Mouse-ear Hawkweed (Pilosella officinarum)
Mouse-ear hawkweed is a low-growing perennial weed that spreads aggressively through stolons, forming dense mats that can choke out turfgrass and other vegetation. Once established, it’s difficult to remove and often appears in lawns, sports turf, and low-fertility areas where grass growth is weak.
Although best known as a serious weed in South Island high country pastures, mouse-ear hawkweed is also becoming more common in urban lawns and roadside turf across both islands. It thrives in dry, compacted, or low-nutrient soils, where regular grass struggles to compete. The plant’s dense growth habit allows it to crowd out desirable species, leaving bare or patchy turf that’s hard to repair.
Identification
Mouse-ear hawkweed forms a rosette of spoon-shaped leaves covered in fine, silvery hairs. The leaves are grey-green on top and pale underneath, giving the plant a distinctive appearance.
From this rosette, it sends out creeping stolons (runners) that root at intervals and produce new rosettes, allowing it to spread across the surface like a creeping mat. In spring and early summer, it produces bright yellow daisy-like flowers on slender, leafless stems. Each flower closes at night or in poor weather.
It can be mistaken for hawkbit or catsear, but the key difference is its stolons. Hawkbit and catsear do not creep along the ground. The long hairs on the foliage are another strong identifying feature that set mouse-ear hawkweed apart.
Why It’s a Problem
In lawns, mouse-ear hawkweed forms dense mats that smother turf, reducing grass density and leaving dull, uneven patches. Its fine hairs make it unappealing to mow, and it quickly re-establishes from stolons after mowing or partial removal.
It favours low-fertility, compacted, or dry soils, which means it often appears in lawns that are underfed or poorly maintained. If left unchecked, it can take over entire areas of turf, making recovery difficult without renovation.
Management and Prevention
Cultural control methods:
- Improve soil fertility: Regular fertiliser applications strengthen grass growth, helping it outcompete hawkweed.
- Aerate and reduce compaction: Improves drainage and encourages deep root growth of desirable turf species.
- Maintain dense turf cover: Overseed bare patches promptly to limit establishment opportunities.
- Raise mowing height: Taller grass shades out hawkweed seedlings and reduces stolon rooting.
- Water deeply but infrequently: Encourages turf health while discouraging shallow-rooted weeds.
Chemical Control:
Mouse-ear hawkweed is notoriously tolerant to many common lawn herbicides, so chemical control is often limited and slow. However, selective products can help manage infestations as part of an integrated plan.
Recommended herbicide options include:
- Triclopyr/picloram mixtures (NZLA Gold): Provide partial suppression and are among the most effective selective options available in turf.
- 2,4-D/dicamba mixtures (Banvine, Turf Control): Can reduce growth and slow spread when used during active growth periods.
- Clopyralid (NZLA BWC): May offer limited suppression but is not fully reliable on established plants.
Spot-spraying may be more effective than blanket applications. For heavy infestations, glyphosate can be used to remove the weed entirely before reseeding or resodding the affected area.
As with all stolon-forming weeds, repeat treatments and improved turf health are key to long-term control.