native cress of stream banks and wet forest margins
- Size
- Height: 20–50 cm
- Lifespan
- 3–5 years
- Diet
- Not applicable (herb). Photosynthetic.
- Habitat
- Coastal cliffs, rocky shores, seabird colonies and offshore islands. Prefers exposed, windy sites with salt spray. Often grows near seabird nesting colonies where the soil is enriched with guano.
- Range
- Coastal areas of the North and South Islands. Once widespread, now restricted to offshore islands and a few mainland sites. Most common on predator-free islands.
- Endemism
- Endemic
- Main Threats
- Habitat loss from coastal development is the primary threat. Predation by introduced mammals (rats, rabbits). Competition from invasive weeds. Climate change affecting coastal habitats.
- Population
- Populations have declined dramatically. The species is listed as Nationally Critical by NZPCN. It is now restricted to predator-free offshore islands and a few protected mainland sites. Conservation includes predator control, habitat restoration and ex situ seed banking.
- Conservation Status
- Nationally Critical
A critically endangered coastal herb. A plant that was pushed to the edge.
It was once common on mainland coastlines. It has been decimated by introduced mammals and habitat loss. The leaves have a sharp, peppery flavour similar to watercress. It is now found mainly on offshore islands where predators are absent. A plant that survives only where the rats cannot reach.
The plant has fleshy, lobed leaves that are bright green and glossy. The small, white flowers are arranged in dense clusters at the tips of the branches. The flowers appear in spring and summer, followed by small, flat pods containing the seeds.
The decline of native cress is a story of multiple pressures. Rats and rabbits eat the leaves and stems, preventing regeneration. Coastal development destroys its habitat. Invasive weeds compete for light and space. The plant is now extinct on the mainland, surviving only on offshore islands where predators have been eliminated or never arrived.
Conservation efforts are underway to restore mainland populations. Seeds are collected from island populations and stored in seed banks. Plants are grown in nurseries and reintroduced to predator-fenced sanctuaries. Some of these reintroductions have been successful, with plants flowering and setting seed.
To see native cress is to take a boat to an offshore island. The island is remote. The cress grows on the wind-blown cliffs, bright green and glossy, small white flowers nodding. The rats are not here. The plant is safe. It does not know it is endangered. It does not know it was pushed to the edge.
It just wants to grow. It is still hoping to return to the mainland.