Chickweed (Stellaria media)
Chickweed is a soft, fast-growing annual weed that often appears in New Zealand lawns over autumn and winter. It thrives in cool, moist, and shaded areas, particularly under trees or in lawns that don’t get much sun. Once it establishes, chickweed can form a dense mat that smothers out grass and other plants.
It germinates at almost any time of the year, but it grows most actively through the cooler months. Because it grows quickly and spreads by both seed and creeping stems, chickweed can take over bare or thin patches of lawn in just a few weeks.
While it’s harmless in pastures and easily grazed down by stock, it’s a nuisance in lawns, gardens, and shaded areas where it makes the turf look patchy and untidy.
Identification
Chickweed has small, light green leaves that are oval-shaped with pointed tips. The leaves are smooth and hairless, but the stems are distinctive — they have a single line of fine hairs running along one side.
The plant spreads by creeping stems that root at the nodes, forming dense mats. In spring, it produces clusters of tiny white, star-like flowers at the tips of the stems. These flowers develop into small seed capsules that burst open, releasing large numbers of fine seeds.
A similar species, mouse-ear chickweed, looks almost identical but has much hairier leaves and stems.
Why It’s a Problem in Lawns
Chickweed grows quickly and smothers thin or shaded turf, particularly in moist areas where grass struggles. It thrives in cool conditions when lawn growth slows, making it a common winter invader.
Because it grows low to the ground and forms dense mats, mowing has little effect. It also produces huge amounts of seed that remain viable in the soil, so even if it dies off in summer, new seedlings often appear again the following autumn.
Control in Home Lawns
Chickweed is relatively easy to control in lawns if treated early before it flowers and sets seed. It’s sensitive to many broadleaf herbicides, but timing and lawn recovery are important to prevent reinfestation.
Best control methods:
- Physical removal: For small patches, hand-pull the weed or use a weeding knife to lift the shallow roots. It pulls easily from damp soil but can regrow if roots are left behind.
- Chemical control: Use a selective herbicide containing mecoprop, which is very effective on chickweed. Turf herbicides based on triclopyr (NZLA Gold) also work well. Avoid products containing only MCPA or 2,4-D, as chickweed is tolerant to these.
- Prevention: Keep the lawn thick and healthy through autumn to block new seedlings. Overseed shaded or compacted areas where chickweed tends to appear.
Prevention Tips
- Fertilise and overseed thin lawns before winter to strengthen grass cover.
- Aerate shaded or compacted soil to improve drainage and sunlight exposure.
- Avoid overwatering—chickweed loves damp, shaded conditions.
- Regular mowing helps reduce seed formation, but avoid scalping.
- Remove any existing mats before they flower to stop reseeding.