Type of weed: Woody weed
It is a spreading shrub to about 6 m tall. It is perennial in moist areas, annual in frosty areas. It has hollow stems; roots are thick and fibrous.
It is distinguished by large (50 cm) divided leaves with an objectionable smell when crushed.
Flowers are in terminal clusters or at the leaf-stem junction. Upper flowers are female, reddish; lower flowers male. It flowers in late summer.
Fruit at first is a soft, spiny, green capsule that dries to reddish-brown; each capsule is about 2 cm long. Seeds are smooth, patterned black and fawn and to 1.7 cm long.
Note: Castor Oil plant is toxic to stock and humans, especially the seeds.
The capsules disperse seed through explosion.
Impact on bushland
Castor Oil Plant grows wherever there is disturbance. If left untreated, Castor Oil Plant will grow to form dense stands along river banks and can grow to large sizes, outcompeting with native plants.
- Christmas Bush (Ceratopetalum gummiferum)
- Native Peach (Trema aspera)
- Red Bottlebrush (Callistemon citrinus)
- Bleeding Heart (Omolanthus populifolius).
Council provides a tool, on its Mountain Landscapes website, to help you choose native alternative plantings. Choose your village, soil, vegetation community and the purpose of your planting, and the tool will give you suggestions.
- Hand pull seedlings if all the roots can be removed. Dense seedling beds can be sprayed with herbicide. Use a selective herbicide to prevent killing native grasses (this will assist to prevent erosion on creek and river banks).
- Cut and paint with herbicide more established plants.