Stinking Mayweed (Anthemis cotula)
Stinking mayweed is an upright, daisy-like annual weed that appears in spring and summer, most often where lawns are thin or patchy. It thrives in dry, compacted, or disturbed soil and quickly colonises open ground left bare after renovation or drought stress.
It produces fine, feathery foliage and white flowers with bright yellow centres. When crushed, the leaves give off a strong, unpleasant odour — one of the easiest ways to identify it.
In home lawns, it stands out sharply against turf because of its upright stems and coarse, uneven growth habit. Once mature, it develops a deep taproot and releases large numbers of seeds that can survive in the soil for several years, allowing it to reappear each spring if conditions are favourable.
Identification
Stinking mayweed has finely divided, fern-like leaves and white ray florets surrounding a yellow central disc. Plants grow to around 20–50 cm tall with a tough, wiry stem that branches near the top.
It’s easily confused with scentless chamomile (Tripleurospermum inodorum), which looks similar but lacks the strong smell, and pineapple weed (Matricaria discoidea), which has no white petals and gives off a sweet, pineapple scent when crushed.
Stinking mayweed flowers throughout spring and summer, producing many small seeds that are spread by wind, mowing, and foot traffic.
Why It’s a Problem
Stinking mayweed competes strongly with desirable turf species, especially in lawns that are thin or under stress. Its deep taproot gives it a competitive edge in dry soil, and its upright stems create an uneven surface and disrupt the uniform look of a well-kept lawn.
Because livestock avoid eating it, stinking mayweed can also become dominant in grazed paddocks and create bare patches where desirable grasses have been shaded out. Once it sets seed, reinfestation is almost guaranteed unless the lawn is thickened and maintained.
Management and Prevention
Long-term control depends on improving lawn health and preventing the conditions that favour stinking mayweed. Focus on building turf density, reducing bare soil exposure, and maintaining consistent growth through the warmer months.
Cultural control methods:
- Maintain dense turf cover: A thick, healthy lawn shades the soil surface and prevents seed germination. Overseed thin areas in autumn or spring.
- Regular mowing: Mow before flowering to prevent seed set. Keep blades sharp to reduce damage to surrounding turf.
- Fertilise effectively: Balanced nutrition improves lawn recovery and reduces open spaces where mayweed can establish.
- Aerate compacted areas: Relieve compaction to improve root growth and turf competitiveness.
- Water management: Avoid letting lawns dry out excessively, as stinking mayweed thrives in stressed turf.
Manual control:
Hand removal is effective for small infestations, particularly before flowering. Ensure the entire taproot is removed to prevent regrowth.
Chemical Control:
Stinking mayweed is only moderately sensitive to many common lawn herbicides. Best results are achieved when weeds are treated early, while still young and actively growing.
- Effective active ingredients include:
- Bentazone (e.g. Basagran, Pulsar)
- Flumetsulam (e.g. Preside)
- Thifensulfuron (e.g. Harmony)
Limited control:
- MCPA, MCPB, and 2,4-D generally give poor results.
In established lawns, use selective broadleaf herbicides containing one or more of the effective actives above, and always follow product label directions carefully. Strengthening turf cover after spraying will prevent reinfestation from seed.