Starweed (Stellaria media)
Starweed, also known as chickweed, is a fast-spreading annual weed that thrives in damp, shaded lawns and compacted soils. It establishes easily in bare or thin turf and can smother fine grasses with its dense, mat-like growth.
It germinates throughout autumn and winter, forming small, soft green leaves and delicate white star-shaped flowers that appear almost year-round in mild conditions. Once established, it can spread rapidly by seed and creeping stems, especially in well-watered or shaded areas.
In home lawns, starweed spoils the uniform appearance of turf and creates a spongy surface that’s difficult to mow cleanly. It also competes heavily with slower-growing grasses during cool, moist periods.
Identification
Starweed forms low, sprawling mats of smooth, bright green foliage. The stems are slender, branched, and often have a single line of fine hairs running along one side — a key identifying feature.
Leaves are small, oval, and opposite along the stem, with the upper leaves stalkless. Small white flowers with five deeply notched petals give the appearance of ten petals when viewed from above.
Because of its soft growth, starweed is easily pulled by hand, but if left unchecked, it can produce thousands of seeds per square metre, ensuring rapid reinfestation.
Why It’s a Problem
Starweed competes with turfgrasses for light, water, and nutrients, especially during cooler months when grass growth is slow. It can tolerate close mowing and spreads quickly into any open patch of soil, making it difficult to eradicate once mature.
In wet or shaded lawns, it can dominate completely, leaving little room for desirable grasses to recover. Its prolific seed production ensures that once it appears, it often returns each year unless the underlying conditions are corrected.
Management and Prevention
Healthy, well-drained lawns are far less likely to develop starweed infestations. The best long-term solution is to focus on maintaining strong turf cover and reducing excessive moisture or shade.
Cultural control methods:
- Improve drainage: Starweed thrives in damp, compacted soil. Aerate regularly and topdress with sand to improve surface drainage.
- Maintain dense turf: Overseed bare areas to close gaps where weed seeds can germinate.
- Mow regularly: Frequent mowing prevents flowering and seed set.
- Reduce shade: Trim trees and shrubs to increase sunlight and improve drying.
- Avoid overwatering: Keep irrigation light and infrequent to discourage wet soil conditions.
Manual control:
Small patches can be hand-weeded, ensuring the entire root system is removed. Dispose of pulled weeds before they set seed.
Chemical Control:
A combination of hand weeding and chemical control is often required to eliminate starweed completely.
Repeat herbicide applications 3–6 weeks apart will usually provide full control.
Effective herbicides include:
Triclopyr/picloram mixtures (NZLA Gold) provides strong results in established lawns.
Apply when weeds are actively growing, and always follow product label directions. Strengthening turf density after treatment will reduce the chance of re-establishment.