There are two main rushes in the estuary. The most common is wīwī, the sea rush, Juncus maritimus variety australiensis, which is the southern form of a world-wide species. The Māori name relates to the wind rippling across the surface.
It grows in dense masses and is not palatable, therefore it has survived unscathed since farming began. It can tolerate inundation by salt water, intercept driftwood and is very important in making the estuary secure, both physically and as a habitat for marine life and birds.
Around the edges of the estuary and along water channels the jointed wire rush is most common, named oioi by Māori and botanically as Leptocarpus similis, with most of its relatives growing in Australia. Oioi spreads using long stems under the mud and creates uniform swards rather than clumps, therefore attracting different sea life like small fishes, including whitebait. Several other rushes grow in the estuary, recognizable by different colour, location and shape, and sometimes an attractive sand tussock grass (Poa billardierei) grows around the sandy edges.