Cudweed (Gamochaeta spp.)
Cudweed is a group of small, low-growing weeds that often appear in dry or compacted New Zealand lawns. Several species are found nationwide, commonly referred to as Purple Cudweed, Silky Cudweed, Japanese Cudweed, and Jersey Cudweed. These species can behave as annuals, biennials, or short-lived perennials depending on conditions.
Cudweeds have a distinctive grey-green or silvery look caused by fine woolly hairs that cover one or both sides of the leaves. They usually form flat rosettes in lawns before sending up tall, wiry stems covered in small clusters of flowers. Because of their tough, fibrous growth habit and tolerance to close mowing, they can quickly become a nuisance in thin or neglected turf.
Identification
Cudweed species all share similar traits, making them easy to recognise once you know what to look for.
Purple Cudweed (Gamochaeta coarctata)
Forms a rosette of shiny, hairless basal leaves (20–110 mm long) that are widest near the tip, with white woolly hairs underneath. Small whitish flower heads (around 3 mm wide) appear from September to March along upright stems.
Gamochaeta purpurea
Similar to Purple Cudweed but with hairs on both sides of the leaves. Less common and mainly found in the North Island.
Silky Cudweed (Gamochaeta calviceps)
Has long, thin pale-green leaves and a much-branched, spreading habit. Flowers are diffuse and pale, and it is widespread throughout New Zealand.
Gamochaeta subfalcata
Also called Silky Cudweed, but with fewer basal branches and bright reddish-purple flower bracts. It favours waste areas and coastal sites in the upper and lower North Island.
Japanese Cudweed (Euchiton sphaericus)
Native to New Zealand, this species has dense spherical flower heads (about 2 cm wide) with four small leaves immediately beneath each cluster. It’s common in drier regions receiving less than 1000 mm of annual rainfall.
Jersey Cudweed (Pseudognaphalium luteoalbum)
Easily recognised by its thick woolly leaves on both sides and small brown-yellow flowers clustered on stems up to 50 cm tall. The entire plant often appears silver when mature and is found in lawns, gardens, pastures, and disturbed ground throughout the country.
Why It’s a Problem in Lawns
Cudweed thrives in dry, compacted, or low-fertility lawns, especially where grass coverage is weak. It spreads by seed and forms tight mats that crowd out desirable turf species. Its silvery, fuzzy foliage gives the lawn a patchy appearance, and once flowering stems form, the plant can reseed heavily.
Because cudweed tolerates mowing and many common turf herbicides, it can persist year after year if not treated properly. Its presence is often a sign the lawn needs better soil aeration and nutrition.
Control in Home Lawns
Cudweed can be controlled effectively with the right approach, but early treatment, before flowering is key.
Best control methods:
- Physical removal: Hand-weed small patches before they flower. Remove the full root to prevent regrowth.
- Chemical control: Herbicides containing amitrole or dicamba (sold as Banvine or Bandit) are effective for selective control in turf. Apply while plants are actively growing, ideally before flowering begins.
- Cultural management: Regular fertilising, proper mowing height, and aeration reduce compacted conditions that favour cudweed. A dense, healthy lawn canopy will prevent new seedlings from establishing.
Prevention Tips
- Maintain steady soil fertility with balanced lawn fertilisers.
- Aerate compacted areas to improve air and water movement.
- Water deeply but infrequently to encourage deep grass roots.
- Reseed thin areas in autumn to keep turf dense and competitive.
- Remove flower heads before they seed to stop reinfestation.