Mintweed (Salvia reflexa)

Also known as: blue salvia

Mintweed is a small grey-green plant with square stems and pale blue tubular flowers. It is toxic to livestock.

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How does this weed affect you?

Mintweed is mostly a weed in summer crops and pastures. It:

is toxic to livestock.
competes with pastures, reducing productivity
competes with and reduces the yields of cereal crops.

Livestock poisoning

Very high levels of nitrates in mintweed can kill livestock, including cattle and sheep. Mintweed is rarely eaten by livestock as it has a strong odour. However, in autumn, when the plant dies off, it loses the strong odour and livestock may eat it. Livestock have also died from eating contaminated hay.

What does it look like?

Mintweed is a branched, upright, summer-growing annual herb up to 60 cm tall. It has a strong mint odour when crushed.

Leaves are:

bluish green
1.5–5 cm long and 0.4–1.2 cm wide
narrowly oval or lance shaped
smooth or shallowly toothed along the edges
usually densely covered with short, curved hairs, becoming hairless with age
on stalks 3–20 mm long
in opposite pairs along the stems.

Flowers are:

pale blue or occasionally lilac
7–10 mm long
tubular
towards the ends of the branches
divided into 2 lips (like petals) the lower lip is about twice as long as the upper lip
present from October to May.

Fruit:

are capsules
split into 4 sections each with one seed.

Seeds are:

fawn or cream coloured
2.5–3 mm long and up to 1 mm wide
smooth
angular.

Stems are:

grey green
square in cross section
densely covered with short hairs
up to 60 cm long but often shorter.

Similar looking species

The native Australian plant, Austral sage (Salvia plebeia) looks similar. Its leaves have shallow, rounded teeth on the margins. The violet, purplish or blue flowers are smaller, only 3.5–5 mm long.

Where is it found?

Mintweed grows in all regions of NSW.

Mintweed is native to North America. It may have been introduced to Australia in contaminated hay.

What type of environment does it grow in?

Mintweed grows in semi-arid, temperate and subtropical climates. Usually, plants grow in fertile clay soils, especially grey, cracking clay. They occasionally grow on lighter soils in flood plains.

Mint weed grows in:

cultivated land especially amongst grain crops
pastures (especially if rundown) and grasslands
disturbed areas including roadsides and trails
floodplains
scrubland, forests and woodlands.

How does it spread?

Mintweed plants can start producing seeds within 6-8 weeks of germinating. They usually germinate from August to March. Even very small plants (5-8 cm tall) can produce seeds. Most seed falls close to the parent plants. Seeds can spread further:

by moving water
in mud adhering to animals, humans or machinery
in contaminated agricultural produce or pasture seed.

References

Everest, S. L. (1981) Poisonous plants of Australia. Angus and Robertson Publishers.

Mc Barron, E.J. (1983). Poisonous Plants: Handbook for Farmers and Graziers. Department of Agriculture NSW.

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

Williams, Cecil Harold, and Herbert John Garnham Hines. "The toxic properties of Salvia reflexa." (1940).

More information

Control

Successful weed control relies on follow-up after the initial efforts. Check regularly at least every 6 weeks so that plants can be controlled before they start producing seeds.

Pasture management

Mintweed can be supressed by maintaining vigorous perennial pastures.

Physical control

Small infestations may be dug out by hand.

Herbicide control

Spray actively growing plants. Ensure all the foliage is covered.

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 amine 625 g/L (Various products)
Rate: 1.1 L/ha
Comments: Boom spray application
Withholding period: 7 days withholding for grazing
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: High volume spot spray. Use the lower rate for plants up to 15 cm tall. Use the higher rate for plants higher than 15 cm.
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. Apply to actively growing plants. Use the lower rate for plants up to 15 cm tall. Use the higher rate for plants higher than 15 cm.
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: 75-100 mL per 15 L of water
Comments: Spot spray from a knapsack. Use the lower rate for plants up to 15 cm tall. Use the higher rate for plants higher than 15 cm.
Withholding period: Nil.
Herbicide group: 9 (previously group M), Inhibition of 5-enolpyruvyl shikimate-3 phosphate synthase (EPSP inhibition)
Resistance risk: Moderate

MCPA 500 g/L (Various products)
Rate: 2.0 L/ha
Comments: Boom spray application for actively growing seedlings.
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

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 2026