NSW WeedWise

Horehound (Marrubium vulgare)

Also known as: white horehound
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Horehound is a small shrub with wrinkled leaves. It outcompetes pasture species and contaminates wool.

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Control

Biosecurity duty

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How does this weed affect you?

Horehound:

  • outcompetes pasture plants, reducing productivity
  • is unpalatable to livestock and taints meat if livestock eat it when feed is scarce
  • has burrs that devalue wool
  • occasionally invades cropping land
  • invades disturbed native vegetation areas.

What does it look like?

Horehound is an upright perennial shrub up to 75 cm tall.

Leaves are:

  • 1–3.5 cm long and up to 3 cm wide
  • circular or sometimes slightly diamond shaped
  • wrinkled with irregular rounded teeth along the edges
  • hairy above and very hairy on the underside
  • on stalks up to 2 cm long
  • opposite along the stems.

Flowers are:

  • white with fused petals and surrounded by a green tube
  • in dense clusters of more than 12 flowers at the base of leaves
  • 6–12 mm long
  • present throughout the year.

 Fruit:

  • are a brown burr with 10 hooked spines
  • have up to 4 seeds.

Seeds are:

  • black or brown
  • 1–2 mm long
  • egg shaped
  • slightly rough on the surface.

Stems are

  • woody at the base
  • square in cross section
  • covered with grey to white dense hairs.

Where is it found?

Horehound is scattered across much of NSW but is not common on the North Coast, Hunter or far northwest of the Western Region. 

It is native to southern and western Europe, central and western Asia and north Africa. Horehound was first recorded as naturalised in Australia in the 1840s.

What type of environment does it grow in?

Horehound can grow in semi-arid, temperate and subtropical climates. Plants are drought and frost tolerant, but they do not tolerate waterlogged soils or survive fire. Horehound grows best on well drained, alkaline soils and tolerates infertile soils. 

Plants grow best in full sun. Roadsides, fence lines, stock camps and other vacant neglected land are common areas where horehound grows.  Horehound can invade disturbed sites in natural bushland including red gum, dry coastal vegetation, mallee shrubland, lowland and open grasslands, grassy woodland and rocky outcrops.

How does it spread?

By seed

A mature horehound plant can produce up to 20,000 seeds per year. The seeds can survive in the soil for 7-10 years. Horehound seeds spread:

  • by attaching to wool, fur and feathers
  • by attaching to clothing, tyres and vehicles
  • in moving water
  • as a contaminant of fodder
  • in horse manure.

References

Harvey, K.J., McConnachie, A.J. Sullivan, P. Holtkamp, R. & Officer, D. (2021). Biological control of weeds: a practitioner's guide for south east Australia. New South Wales Department of Primary Industries, Orange.

Identic Pty Ltd. and Lucid central (2016). Environmental Weeds of Australia Fact sheet: Marrubium vulgare L. Retrieved 02 May 2025 from: https://keyserver.lucidcentral.org/weeds/data/media/Html/marrubium_vulgare.htm

Papay, I. (2013). Marrubium vulgare (horehound). CABI Compendium Datasheet In: Invasive Species Compendium. Retrieved 02 May 2025 from: https://www.cabidigitallibrary.org/doi/full/10.1079/cabicompendium.119607

Parsons, W.T., & Cuthbertson, E. G. (2001). Noxious weeds of Australia. 2nd edition. CSIRO publishing.

PlantNET (The NSW Plant Information Network System). Royal Botanic Gardens and Domain Trust, Sydney. Retrieved 02 May 2025 from: https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Marrubium~vulgare

Weiss, J., Ainsworth, N., Faithfull, I & Turnbull, K. (2000). Best Practice Management Guide for Environmental Weeds: Horehound, Marrubium vulgare. Cooperative Research Centre for Weed Management Systems.

More information

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Control

Pasture management

If possible, maintain dense, healthy pastures to reduce horehound infestations.

Fire

Fire kills mature plants and can reduce the seed bank by up to 80%[BV1] . Burning reduces the bulk of large infestations. Follow up is required to treat seedlings.

Physical removal

By Hand

Small plants can be dug out by hand. The plants can be disposed of by burning.

Machinery

Deep cultivation can control plants, especially in hot dry weather when the disturbed plants will dry out and die. Seedlings appearing after fire, can be killed by ploughing.

Biological control

Two moths have been released, and both moths significantly impact horehound helping with its control.

  • The horehound plume moth (Wheeleria spilodactylus) is widespread and does not need redistribution. However the moths can be moved from site to site to assist control programs.
  • Horehound clear wing moth (Chamaesphecia mysiniformis) may need to be introduced to an infestation or area. This may be labour intensive; however it has resulted in good control of the weed. 

Contact your local council weeds officer for information about using biological control agents.

Chemical control

Spot spraying

Spray actively growing plants. Cover all of the foliage with herbicide.

Boom spraying

Time of spraying varies between herbicides, check the label for details.

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 LV ester 680g/L (Estercide® Xtra)
Rate: 1.7 to 3.3 L/ha
Comments: Boom spray application for seedlings in pastures without legumes, from late autumn to early spring
Withholding period: Do not graze or cut for stock food for 7 days after application.
Herbicide group: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: Moderate

Aminocyclopyrachlor 240 g/L (Method® 240 SL)
Rate: 200-500 mL per 100 L of water
Comments: Spot spray with a handgun, hand-held sprayer or backpack sprayer. Thoroughly and uniformly wet the foliage but avoid spraying to the point of run off.
Withholding period: Nil for domestic grazing. See label for livestock export conditions.
Herbicide group: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: Moderate

Dicamba 750 g/L (Kamba® 750)
Rate: 53 mL per 100 L of water. Add a surfactant.
Comments: Spray prior to flowering. For non crop situations.
Withholding period: Do not harvest, graze or cut for stock food for 7 days after application.
Herbicide group: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: Moderate

Dicamba 750 g/L (Kamba® 750)
Rate: 800 mL/ha Use a minimum of 1500 L of solution per ha. Add a surfactant.
Comments: Boom spray for non-crop situations. Spray prior to flowering.
Withholding period: Do not harvest, graze or cut for stock food for 7 days after application.
Herbicide group: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: Moderate

MCPA 500 g/L (Various products)
Rate: 3 L per hectare
Comments: Boom spray application. Apply in Autumn when plants are at the seedling stage.
Withholding period: Do not graze or cut for stock food for 7 days after application.
Herbicide group: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: Moderate

Picloram 100 g/L + Triclopyr 300 g/L + Aminopyralid 8 g/L (Grazon® Extra)
Rate: 350 mL in 100 L of water
Comments: Apply as foliar spray pre-flowering
Withholding period: Where product is used to control woody weeds in pastures there is a restriction of 12 weeks for use of treated pastures for making hay and silage; using hay or other plant material for compost, mulch or mushroom substrate; or using animal waste from animals grazing on treated pastures for compost, mulching, or spreading on pasture/crops.
Herbicide group: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: Moderate

Triclopyr 300 g/L + Picloram 100 g/L (Various products)
Rate: 350 mL in 100 L of water
Comments: Apply as a foliar spray pre-flowering.
Withholding period: Nil.
Herbicide group: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: Moderate

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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.

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

Reviewed 2025

www.dpi.nsw.gov.au