Calotropis

Calotropis is a shrub or small tree commonly found along roadsides, waterways, and other disturbed areas throughout the Kimberley and Pilbara regions. It is easily recognised by its large grey-green leaves and dense clusters of purple and white flowers, which develop into large seed pods containing numerous black seeds, each attached to a silky tuft that aids dispersal. A major weed of pastoral lands in Queensland and the Northern Territory, Calotropis also poses a significant threat to conservation areas, where dense infestations can obstruct waterways, restrict access, and displace native vegetation.

• Flowers are produced in clusters of 3 to 15 in the forks of the upper leaves.
• Each cluster is borne on a stalk 20 to 55 mm long, with individual flowers on stalks 15 to 25 mm long.
• Flowers are trumpet shaped, 15 to 25 mm across, with five spreading petals.
• Petals are white or pinkish with dark purple or purplish brown tips and a purple crown shaped centre.
   

• Fruits are large, rounded to egg shaped pods, 6 to 12 cm long and 3 to 7 cm wide.
• Pods are greyish green with thick, spongy skins that split open when mature.
• Each fruit contains numerous flattened brown seeds.
• Seeds have a tuft of long, white, silky hairs (35–50 mm long) that aid dispersal.
   

Calotropis is similar to Calotropis gigantea, which is also present in the Kimberley region of WA.  Calotropis differs from C. gigantea by having more cylindrical shaped flower buds, a larger corolla (2.5–3.5 cm) with lobes that are usually curved backward, and long ovate or oblong and shorter sepals. C. gigantea doesnt readily set seed. From a management perspective, they can be treated the same.

Although most of the seeds are dropped near parent plants, seeds can also travel further by wind facilitated by the silky pappus or floating along watercourses.

• Produces a milky sap that is toxic to humans and toxic livestock.  The latex is quite bitter, therefore its rarely eaten.
• Forms dense thickets on alluvial floodplains and spreads into adjacent over‑grazed pastures.
• Thrives on poor soils, particularly where overgrazing has removed competition from native grasses.
• Dense infestations outcompete native plants and alter the structure and appearance of grassland plant communities.
• Ugly blight on the landscape