Fleabanes

Scientific name: Conyza sumatrensis, Conyza bonariensis

Wavy-leaved fleabane (Conyza bonariensis)

Wavy-leaved fleabane (Conyza bonariensis)

Broad-leaved fleabane (Conyza sumatrensis)

Broad-leaved fleabane (Conyza sumatrensis)

Wavy-leaved fleabane (Conyza bonariensis)

Wavy-leaved fleabane (Conyza bonariensis)

Broad-leaved fleabane (Conyza sumatrensis)

Broad-leaved fleabane (Conyza sumatrensis)

Broad-leaved fleabane (Conyza sumatrensis)
  • Key characteristics
  • Biology
  • Impacts
  • Control
  • Further information

  • Both species have low-growing winter rosettes and in summer produce tall flower stalks that only branch below the flowers
  • The numerous flower heads are small (2-3 mm across) and unattractive, whitish, cream or sometimes reddish in colour
  • Both species are annual or biennial and are unpalatable to stock, therefore, the flower stalks stand out in pastures in late summer and autumn
  • Both species are found, often growing together, in cultivated land, pasture, waste places, sand dunes, roadsides and industrial areas
  • The species are easily separated at the rosette stage by the narrow crinkly or wavy leaves of wavy-leaved fleabane and when flowering by the larger, whiter, ball-like flower heads of wavy-leaved fleabane.

Broad-leaved fleabane (Conyza sumatrensis)

  • The most common of the fleabane species in New Zealand and is widespread throughout the country
  • Many small composite flower heads, whitish in colour, each about 2 mm across, appear in lateral clusters towards the top of the flower stalk
  • Seeds are topped by dirty-white to light tan pappus hairs
  • Tall (up to 2 m) flower stems are longitudinally ridged, densely hairy towards the top
  • The basal rosette leaves are flat, up to 12 cm long by 2 cm wide, thin, soft, very variable in shape. Stem leaves are narrower, without stalks, again variable in shape, with rough surfaces and few or many hairs.

Wavy-leaved fleabane (Conyza bonariensis)

  • Found from Auckland southwards, in lowland in the North Island and in Nelson, Marlborough, Canterbury and Central Otago in the South Island
  • It has a shorter flower stalk (up to 1.2 m tall) and its many flower heads are 2-3 mm across, whitish in colour, often becoming reddish later
  • Flower heads are largely enclosed with many calyx sepals, which are often red towards the tips. Seeds are topped with white to cream pappus hairs, sometimes tinged with red towards the tips
  • After opening the seed heads are ball-like and usually white to cream in colour
  • Leaves are blue-green, wavy and usually twisted, covered in stiff hairs; stem leaves are usually narrow, lance-shaped, wavy and twisted.

Similar but much less common species

  • Three other species of Conyza – Conyza bilbaoana, Conyza canadensis, and Conyza parva are found in New Zealand
  • Conyza bilbaoana (Canadian fleabane) has slender, coarsely-toothed, more or less rough leaves, and flower heads 1.5-2.5 mm across, arranged in a long, leafy pyramid. It is found in waste places, riverbeds, cultivated land, and rocky hillsides throughout New Zealand
  • Conyza canadensis (also often known as Canadian fleabane) has long been confused with but is less common than Conyza bilbaoana. The two species are easily distinguished by the shape of the involucral bracts (the tiny leaf-like structures around each flower head) which are sparsely to moderately bristly on both surfaces in Conyza canadensis but hairless in Conyza bilbaoana
  • Conyza parva (smooth fleabane) is a smaller, more slender plant than the other species and is found in only a few places in northern North Island.

Origin

  • All these species originated in the Americas: broad-leaved fleabane in subtropical South America; Canadian fleabane in South America; wavy-leaved fleabane in temperate South America; Conyza canadensis in North America; smooth fleabane in Eastern USA
  • Conyza bilbaoana was first recorded in New Zealand in 1855, Conyza bonariensis in 1883, Conyza parva in 1940, Conyza sumatrensis in 1957, and Conyza canadensis in 1988 (according to the Flora of New Zealand).

Life cycle

  • All these species are annuals or biennials, flowering once in their short lifetimes and then dying
  • Seeds are most likely to emerge in autumn.
  • Seedlings form low-growing rosettes over winter, and these give rise to flowering stems in the spring
  • Seed production in all species is prolific. Seeds are carried for some distance on wind currents and are often found stuck to footwear, farm machinery and vehicles. 

Benefits

  • Fleabanes (in particular Canadian fleabane) are claimed to produce a wide range of beneficial herbal remedies
  • In traditional North American herbal medicine, Canadian fleabane was said to have been used as a snuff and burned to create a smoke that warded off insects. Present day uses as herbal remedies include the treatment of gastro-intestinal problems, such as diarrhoea and dysentery, and as a treatment for bleeding haemorrhoids
  • Given the confusion over the correct botanical names of species of fleabane, it is unclear as to which species may have herbal benefits.

Impact on crops

  • Some of these species are sometimes found on cultivated land and may be found in arable crops, but do not usually cause problems
  • They are more likely to be a problem in permanent crops; for example lucerne and tree crops.

Impact on pasture

  • All these species are found in pasture and, at high density, can interfere with the productivity of grasses and clovers
  • The appearance of tall flower stalks, that are not palatable to livestock, can look very unsightly in otherwise neat, tidy pastures.

Impact on the natural environment

  • These species are usually found in grassland or waste places or on bare soil but are sometimes found in places where they may interfere with the regeneration of native species
  • Frequently found on roadsides from where the seed can readily spread to pastures.

Resistance to glyphosate

  • Fleabanes have become resistant to glyphosate herbicide in 14 different countries
  • This poses a great risk also in New Zealand in areas where glyphosate is repeatedly used such as roadsides, railway lines vineyards and orchards.

Grazing management

  • Maintaining vigorous, dense pastures stops the seedlings from establishing. This can be achieved by using pasture species suitable for the local environment, keeping soil fertility at optimum levels, and ensuring grazing management is appropriate for the pasture species used and for the local environment
  • After the flower stems form, they are not palatable to animals. Mowing will knock these down, but will not be a useful control method for those plants growing along fence-lines or in waste areas.

Chemical control

  • Glyphosate is effective on young plants, but seems to be less effective as the plants approach maturity
  • In Australia glyphosate resistance has developed in wavy-leaved fleabane (known to Australians as flax-leaved fleabane), and broad-leaved fleabane may also develop resistance to glyphosate here if sprayed for too many successive years. Broad-leaved fleabane has developed resistance to glyphosate in vineyards and orchards in Europe.
  • Adding simazine or terbuthylazine to the glyphosate spray will give good or adequate control of fleabanes. Both additives have residual action in the soil and will prevent seedlings from emerging for several weeks or sometimes months
  • Clopyralid and dicamba can also be used for fleabane control but both are very damaging to clovers and should not usually be used except for spot application
  • Other herbicides that will control these species include a triclopyr/picloram mix (also suitable for spot-spraying in pastures) or 2,4-D ester for younger plants (if boom-spraying of pastures is considered necessary)
  • In orchards, in addition to the use of glyphosate, both glufosinate and amitrole give reasonable control
  • As well as resistance to glyphosate, fleabanes have also developed resistance to sulfonylureas, paraquat and atrazine in many countries; herbicide avoidance strategies should always be used.

  • Popay I, Champion P, James T 2010. An illustrated guide to common weeds of New Zealand. New Zealand Plant Protection Society, Christchurch, New Zealand. 416 p.