Quick Facts

Quick facts

• Mintweed (Salvia reflexa) is an annual herb growing up to 60 cm high (sometimes more), with opposite, narrow, greyish, felt-like leaves, pale blue flowers in interrupted spikes and a strong minty aroma.
• It is spread by seed, which it produces prolifically.
• It is a weed of crops, pastures, roadsides and wasteland.
• It can be toxic to stock.

What Does It Look Like?

What is it?

Mintweed (Salvia reflexa) is an upright, much-branched annual herb or sub-shrub growing up to 60 cm high, sometimes taller but often much shorter. It has a strong minty or sage-like odour when crushed or broken. The stems and branches are grey green, four-angled in cross-section and are often densely covered with short, stiff hairs. The bluish green leaves occur in opposite pairs. The leaf blade is narrowly egg-shaped to narrowly oval in shape, 1.5-6 cm long and 3-12 mm wide. The lower surface is greyish and usually densely covered with short hairs; the upper surface becomes hairless with age. The leaves have tiny glands on both surfaces. The flowers are in opposite pairs or clusters (whorls) of 3 or 4 at intervals in unbranched spikes at the ends of the branches. The flower is tubular, pale blue or sometimes whitish, 7-12 mm long and 2-lipped with the lower lip about twice as long as the upper lip and weakly 3-lobed. The fruit is a 4 lobed capsule that splits into 4 seed-like nuts. Seeds are yellowish grey, tan brown, fawn or cream coloured, smooth, angular and 2-3 mm long (Everist 1974; Kleinschmidt & Johnson 1977; Friend 1983; Wheeler 1987; Felfoldi 1993; Cunningham et al. 1992; Hussey et al. 1997; Parsons & Cuthbertson 2001; Richardson et al. 2006).

For further information and assistance with identification of Mintweed, contact the herbarium in your state or territory.

Flower colour

Blue, White

Growth form (weed type/habit)

Shrub, Herb

Where it currently grows? Preferred habitat

Mintweed occurs in disturbed semi-arid, temperate and subtropical open scrub, grasslands and sometimes forests (open dry sclerophyll forest to rainforest), mainly on fertile clay soils, occasionally on lighter soils subject to flooding. It is common on floodplains in grey cracking clays. It is a weed of cultivation, run-down pastures, roadsides and waste places (Kleinschmidt & Johnson 1977; Conn 1992; Cunningham et al. 1992; Parsons & Cuthbertson 2001).

Are there similar species?

The weed Wild Sage or Vervain (Salvia verbenaca) is an upright herb with blue-purple to lilac flowers, like Mintweed, but it differs in being a perennial with rough, lobed, deeply-veined leaves. The weedy Golden Salvia (S. aurea) is a perennial shrub up to 1.5 m high with rusty-brown flowers, while the native Austral Sage or Common Sage (S. plebeia) is a perennial herb up to 90 cm high with scalloped leaf edges with small, rounded teeth and clusters of 2-10 violet, purplish or blue flowers along branched stems. The weed Salvia misella (previously called Salvia riparia) has blue flowers, but it is a perennial herb up to 1 m high with leaves up to 4 cm wide (Stanley & Ross 1986; Hussey et al. 1997; Conn 1992, 1999).

Why Is It A Weed?

What are its impacts?

Mintweed is a rapid coloniser of disturbed soils. It can invade pastures that have been stressed by overgrazing, frequent summer flooding or cultivation and replace valued pasture species. It may also compete with and reduce the yields of winter cereals, sorghum, maize and cotton. Although not usually a serious weed of wheat crops, its seed will still contaminate the wheat grain. Its seedlings are only weakly competitive and rarely invade vigorous established pastures. However, Mintweed does invade and compete very effectively with winter growing Phalaris aquatica pastures. Dry winters followed by wet summers provide optimal conditions for an explosive spread of the weed in disturbed pastures, where it can quickly take over. Rain also liberates allelopathic substances (chemical inhibitors) from minute bladder-like structures (glands) on the leaves, which have adverse effects on the germination and growth of seedlings of crop and pasture species (Cunningham et al. 1992; Felfoldi 1993; Parsons & Cuthbertson 2001).

Mintweed seed can contaminate pasture seed and is often found in seed of millet, sorghum, panic, lucerne, Vigna, Rhodes Grass, Phalaris, Buffel Grass, oats and Urochloa (Friend 1983).

Mintweed can be toxic to stock. It may be eaten by hungry stock and has been reported to have caused fatal nitrate poisoning in sheep and cattle. It is particularly a hazard when hungry animals are introduced for the first time to densely infested pastures or, in winter, when dried plant material has lost much of the strong odour and flavour that previously deterred grazing. There is a risk to animals when travelling along infested stock routes and contaminated cereal hay has caused poisoning (Hurst 1942; Everist 1974; Kleinschmidt & Johnson 1977; Cunningham et al. 1992; Parsons & Cuthbertson 2001). Mintweed will also taint milk (Friend 1983).

How does it spread?

Mintweed reproduces and is spread by seed, which it produces prolifically. While most seed falls within or closely around existing patches, some seed may be transported over greater distances through water run-off or mud sticking to hooves and pelts of animals, or on footwear, farm machinery and other vehicles. Some seed may also be spread as a contaminant of agricultural produce or pasture seed (Friend 1983; Parsons & Cuthbertson 2001).

What is its history in Australia?

Mintweed was first recorded in Australia near Pittsworth, Queensland, at the beginning of the 20th century and is thought to have been introduced during the 1902 drought as a contaminant in fodder from the United States of America. It has since become widespread in south and central Queensland and northern New South Wales, principally on the heavy black and red soils of the open Mitchell Grass and Blue Grass downs and cleared Brigalow and Gidgee scrubs (Parsons & Cuthbertson 2001).

How To Manage It?

Best practice management

Mintweed can be controlled through cultivation, summer cropping and the appropriate use of herbicides, or through the establishment and maintenance of vigorous, summer-growing perennial pastures e.g. lucerne or vigorous grasses such as Tall Finger Grass, Digitaria eriantha [as Digitaria smutsii] (Everist 1974; Cunningham et al. 1992; Parsons & Cuthbertson 2001). In native pastures, light grazing and topdressing increase pasture vigour and help suppress Mintweed (Parsons & Cuthbertson 2001). Herbicides are an effective control measure. However, it is necessary to re-apply sprays each time new seedlings emerge and to prevent stock access to sprayed pastures (Parsons & Cuthbertson 2001).

Please see the Australian Pesticides and Veterinary Medicines Authority for chemical information http://www.apvma.gov.au 

Does it have a biological control agent?

NO

When does it grow? (lifecycle/growth calendar)

Mintweed is an annual, with seed germinating from August to March whenever sufficient moisture is available. Successive germinations occur and, like many summer growing species, it has two germination peaks directly related to improved moisture availability in spring and late summer-early autumn. Young plants flower almost immediately (mainly late spring to autumn), setting copious seed within 6-8 weeks of emergence. Even in dry periods, plants less than 10 cm high flower and set sufficient seed to ensure survival. Plants persist through summer and normally die in late autumn or early winter (Kleinschmidt & Johnson 1977; Conn 1992, 1999; Parsons & Cuthbertson 2001).

Where Is It Found?

Which states and territories is it found?

NSW, QLD, SA, VIC, WA

What areas within states and territories is it found?

Mintweed occurs mainly from central and south-eastern Queensland to north-eastern New South Wales, but also occurs as scattered plants or localised dense patches in parts of western and southern New South Wales. It is occasionally recorded in central Victoria (as a garden escape in the Culgoa, Castlemaine and Heathcote areas), south-eastern South Australia (near Cleve, Yunta and Port Lincoln) and south-western Western Australia where it is found occasionally around Perth, Kalgoorlie, Coolgardie and Esperance (Toelken 1986; Wheeler 1987; Hussey et al. 1997; Conn 1992, 1999; Parsons & Cuthbertson 2001; AVH 2008).

Where does it originate?

Mintweed is a native of North and possibly South America (Parsons & Cuthbertson 2001).

National And State Weed Listings

Is it a Weed of National Significance (WONS)?

NO

Where is it a declared weed?

NSW, WA

Government weed strategies and lists – Weeds Australia

Is it on the National Alert List for Environmental Weeds?

NO

Government weed strategies and lists – Weeds Australia

Is it on the Agricultural Sleeper List?

NO

Government weed strategies and lists – Weeds Australia

Names And Taxonomy

Main scientific name

Salvia reflexa

Other scientific names (synonyms)?

• Salvia lanceaefolia Poir. (incorrect spelling)
• Salvia lanceifolia Poir.
• Salvia lanceolata Brouss.

Does it have other known common name(s)?

Mint Weed, Lanceleaf Sage, Lance-leaf Sage, Narrow-leaf Sage, Narrow-leafed Sage, Wild Mint, Blue Salvia