Cudweeds

Scientific name: Gamochaeta spp., Euchiton sphaericus and Pseudognaphalium luteoalbum

Gamochaeta coarctata (purple cudweed)

Pseudognaphalium luteoalbum (Jersey cudweed)

Gamochaeta simplicicaulis

(Soft rush) Juncus effusus u

Gamochaeta coarctata (purple cudweed)

Gamochaeta coarctata (purple cudweed)

Gamochaeta calviceps (silky cudweed)

Euchiton sphaericus (Japanese cudweed)

Euchiton sphaericus (Japanese cudweed)

Euchiton sphaericus (Japanese cudweed)
  • Key characteristics
  • Biology
  • Impacts
  • Control
  • Further information

  • The cudweeds include several species similar in growth habits and control measures. In general, the cudweeds have one to many basal rosettes with leaves and seedheads that are covered in distinct fine, white “woolly” fibres. Some species only have this hair on the undersides of the leaves, while others have it on both surfaces. Cudweeds overwinter as small basal rosettes, but in the spring usually grow an upright stem on which flower heads appear. All are members of the daisy family, with many small flowers in each flower head
  • Gamochaeta coarctata (purple cudweed) is one of the more common cudweeds. It is very variable but always has stalkless leaves with shiny, hairless upper surfaces and white woolly hairs on the lower surface. The basal leaves die off before flowering but those on the flowering stem remain. Small whitish flower heads occur in dense clusters along the erect flowering spikes. It is common throughout the North Island and in parts of the South Island, growing in many habitats including as a weed in lawns and crops
  • Gamochaeta purpurea is similar to G. coarctata buthas leaves that are hairy on both surfaces. It is not common and is only found in the North Island
  • Gamochaeta simplicicaulis has wavy-edged leaves and thick flower stalks with a leafy inflorescence, and is not common in northern parts of the North Island
  • Gamochaeta calviceps (silky cudweed) can usually be distinguished by its long thin (sometimes spatulate shaped) leaves with pale green colouration on both surfaces. It has a much-branched growth habit, diffuse, pale inflorescences and is locally common throughout New Zealand
  • Gamochaeta subfalcata (also called silky cudweed) is very similar to G. calviceps but has only a few basal branches and bright reddish-purple flower bracts. It is mostly found in waste places and coastal sites in Northland, Auckland, Coromandel and Wellington
  • Euchiton sphaericus (Japanese cudweed) is native to New Zealand, and has dense spherical flower heads, each about 2 cm in diameter, with four leaves immediately below it, at the top of upright stems about 20 cm long. It is common throughout New Zealand in lower rainfall areas (below 1000 mm)
  • Pseudognaphalium luteoalbum (Jersey cudweed) is thickly woolly on both leaf surfaces and has many basal stems, each with many narrow leaves. It has small brown-yellow flowers in dense clusters on 50 cm tall stems and at maturity the whole plant may be quite silver in colour. It is native to New Zealand and is found in many countries and occurs in lawns, gardens, pasture and cultivated areas throughout New Zealand.

Origin and habit

  • Most of our cudweeds were introduced from North or South America or elsewhere in the world, but two species (see above) are thought to be native to New Zealand
  • Some species are common throughout New Zealand, but others are more restricted in their distribution
  • They grow in a range of habitats and some are common in lawns, gardens, pastures, and cultivated land
  • Some species were first recorded in New Zealand over 100 years ago, but others have only appeared here more recently
  • The common name “cudweed” was used because such species were once used to feed to cows which had lost the ability to chew their cud.

Life cycle

  • Cudweed seeds are generally very small and do not emerge if covered by more than a few millimetres of soil
  • All are annuals, biennials or short-lived perennials with flattened basal rosettes in winter and upright flower stems that appear in spring and summer
  • The leaves are covered with woolly hairs on one or both leaf surfaces. The flower heads are small and each head contains many tiny flowers.

Benefits

  • The caterpillars of some species of butterflies use the leaves for food.

Impact on crops

  • Some species of cudweeds grow in cropping situations and reduce the nutrients and water available to the crop
  • Because of their fast growth and ability to spread they can be very competitive at high densities
  • Jersey cudweed (Pseudognaphalium luteoalbum) has sometimes been a problem in asparagus production because of its tolerance to commonly used herbicides.

Impact on pasture

  • Cudweeds usually occur in thin open pastures and their prostrate rosettes may interfere with the growth of grasses.
  • Cudweeds are also a major problem in lawns and turfs which are regularly mown. Their prostrate habit means they usually avoid the mower blades and the frequently cut grasses offer little competition.

Grazing management

  • Pastures should be kept dense in autumn to prevent cudweeds becoming established. This can be done by selection of appropriate grass cultivars or by grazing management.

Chemical control

  • Quick knock-down of cudweeds in waste places or before crops have emerged can be achieved with glyphosate or glufosinate-ammonium
  • Many herbicides commonly used for long-term control of weeds in asparagus (like dicamba, clopyralid, metsulfuron-methyl, simazine, and tribenuron-methyl) are not effective on Jersey cudweed
  • Diuron plus amitrole or linuron have proved to be the most effective herbicides for control of Jersey cudweed in asparagus
  • On mature Jersey cudweed plants amitrole, simazine plus amitrole or dicamba killed the plants but new seedlings quickly emerged.

Integrated control

  • Dense, well-fertilised pastures are much less likely to be invaded by any of these cudweeds
  • Rotation of different classes of herbicide in crops like asparagus will reduce the possibility of cudweeds increasing due to their tolerance of some herbicides.

  • 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.