Type of weed: Woody weed
Flower colour(s): Red
Priority Weed Local Priority Weed. (See more weeds of the Local Priority Weed class.)
Flowering Months: January, February
Spreading shrub to about 6 m tall. Perennial in moist areas, annual in frosty areas. Has hollow stems; roots are thick and fibrous.
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.
There are native nurseries in several Blue Mountains villages, including Glenbrook, Lawson and Katoomba. Please also ask at your favourite local nursery.
- Hand remove
- Cut and paint
Grasp stem at ground level. Rock weed backwards and forwards to loosen roots, then pull out gently. Carefully tap the roots to dislodge attached soil. Replace disturbed soil and pat down.
- Leave weeds so that roots do not make contact with soil; on a rock, for instance. A small amount of debris may be hung in a tree or removed from the site.
- Vary the position of your body to avoid fatigue when removing plants by hand over extended periods.
Note: Herbicides that may be used for this weed include Glyphosate.
Please consult the Herbicide page of this website to help you decide whether to spray, how to do it safely and more.
Cut and paint
Useful for small to medium sized woody weeds up to 10 cm in diameter.
Make a horizontal cut as close to the ground as possible with secateurs or loppers, and immediately apply concentrated Glyphosate to the exposed stump surface. Do not allow the surface to get covered with soil.
Specific control tips for this weed
- 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.
For key points on these techniques:
Local Priority Weed
- The plant should be fully and continuously suppressed and destroyed.
- Plants under 4 metres in height should be fully and continuously suppressed and destroyed.
- The spread of this plant should be adequately contained to prevent spread impacting on priority assets. Weed notices will only be issued for these weeds under special circumstances.