Biosecurity Spotters logo

Mintweed (Salvia reflexa)

Mintweed can rapidly invade disturbed or stressed pastures, compete with pasture and crop plants, and contaminate seed and grain. It can also poison stock, taint milk and spread across farms in contaminated produce or on vehicles and animals.

Key facts

Type: Weed, herb.

Native to: North and possibly South America.

Established in: QLD, NSW, ACT, SA, WA.

Other names: Mint Weed, Lanceleaf Sage, Narrow-leaf Sage, Wild Mint.

Best time to act: Look for seedlings after moisture from August to March, especially during the spring and late summer to early autumn germination peaks, and act before plants set seed.

Identification

  • An upright, much-branched annual herb or sub-shrub, usually up to 60 cm tall, with a strong minty or sage-like smell when crushed.
  • Its grey-green stems are four-angled and often densely covered in short, stiff hairs; bluish-green leaves grow in opposite pairs and are narrow, 1.5–6 cm long and 3–12 mm wide.
  • Pale blue, sometimes whitish, tubular flowers grow in opposite pairs or clusters along unbranched spikes at branch ends.
  • The fruit splits into four seed-like nuts; the seeds are smooth, angular and 2–3 mm long, and yellowish grey, tan brown, fawn or cream coloured.
  • Look-alike: Wild Sage or Vervain (Salvia verbenaca) has similar blue-purple to lilac flowers but is perennial and has rough, lobed, deeply veined leaves.
  • Look-alike: Golden Salvia (Salvia aurea) is a perennial shrub with rusty-brown flowers; native Austral Sage or Common Sage (Salvia plebeia) is perennial with scalloped leaves and clusters of violet, purplish or blue flowers along branched stems.

Where it grows

In Australia it occurs mainly from central and south-eastern Queensland to north-eastern New South Wales, with scattered or localised occurrences in other parts of New South Wales, Victoria, South Australia and Western Australia, in disturbed pastures, crop land, roadsides and waste places.

Why it matters

  • It colonises disturbed soils and can replace valued pasture species in overgrazed, frequently flooded or cultivated pastures, and compete with winter cereals, sorghum, maize and cotton.
  • It competes effectively with winter-growing Phalaris aquatica pastures; rain can also release substances from leaf glands that adversely affect crop and pasture seedling germination and growth.
  • Its seed contaminates pasture seed and crops, including wheat grain.
  • It can cause fatal nitrate poisoning in sheep and cattle, particularly when hungry stock enter dense infestations or eat dried plants; it can also taint milk.

How it spreads

  • Mintweed reproduces prolifically by seed, most of which falls within or close to existing patches.
  • Water run-off and mud on animal hooves and pelts, footwear, farm machinery and other vehicles can carry seed farther afield.
  • Seed can also spread as a contaminant of agricultural produce, pasture seed and cereal hay.

Control options

  • Control options include cultivation, summer cropping and the appropriate use of registered herbicides.
  • Reapply herbicide sprays as new seedlings emerge, and prevent stock access to sprayed pastures.
  • Establish and maintain vigorous summer-growing perennial pastures, such as lucerne or vigorous grasses including Tall Finger Grass (Digitaria eriantha).
  • In native pastures, light grazing and topdressing can increase pasture vigour and help suppress Mintweed.

Hygiene and washdown

  • Clean footwear, farm machinery and vehicles before moving from infested patches, as seed can be carried in mud or on equipment.
  • Check pasture seed, agricultural produce and cereal hay for contamination before moving them.
  • Inspect and clean vehicles, plant and footwear before leaving an infested area, paying attention to tyres, radiators, belly plates, tracks and floor mats.
  • Wash down at a designated bay where runoff is contained and can be monitored for seedlings.
  • Record each washdown so the client has evidence of clean entry and exit.

Classification by state

  • Australia (national): No national listing. Managed under state and territory law.
  • Queensland: Not prohibited or restricted. Not listed as prohibited or restricted matter in Queensland. Everyone must also take all reasonable and practical steps to minimise its risks (the general biosecurity obligation).
  • New South Wales: Not a priority weed. Not a state or regional priority weed in NSW. The general biosecurity duty applies: anyone dealing with it must prevent, eliminate or minimise the risk it poses.
  • Victoria: Not declared. Not declared under the Catchment and Land Protection Act 1994. Other Victorian laws may still apply.
  • South Australia: Not declared. Not declared under the Landscape South Australia Act 2019. Other laws may still apply.
  • Western Australia: Permitted, not declared. Listed as a permitted organism in WA, so it can be brought in, but it is not a declared pest.
  • Tasmania: Not declared. Not a declared weed in Tasmania. Other laws may still apply.
  • Northern Territory: Not declared. Not on the NT A to Z weed list, and Weeds Australia does not list it as declared in the NT. Check the NT declared weeds list before moving or planting it.
  • Australian Capital Territory: Not declared. Not declared under the Biosecurity Act 2023 (ACT). A general biosecurity duty still applies.

Legal obligations

Every state and territory places a duty on landholders and people working on land to prevent the spread of invasive species, such as the general biosecurity obligation in Queensland and the general biosecurity duty in New South Wales. Declarations and control requirements differ between states and local government areas, so check the current official list before work starts.

  • Queensland: Biosecurity Act 2014 (Qld), administered by Biosecurity Queensland (13 25 23)
  • New South Wales: Biosecurity Act 2015 (NSW), administered by NSW Department of Primary Industries and Regional Development
  • Australian Capital Territory: Biosecurity Act 2023 (ACT), administered by ACT Biosecurity
  • South Australia: Landscape South Australia Act 2019 (SA), administered by the regional landscape board
  • Western Australia: Biosecurity and Agriculture Management Act 2007 (WA), administered by the WA Department of Primary Industries and Regional Development

Sources