Mouse-ear hawkweed (Pilosella officinarum)

PROHIBITED MATTER: If you see this plant report it. Call the NSW Biosecurity Helpline 1800 680 244

Mouse ear hawkweed is a small herb that has yellow daisy-like flowers. It invades native vegetation in alpine regions and can invade pastures, reducing productivity.

This weed belongs to the group Hawkweeds - Pilosellas

This plant must not be sold anywhere in NSW

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How does this weed affect you?

Mouse-ear hawkweed forms dense mats with thousands of plants per square metre. They

outcompete native plants in native grasslands
reduce food and habitat for native animals
compete with pastures and reduce grazing productivity
invade gardens and roadsides
increase soil acidity.

Mouse-ear hawkweed is a threat to biodiversity in alpine regions in Australia.

What does it look like?

Mouse-ear hawkweed is a perennial herb that grows up to 30 cm tall, though usually 10 - 20 cm tall. It is highly variable in appearance. Milky sap is released when the stems or leaves are broken. Plants may have stolons or rhizomes. The following description is for the subspecies found in NSW, Pilosella officinarum subsp. officinarum.

Leaves are:

at the base of the plant in a rosette
also grow along stolons
dull green on top and whitish underneath
egg-shaped and narrow at the base
3–10 cm long and 1.5–2.0 cm wide
smooth or slightly toothed on the edges
hairy
stalkless.

Flowers are:

pale yellow, sometimes with a red or purplish stripe on the outside of the lower petals
daisy-like with square ended petals
1–2 cm in diameter
solitary on unbranched stems
present mostly in spring and summer.

Seeds are:

dark brown to black
cylindrical and tapered
ribbed
2 mm long with a short whitish pappus

Flower stems are:

up to 30 cm long
covered in short, stiff hairs.

Stolons are:

hairy stems growing horizontally above the ground
up to 30 cm long
form roots at the nodes.

Roots are:

slender

Similar looking plants

Mouse-ear hawkweed looks similar to these introduced plants:

Wall hawkweed (Hieracium murorum), which is much taller and the leaves have stalks.
King devil hawkweed (Pilosella piloselloides), which is also much taller and has multiple flowers on branched stems.
Dandelions (Taraxacum officinale), which have leaves that are often deeply lobed. They do not have stolons.
Flatweed, also called catsear (Hypochaeris species), which have deeply toothed or lobed leaves. They do not have stolons.

Mouse-ear hawkweed also looks like the native plant felted buttercup (Ranunculus muelleri) when young. Its leaves only grow to 3 cm long and are not silverish or whitish on the underside . The flowers are up to 3.5 cm in diameter and only have 5 petals.

Where is it found?

Mouse ear hawkweed is native to northern and central Europe.

The first naturalised plants were found in 2014 in Kosciusko National Park. Bushwalkers may have accidently introduced carried the seeds onto the site.

What type of environment does it grow in?

Mouse-ear hawkweed is frost tolerant and can grow on a wide range of soil types. It prefers cool climates with an annual rainfall above 500 mm. It has been found growing in grasslands, eucalyptus woodlands with grassy understorey and in pastures. Plants are often found in areas where the soil has been disturbed.

Maps and records

Recorded presence of Mouse-ear hawkweed during property inspections (Map: Biosecurity Information System - Weeds, 2017-2026)
These records are made by authorised officers during property inspections under the Biosecurity Act 2015. Officers record the presence of priority weeds in their council area and provide this to the NSW Department of Primary Industries. Records reflect the presence of the weed on the date of inspection.

How does it spread?

By seed

Hawkweed plants can mature in approximately 5 months. Infestations can produce up to 40,000 seeds per square metre. Some seeds may remain viable in the soil for up to 5 years. The seeds have tufts that help the seed attach to hair, fur, and vehicles. Seeds can be spread by:

wind and water
sticking to boots, clothing and camping or other recreational equipment
attaching to animals
sticking to vehicles, ski machinery or slashers
movement of contaminated seed.

By plant parts

Plants form dense mats via rhizomes and stolons that spread out from a parent plant. New plants can grow from root fragments.

References

Hamilton, M.A. Cherry, H. Turner, P.J. (2015)\. Hawkweed eradication from NSW: Could this be ‘the first’?. Plant Protection Quarterly Vol.30(3): 110-115

Healy, A. J. (1962). Dandelions and related rosette weeds in New Zealand. In Proceedings of the New Zealand Weed Control Conference (Vol. 15, pp. 53-85).

James, T., Popay, I. Champion, P., Grbavac, N. & Rhode, B. (2012) An Illustrated guide to weed seeds of New Zealand. NZ Plant protection Society.

PlantNET (The NSW Plant Information Network System). Royal Botanic Gardens and Domain Trust, Sydney. Retrieved 23 September 2022 from: https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=in&name=Pilosella~officinarum

Williams, N.S.G. and Holland, K.D. (2007). The ecology and invasion history of hawkweeds (Hieracium species) in Australia, Plant Protection Quarterly, 22(2): 76-80

Wilson, L. M. (2006).Key to Identification of Invasive and Native Hawkweeds (Hieracium Supp.) in the Pacific Northwest. British Columbia, Ministry of Forests and Range, Forest Practices Branch, Invasive Alien Plant Program.

More information

Control

Please do not attempt to treat or dispose of this weed yourself. Report this plant if you see it anywhere in NSW by calling the helpline listed at the top of this page immediately.

NSW DPIRD, Agriculture and Biosecurity will lead an initial response for the treatment and disposal of the plant to stop it from spreading.

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.

PERMIT 95047 Expires 31/07/2026
Picloram 20 g/kg (Tordon® Granules)
Rate: 45 g/m2
Comments: Apply as a spot application by hand or hand spreader. Do not apply more than 1 application per year. See permit for further critical comments.
Withholding period: Nil.
Herbicide group: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: Moderate

PERMIT 14249 Expires 31/03/2030
Picloram 100 g/L + Triclopyr 300 g/L + Aminopyralid 8 g/L (Grazon® Extra)
Rate: 250-500 mL per 100 L
Comments: Spray plants from October to May. Adding a surfactant, BS 1000 or equivalent at 100 mL per 100 L will improve uptake. See permit for further critical comments.
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

PERMIT 14249 Expires 31/03/2030
Triclopyr 300 g/L + Picloram 100 g/L (Various products)
Rate: 250-500 mL per 100 L
Comments: Spray plants from October to May. Adding a surfactant, BS 1000 or equivalent at 100 mL per 100 L will improve uptake. See permit for further critical comments.
Withholding period: Nil.
Herbicide group: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: Moderate

PERMIT 14558 Expires 30/11/2029
Clopyralid 300 g/L (Lontrel®)
Rate: 5 mL in 1 L of water
Comments: Spot spray application only for National Parks and non-agricultural adjoining lands. Only for use by NPWS employees and contractors, See permit for further critical comments.
Withholding period: 1-12 weeks (see label).
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: Use leaf wiping application technique. Apply to at least 50% of the leaves of the rosette plant by wiping the applicator along the middle of each leaf. For use in non-crop areas, including native vegetation, conservation areas, gullies, reserves and parks.
Withholding period: Nil.
Herbicide group: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
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.
All of NSW	Prohibited Matter A person who deals with prohibited matter or a carrier of prohibited matter is guilty of an offence. A person who becomes aware of or suspects the presence of prohibited matter must immediately notify the Department of Primary Industries *All species in the genus Pilosella* are Prohibited Matter**

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

Reviewed 2026