Wireweed (Polygonum aviculare)
Wireweed is a low-growing summer annual weed that often sneaks into bare or compacted areas of lawns. It belongs to the same family as willow weed but appears much earlier in spring, especially in wet or compacted soil where desirable grasses struggle to germinate.
You’ll most often find it spreading across driveway edges, sports fields, and high-traffic areas where the turf has thinned out. Once established, it forms wiry mats that can survive trampling, mowing, and dry summer conditions, making it a frustrating weed to remove once mature.
Identification
Wireweed produces slender, wiry stems that sprawl along the ground with small, oval leaves spaced evenly along each stem. Each leaf has a papery sheath (called an ochrea) at its base — one of the easiest features to identify it by.
In compacted soil or along paths, wireweed often hugs the ground and stays small. In better conditions, it can grow more upright and leafy. Tiny greenish-pink flowers appear at the base of the leaves rather than at the tips of the stems, so they’re easy to miss.
A related species, small-leaved wireweed (Polygonum arenastrum), looks nearly identical but stays smaller and more compact. Both are common in New Zealand and respond similarly to control measures.
Why It’s a Problem in Lawns
Wireweed thrives where lawns are stressed — compacted, patchy, or overwatered. Because it sits flat and forms dense mats, it competes aggressively for moisture and space, preventing grass from re-establishing.
Its wiry stems can tangle in mower blades, and its ability to withstand heavy foot traffic makes it particularly stubborn in sports turf and playground areas. Once it matures, the plant becomes highly resistant to many broadleaf herbicides, which is why early treatment is key.
Control in Home Lawns
Wireweed is easiest to remove while it’s young and actively growing in spring or early summer. Once mature, it becomes tougher to kill and may need multiple treatments.
Best control methods:
- Physical removal: Hand-pull seedlings before they spread. The roots are shallow but strong, so use a weeding knife to lift them cleanly.
- Chemical control: Use selective turf herbicides containing MCPA, dicamba, or picloram/triclopyr (NZLA Gold) for established infestations. Apply when the weed is at the seedling stage for best results.
- Avoid overwatering: Wireweed favours moist, compact soil. Fixing drainage and reducing irrigation frequency will help prevent re-growth.
- Improve lawn density: Aerate compacted areas, fertilise, and overseed to crowd out new seedlings before autumn.
Prevention Tips
- Keep lawns dense and healthy to reduce bare patches.
- Aerate and topdress compacted areas each spring.
- Don’t mow too short — a slightly higher mowing height helps shade out weed seedlings.
- Remove wireweed before it sets seed to stop the cycle repeating.