Clustered Dock (Rumex conglomeratus)
Clustered dock is a deep-rooted perennial weed that often appears in New Zealand lawns, pastures, and waste areas. It’s closely related to broad-leaved dock and shares many of the same characteristics—large leaves, strong taproots, and an ability to regrow after cutting or spraying.
In lawns, clustered dock tends to stay small and low to the ground, forming flat rosettes that survive mowing. In less maintained areas, it grows much larger, sending up tall flowering stems in spring. Once established, it’s difficult to remove completely because of its tough taproot and long-lived seed bank.
This weed thrives in heavy, poorly drained soils and low-lying areas. Its persistence often indicates compacted or under-fertilised soil, and neglecting it can allow it to spread quickly through seed and regrowth from root fragments.
Identification
Clustered dock forms broad, hairless leaves that grow in a rosette from a central crown. The leaves are long and smooth-edged, with a more even width from base to tip than those of broad-leaved dock, which tend to flare out wider near the base.
When mature, clustered dock produces tall, upright stems with clusters of small green flowers that turn red and finally brown as they dry. Each seed is enclosed in a small, three-winged fruit with evenly sized, inflated “bladders,” which helps distinguish it from other dock species.
Underground, a single thick taproot anchors the plant deeply into the soil, allowing it to survive mowing, grazing, or partial removal.
Why It’s a Problem in Lawns
Clustered dock competes with grass for light and nutrients, particularly in damp or compacted soil where grass struggles to grow. The broad leaves shade out finer turf species and can leave large bare patches once they’re removed.
It’s also difficult to control because cutting or partial digging rarely removes the full taproot. The plant can reshoot from any remaining root fragment, and its seeds can remain viable in the soil for years.
While dock is more commonly associated with pastures, it can easily invade lawns in wetter regions or where drainage is poor.
Control in Home Lawns
Like other perennial weeds with deep taproots, clustered dock requires persistence. Physical removal alone often isn’t enough unless you extract the entire root system.
Best control methods:
- Physical removal: Dig out plants using a long weeding knife or spade, removing as much of the taproot as possible. Do this after rain when the soil is soft. Any remaining root piece can regrow, so recheck the area after a few weeks.
- Chemical control: Use a selective herbicide containing triclopyr/picloram (NZLA Gold) for strong control in lawns. It can also be suppressed with clopyralid (NZLA BWC) or dicamba/2,4-D mixes, though multiple applications may be needed for mature plants.
- Non-selective control: In heavily infested areas or lawn renovation projects, spot-treat with glyphosate before reseeding. Avoid applying while the weed is flowering.
- Cultural management: Improve soil drainage and aeration to reduce compacted conditions where docks thrive. Fertilise to strengthen turf density and overseed bare patches to prevent re-infestation.
Prevention Tips
- Aerate lawns yearly to improve drainage and reduce compaction.
- Maintain consistent lawn nutrition to keep grass vigorous and competitive.
- Avoid overwatering or letting water pool in low spots.
- Reseed bare areas quickly after weed removal to prevent dock seedlings from taking hold.
- Dispose of seed heads carefully—dock seeds remain viable in the soil for many years.