Castor oil plant is a medium to tall shrub with large star-like leaves. It is poisonous to humans, dogs and livestock.
Castor oil plant:
Castor oil plant contains a toxin called ricin. It is toxic to humans, capable of causing serious illness and death. Flowers, leaves and especially the seeds are poisonous. Eating castor oil plant causes:
Temporary blindness may occur if the sap gets into the eyes. Touching leaves and seeds can cause dermatitis in people with sensitive skin.
Castor oil plant is poisonous to dogs and livestock including cattle, horses, pigs, sheep and poultry. Livestock rarely eat this weed due to the odour of the leaves. However, poisoning can occur if grain is contaminated with seeds. Symptoms are similar to human poisoning. It may take a few hours or days for symptoms to appear.
Honey bees have been poisoned by castor oil plants.
Castor oil plant is a fast-growing shrub usually 3 m tall (occasionally up to 12 m). It is a perennial plant unless it is growing in areas with regular severe frosts where it will die in winter.
There is a lot of variation in this plant. The flowers or leaves on one plant may be a different colour to other plants, even when growing in the same area.
Castor oil plant has a strong tap root and thick fibrous side roots.
Castor oil plants looks similar to two other weed species:
Both of these plants have leaves with 3-5 lobes and flowers with petals.
Castor oil plant is common along the coastal regions of NSW but it is also found in scattered populations throughout NSW.
It is native to Africa and Eurasia.
Castor oil plant grows in warm temperate and sub-tropical climates in a wide variety of soils. It is drought tolerant but grows best in soils with high moisture. It is not frost tolerant. It grows:
When the fruit pods dry out the seed shoots out, sometimes landing many metres away. Seeds germinate in autumn to spring or can stay viable for at least four years. Seeds are spread:
Parsons, W.T. and Cuthbertson, E.C. (2001). Noxious weeds in Australia 2nd Edn, CSIRO Publishing, Collingwood.
PlantNET (The NSW Plant Information Network System). Royal Botanic Gardens and Domain Trust, Sydney. Retrieved 2020 from: https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Ricinus~communis
Sasidharan, R. & Venkatesan, R. (2019). Seed elaiosome mediates dispersal by ants and impacts germination in Ricinus communis. Frontiers in Ecology and Evolution, 7, 246.
Be careful when controlling this plant as it is poisonous. Wear protective clothing including gloves and eye protection before starting control work.
Castor oil plant can be controlled by:
The key is to follow up any control work to treat plants that have re-grown or stop new plants from growing and seeding. Check sites for at least four years.
Large areas of castor oil plant can be slashed or mown, followed by cultivation. Keep cultivation shallow to stop seeds from being buried deeply. Deeper burial can cause dormancy in seeds and this could make control difficult in future. Check the area and control any regrowth or new seedlings.
Young plants can be hand pulled or dug out quite easily. Larger plants can be removed if the soil is damp. It is important to remove as much of the roots as possible to stop the plant from re-growing. Contact your local council for advice on disposal.
If possible spray before plants set seed. If plants have fruit, collect and dispose of the fruit. If there are too many to collect follow up control of seedlings will be needed. Check controlled areas within one month of treatment.
This method is best before plants get too tall and when there is no risk of spraying desirable plants nearby. Cover all foliage with herbicide.
Cut trunks or stems and apply herbicide within 15 seconds.
See Using herbicides for more information.
PERMIT 9907 Expires 31/03/2025
Glyphosate 360 g/L
(Various products)
Rate: 1 part glyphosate to 50 parts water
Comments: Spray seedlings and coppice shoots.
Withholding period: Nil.
Herbicide group: 9 (previously group M), Inhibition of 5-enolpyruvyl shikimate-3 phosphate synthase (EPSP inhibition)
Resistance risk: Moderate
PERMIT 9907 Expires 31/03/2025
Glyphosate 360 g/L
(Various products)
Rate: 1 part glyphosate to 1.5 parts water
Comments: Cut stump/scrape stem application for saplings. Stem injection application large trees and shrubs.
Withholding period: Nil.
Herbicide group: 9 (previously group M), Inhibition of 5-enolpyruvyl shikimate-3 phosphate synthase (EPSP inhibition)
Resistance risk: Moderate
2,4-D amine 625 g/L
(Various products)
Rate: 340 mL per 150 L of water, or 3.4 L/Ha
Comments: Apply to young, actively growing plants.
Withholding period: 7 days withholding for grazing
Herbicide group: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: Moderate
Picloram 44.7 g/L + Aminopyralid 4.47 g/L
(Vigilant II ®)
Rate: Undiluted
Comments: Cut the stump close to the ground (no higher than 10 cm). Apply a 3–5 mm layer of gel for stems less than 20 mm. Apply 5 mm layer on stems above 20 mm.
Withholding period: Nil.
Herbicide group: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: Moderate
Triclopyr 600 g/L
(Garlon® 600)
Rate: 1.0 L per 60 L of diesel
Comments: Basal bark application for plants up to 5 cm basal diameter. Cut stump application for plants with larger basal diameter.
Withholding period: Nil.
Herbicide group: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: Moderate
The content provided here is for information purposes only and is taken from the Biosecurity Act 2015 and its subordinate legislation, and the Regional Strategic Weed Management Plans (published by each Local Land Services region in NSW). It describes the state and regional priorities for weeds in New South Wales, Australia.
Area | Duty |
---|---|
All of NSW | General Biosecurity Duty All pest plants are regulated with a general biosecurity duty to prevent, eliminate or minimise any biosecurity risk they may pose. Any person who deals with any plant, who knows (or ought to know) of any biosecurity risk, has a duty to ensure the risk is prevented, eliminated or minimised, so far as is reasonably practicable. |
Murray |
Regional Recommended Measure* (for Regional Priority - Eradication)
Land managers should mitigate the risk of the plant being introduced to their land. Land managers should eradicate the plant from the land and keep the land free of the plant. A person should not deal with the plant, where dealings include but are not limited to buying, selling, growing, moving, carrying or releasing the plant. Notify local control authority if found. |
*To see the Regional Strategic Weeds Management Plans containing demonstrated outcomes that fulfil the general biosecurity duty for this weed click here |
Reviewed 2023