rounded, stems may become slightly woody at the base as they mature. They are dull green or suffused with dull red and contain a milky sap (i.e. latex). Younger stems are finely hairy (i.e. puberulent), while older stems are hairless (i.e. glabrous).

The oppositely arranged leaves are borne on stalks (i.e. petioles) 5-20 mm long and have paler undersides. They vary from narrowly oval (i.e. narrowly-elliptic) to elongated (i.e. lanceolate) in shape with a pointed tip (i.e. acute or acuminate apex) and a gradually narrowing (i.e. attenuate) base. These leaves (5.5-15 cm long and 6-30 mm wide) have entire margins and are mostly hairless (i.e. glabrous), though both surfaces may have some scattered hairs when the leaves are young."

Flowers and fruits 

"The flowers are arranged in clusters in the upper leaf forks or at the tips of the branches (i.e. in terminal or axillary umbels). Each of these clusters is borne on a stalk (i.e. peduncle) 2-5.5 cm long and has 6-15 flowers. The individual flowers are borne on smaller stalks (i.e. pedicels) 1-2.5 cm long that all originate from the same point. They have five brick red to scarlet petals (5-8.5 mm long) that are fused together at the base and bent backwards (i.e. reflexed). At the centre of each flower is a yellow or orange crown-shaped structure (i.e. corona) 8-11 mm across. The flowers also have five small narrow green sepals (2-4 mm long), five yellow stamens, and an ovary topped with two styles that are fused together at the tip and expanded into a five-sided stylehead. Flowering occurs from spring through to autumn.

The large fruit (i.e. follicles) are narrowly egg-shaped (i.e. ovoid) or spindle-shaped (i.e. fusiform) and taper to a beak at the tip. These fruit (5-6 cm long and 8-12 mm wide) are borne in pairs and turn from green to pale brown in colour as they mature. They are smooth and hairless (i.e. glabrous) and are held upright (i.e. erect or ascending). When fully mature they split lengthwise to release numerous brown seeds. These seeds (4-6 mm long and 2.2-4 mm wide) are egg-shaped in outline (i.e. ovate), flattened, and topped with a tuft of cottony hairs (i.e. coma) 2-3 cm long. Fruiting occurs from late summer through to winter."

Reproduction and dispersal 

This species reproduces only by seed. These seeds are mostly dispersed by wind and water.