Creeping Oxalis (Oxalis exilis)
Creeping oxalis is one of the most common and persistent weeds found in New Zealand lawns. It’s a small, low-growing perennial that spreads through fine stolons (creeping stems) which root at the nodes, forming dense mats that can quickly overtake thin or patchy turf.
Unlike other oxalis species such as pink shamrock (Oxalis vallicola) or Bermuda buttercup (Oxalis pes-caprae), creeping oxalis doesn’t produce underground bulbs. Instead, it relies on its stolons to spread efficiently across the lawn surface. This makes it well adapted to mowing and trampling, allowing it to thrive year-round in most parts of the country.
Creeping oxalis produces small bright yellow flowers that make it easy to spot during its active growth stages. It’s native to New Zealand and tolerates a wide range of conditions—from dry, low-fertility soil to damp, compacted areas. Once established, it’s difficult to remove due to its strong regrowth ability and tolerance to many common lawn herbicides.
Identification
Creeping oxalis has trifoliate leaves, meaning each leaf is made up of three small, heart-shaped leaflets. Each leaflet has a distinct notch at the tip, giving it a clover-like appearance. The leaves are much smaller than those of other oxalis species, typically less than 10 mm across, and sit low to the ground on delicate stems.
During flowering, it produces single yellow, five-petalled blooms that radiate from a central point. Unlike clovers, these flowers are simple and not the pea-shaped florets of legumes.
Creeping oxalis is often confused with horned oxalis (Oxalis corniculata), which looks almost identical but grows slightly larger, with leaves up to 20 mm wide and clusters of two to five flowers. Horned oxalis is more common in gardens and nursery beds, while creeping oxalis is better adapted to lawns and turf areas.
Why It’s a Problem in Lawns
Creeping oxalis is a serious nuisance in lawns because it spreads rapidly through stolons and can survive repeated mowing. Once established, it forms tight mats that smother grass, especially in dry or compacted spots where lawn species struggle to recover.
It’s also resistant to many selective turf herbicides, so even after spraying, regrowth often occurs from the stolon network. Left unchecked, creeping oxalis can take over large sections of lawn within a season. Its small size means it often goes unnoticed until it’s well established.
Control in Home Lawns
Creeping oxalis is one of the harder weeds to eliminate completely, but with the right herbicide and good lawn care practices, it can be brought under control.
Best control methods:
- Physical removal: Hand-pulling is effective for small patches, but all stolons must be removed. Any remaining fragments will quickly re-root and regrow.
- Chemical control: Herbicides containing triclopyr are the most effective option like NZLA Gold.
- Other herbicides: Common turf herbicides containing MCPA, clopyralid (NZLA BWC), or 2,4-D offer poor or temporary results only. Image (mecoprop + ioxynil + bromoxynil) may slow growth but seldom kills the weed completely.
- Cultural management: Improve soil fertility, reduce compaction, and maintain a dense lawn through fertilising and overseeding. A healthy, well-fed lawn will outcompete oxalis seedlings before they spread.
Prevention Tips
- Fertilise regularly to maintain dense grass cover.
- Aerate compacted areas to improve drainage and root growth.
- Reseed thin or bare areas promptly after treatment to prevent new weeds from establishing.
- Avoid mowing too short; scalping the lawn creates open areas that oxalis exploits.
- Check newly established lawns and garden edges regularly—creeping oxalis often spreads from surrounding beds.