Shepherd’s Purse (Capsella bursa-pastoris)
Shepherd’s purse is a small, fast-growing annual weed that can germinate almost any time of the year. It’s commonly found in lawns, gardens, and bare soil throughout New Zealand. Although not especially competitive against well-established turf, it quickly colonises thin or patchy areas and can become unsightly in home lawns.
It thrives in cool, moist conditions and is most noticeable in winter and early spring when lawn growth slows. Because it can produce several generations in a single year and its seed remains viable for decades, it often reappears even after successful control.
Identification
Shepherd’s purse begins as a small rosette with irregularly lobed leaves that vary greatly in shape. The leaves are sometimes mistaken for hawksbeard or Cape weed, but they are smaller and less hairy underneath.
As the plant matures, it sends up thin flowering stems 20–30 cm tall, each topped with clusters of tiny white flowers. Once flowering finishes, distinctive heart-shaped seed pods develop — a key identifying feature that gives the plant its name.
Each plant can produce thousands of seeds that fall close to the parent, allowing dense colonies to form in lawns, paths, and garden edges.
Why It’s a Problem
Shepherd’s purse competes with grass seedlings in newly sown lawns and can form clumps that disrupt the smooth surface of established turf. It thrives in compacted, low-fertility soils where grass growth is weak, often taking advantage of damp conditions and open patches.
Because it grows and sets seed so quickly, even small plants can contribute to a large soil seed bank, leading to persistent infestations if left unchecked.
Management and Prevention
Shepherd’s purse is best controlled through consistent lawn care practices that maintain density and prevent seed germination.
Cultural control methods:
- Encourage dense turf: Overseed bare or thin patches in autumn or spring to prevent light from reaching the soil surface.
- Regular mowing: Frequent mowing prevents plants from flowering and setting seed.
- Improve soil health: Apply balanced fertiliser to promote grass growth and reduce open space.
- Aerate and topdress: Improve drainage and reduce compaction, as compacted soil favours germination.
- Remove plants early: Hand-weed small infestations before seed pods form to prevent reinfestation.
Chemical Control
Shepherd’s purse is tolerant of several selective herbicides, so early treatment is important. Young plants are much easier to kill than mature, flowering ones.
Effective herbicides include:
- MCPA and 2,4-D – highly effective for control in turf and broadleaf weed mixes.
- Triclopyr/picloram mixtures (NZLA Gold)
- Glyphosate – effective for spot-spraying in non-selective situations but will damage grass.
Apply when the weed is actively growing and repeat if new seedlings emerge. Consistent lawn management will prevent long-term re-establishment from the seed bank.