Spiny emex (Rumex hypogaeus)

Also known as: cathead, doublegee, prickly jacks, three-cornered jacks

Spiny emex is a low growing herb with spiny woody fruit. It is a weed in crops and pastures and can poison grazing animals, especially sheep.

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How does this weed affect you?

Spiny emex:

reduces crop yields, particularly cereals
contaminates crops, especially dried fruit
competes with pastures, reducing productivity
competes with native plants in semi-arid areas
can be poisonous to grazing animals, especially sheep that eat large quantities
has hard spiny fruits that can injure people and animals.

Livestock poisoning and health

Spiny emex leaves contain oxalates which are toxic to ruminants, especially sheep. The spiny fruit can injure feet and cause lameness.

What does it look like?

Spiny emex is a low-growing annual herb up to 40 cm high. The leaves form a rosette when the plant is young.

Leaves are:

3–9 cm long and 1.5–7 cm wide
triangular to oval shaped
sometimes toothed along the edges with minute rounded teeth
on stalks 2–10 cm long surrounded by a sheath.

Flowers are:

green and not obvious
male or female, the femal flowers have sharp spines
present year round.

Fruit are:

hard and woody with one seed
green ripening to brown
up to 13 mm wide
triangular with three sharp spines.

Seeds are:

brown and glossy
rarely shed from the fruit.
up to 80 cm long.

Stems are:

purplish at the base and nodes
fleshy and hairless
ribbed
mostly spread across the ground rather than upright.

Roots are:

a deep taproot
fleshy.

Similar looking plants

Spiny emex looks similar to lesser Jack (Rumex spinosus), which is more erect and has smaller fruit (4–6 mm wide) with shorter spines (1–2 mm long).

Scientific name change

This plant was previously named Emex australis.

Where is it found?

Spiny emex has been recorded growing in all regions of NSW except the Central Tablelands and the South East.

It is native to South Africa.

What type of environment does it grow in?

Spiny emex grows in a range of climates including subtropical, temperate and semiarid. It tolerates a wide range of soil types. Plants have been found growing:

amongst crops and in orchards,
in pastures
in disturbed areas such as roadsides and tracks
in riparian areas including the edges of creeks, rivers and lakes, also claypans
in natural areas, especially in semi-arid areas.

How does it spread?

Spiny emex plants can produce up more than 1100 seeds. The seeds can live in the soil for more than 4 years and the seedbank may contain more than 5000 seeds per square metre.

Seeds are spread:

mostly by fodder, especially lucerne hay and feed wheat
in other contaminated produce such as clover seed
by spines on the fruit attaching to shoes and animal feet
by attaching to tyres including light aircraft tyres
in flood water

References

Gilbey, D.J., Weiss, P.W. and Shepherd, R.C.H. (1998). Emex australis Steinh. In: F.D. Panetta, R.H. Groves and R.C.H. Shepherd (eds), The Biology of Australian Weeds, Volume 2. R.G. & F.J. Richardson, Melbourne.

Keighery, G. (1996). Emex australis in Western Australia; an amenity or conservation problem? Plant Protection Quarterly 11(4): 143-144.

Parsons, W.T. and Cuthbertson, E.G. (2001). Noxious Weeds of Australia. CSIRO Publishing, Victoria.

PlantNET (The NSW Plant Information Network System). Royal Botanic Gardens and Domain Trust, Sydney. Retrieved 10 January 2025 from: https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Rumex~hypogaeus

More information

Control

Successful weed control relies on follow up after the initial efforts. This means looking for and killing regrowth or new seedlings. Using a combination of control methods is usually more successful. Check for and control new plants for several years.

Prevention

Source fodder, especially lucerne hay, from areas that are not infested with spiny emex. A fodder declaration form may be requested.

Physical removal

By hand

Small infestations and isolated plants can be dug out. Dispose of plants with seeds by burning them.

By machine

Prickle rollers are used to gather and remove surface spiny emex fruit from drying greens in vineyards.

Cultivation

Cultivation kills seedlings. It can assist control of older plants when combined with chemical control. Avoid deep ploughing because seeds will be buried and become dormant, with the potential to resprout if they are brought up closer to the surface.

Chemical control

Spot spraying

Spray actively growing plants. Ensure that all of the foliage is covered with the herbicide mix.

Boom spraying

Treat when plants are young and actively growing.

Herbicide options

WARNING - ALWAYS READ THE LABEL
Users of agricultural or veterinary chemical products must always read the label and any permit, before using the product, and strictly comply with the directions on the label and the conditions of any permit. Users are not absolved from compliance with the directions on the label or the conditions of the permit by reason of any statement made or not made in this information. To view permits or product labels go to the Australian Pesticides and Veterinary Medicines Authority website www.apvma.gov.au

See Using herbicides for more information.

2,4-D 300 g/L + Picloram 75 g/L (Tordon® 75-D)
Rate: 300 mL per 100 L of water
Comments: Spot spray. For use in grass pastures.
Withholding period: Do not graze or cut crops (except sugar cane 8 weeks) or pastures for stock food for 7 days after application.
Herbicide group: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: Moderate

Glyphosate 360 g/L (Various products)
Rate: 500–700 mL per 100 L of water
Comments: Spot spray.
Withholding period: Nil.
Herbicide group: 9 (previously group M), Inhibition of 5-enolpyruvyl shikimate-3 phosphate synthase (EPSP inhibition)
Resistance risk: Moderate

Glyphosate 360 g/L (Various products)
Rate: 2.0–3.0 L/ha
Comments: Boom spray. Young, actively growing plants.
Withholding period: Nil.
Herbicide group: 9 (previously group M), Inhibition of 5-enolpyruvyl shikimate-3 phosphate synthase (EPSP inhibition)
Resistance risk: Moderate

Biosecurity duty

The content provided here is for information purposes only and is taken from the NSW 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.

For technical advice and assistance with identification please contact your local council weeds officer.

Reviewed 2025