Broad-leaved Dock (Rumex obtusifolius)
Broad-leaved dock is one of the more common broadleaf weeds found across New Zealand lawns. It’s a deep-rooted perennial that can quickly take hold in compacted or poorly drained soils, forming large leaves that shade and smother surrounding grass.
Originally more of a pasture weed, dock also shows up in lawns where it adapts by producing smaller, low-growing leaves that sit flat against the ground, just low enough to dodge the mower. Its thick taproot stores energy and allows it to regrow repeatedly even after cutting or spraying, making it a frustrating weed to get rid of once established.
Each plant can produce thousands of seeds, and those seeds stay viable in the soil for many years. That means once you’ve had dock, it can reappear long after you thought it was gone.
Identification
Dock has large, broad leaves that are often wider near the base and taper slightly toward the tip. The leaves are hairless, dark green, and have a distinctive wavy edge.
When it flowers, dock sends up tall stems covered in clusters of small greenish-red seed pods that turn brown as they mature. Underground, it develops a strong, fleshy taproot that can extend well below the surface, often the reason it survives mowing and partial removal.
In lawns, dock can be mistaken for other broadleaf weeds, but its thick taproot and smooth, broad leaves make it easy to identify once you know what to look for.
Why It’s a Problem in Lawns
Dock competes aggressively with grass for light and nutrients. Its broad leaves shade out fine lawn species, leaving thin, bare patches that worsen over time. Because it thrives in damp, compacted, or low-fertility soils, its presence usually points to an underlying lawn health issue.
Once mature, dock can survive mowing and partial herbicide treatments, meaning it often reappears unless properly treated down to the root.
Control in Home Lawns
Dock is difficult to eliminate completely, but a combination of physical and chemical control works best.
Best control methods:
- Manual removal: For small infestations, use a narrow spade or weed puller to dig out the entire root. Leaving even a small section of taproot behind can lead to regrowth.
- Chemical control: Selective broadleaf herbicides containing actives such as triclopyr, picloram, or clopyralid provide the best results in lawns. Products like NZLA Gold are effective when applied while plants are actively growing.
- Glyphosate (spot spraying): In extreme cases or before renovation, glyphosate can be used to spot-treat individual plants. For best results, apply when the plant is young and actively growing, and avoid spraying when seed heads are present.
- Cultural management: Aerate compacted areas, improve drainage, and maintain healthy lawn density through fertilising and overseeding. Docks thrive in weak, compacted soils—fixing those issues helps stop them from returning.
Prevention Tips
- Avoid over-watering and improve soil structure with regular aeration.
- Keep fertility balanced with consistent feeding throughout the growing season.
- Reseed bare patches quickly after weed removal to stop dock seedlings from re-establishing.
- Keep mowing height moderate; a healthy, thick lawn canopy helps crowd out dock seedlings.