Hairy Buttercup (Ranunculus sardous)
Hairy buttercup is a small annual weed that often appears in damp, patchy, or compacted areas of lawns. It germinates in autumn, grows through winter, and flowers in spring, producing large numbers of seeds before dying off in early summer.
Although more common in paddocks and roadside grass, it can easily invade home lawns, especially those that stay wet through winter or are poorly maintained. Once it flowers, hairy buttercup releases thousands of seeds that sit dormant in the soil, ready to germinate again when conditions are right.
The plant’s leaves and stems contain mild toxins that make it unpalatable to livestock, which is why it can dominate dairy pastures — but in lawns, its main impact is visual, forming small clumps that stand out from surrounding grass.
Identification
Hairy buttercup grows in low clumps up to 20–40 cm tall. The leaves are divided into three lobed leaflets, which can be either distinctly separated or partially fused together depending on growth conditions. The foliage and stems are lightly hairy, giving the plant a slightly rough texture.
When in flower, it’s easy to identify by its bright yellow petals and reflexed sepals (the small green parts beneath the petals that bend backward once the flower opens). This feature clearly separates it from creeping or giant buttercup, whose sepals stay upright.
Unlike creeping buttercup, hairy buttercup doesn’t spread by stolons — it reproduces only from seed. The plant prefers cool, moist soil and is often found in lawns that are shaded, compacted, or have poor drainage.
Why It’s a Problem in Lawns
Hairy buttercup competes with grass for light and nutrients during the cooler months when lawn growth slows. Because it germinates in autumn and thrives through winter, it can take advantage of thin, worn areas of turf and quickly fill gaps.
Its flowers and coarse leaves disrupt the smooth, even look of lawns, and if left to seed, it will keep reappearing year after year. Areas that stay damp or receive poor sunlight are especially vulnerable.
Control in Home Lawns
Since hairy buttercup is an annual, it’s easier to manage by targeting seedlings before flowering and maintaining strong grass cover through autumn and winter.
Best control methods:
- Physical removal: Hand-pull small infestations before flowering. It pulls out easily when soil is moist.
- Chemical control: Use selective turf herbicides containing MCPA, dicamba, or picloram/triclopyr (NZLA Gold) for effective control. Flumetsulam (found in some professional turf herbicides) is also effective on seedlings.
- Timing: Spray in late autumn or early winter while plants are young and actively growing.
- Cultural control: Improve lawn drainage, aerate compacted soil, and maintain a thick sward to prevent seed germination in bare patches.
Prevention Tips
- Keep lawns dense with regular overseeding and fertilising.
- Avoid overwatering during cooler months.
- Aerate poorly drained areas to improve soil oxygen.
- Mow regularly through spring to prevent seed heads forming.
- Reseed any bare areas promptly after removing weeds.