survives on the windy offshore islands
- Size
- Height: 20–50 cm
- Lifespan
- 3–5 years
- Diet
- Photosynthetic. Draws energy from sunlight. Obtains nutrients from coastal soils enriched with guano.
- Habitat
- Coastal cliffs, rocky shores, seabird colonies and offshore islands. Prefers exposed, windy sites with salt spray. Often grows near seabird nesting colonies.
- Range
- Coastal areas of North and South Islands. Once widespread now restricted to offshore islands and few mainland sites. Most common on predator-free islands.
- Endemism
- Endemic
- Main Threats
- Habitat loss from coastal development is primary threat. Predation by introduced mammals. Competition from invasive weeds. Climate change affecting coastal habitats.
- Population
- Populations declined dramatically. Listed as Nationally Critical by NZPCN. Restricted to predator-free offshore islands and few protected mainland sites.
- Conservation Status
- Nationally Critical
- Human Risk
- harmless
- Handling Note
- native herb, edible leaves safe to handle
- Conservation Note
- Endemic herb; restricted to specific coastal sites and threatened by habitat loss and grazing.
- Assessment
- NZTCS Vascular Plants (2023)
- Te Ao Māori
- In Māori tradition nau was important green vegetable gathered from coastal areas. Leaves eaten fresh or cooked. Sharp, peppery flavour appreciated. Plant also used medicinally. Decline of nau is great loss. Conservation efforts working to bring it back to mainland. Taonga or treasure of coast. Plant once common now rare. Reminder of what lost and what trying to save.
Rats eat it relentlessly. Lepidium oleraceum is critically endangered coastal herb. Plant that was pushed to edge. Once common on mainland coastlines. Decimated by introduced mammals and habitat loss. Leaves have sharp, peppery flavour similar to watercress. Now found mainly on offshore islands where predators are absent. Plant that survives only where rats cannot reach.
Plant has fleshy, lobed leaves. Bright green and glossy. Small, white flowers arranged in dense clusters at tips of branches. Appear in spring and summer. Followed by small, flat pods containing seeds.
Decline of native cress is story of multiple pressures. Rats and rabbits eat leaves and stems. Preventing regeneration. Coastal development destroys habitat. Invasive weeds compete for light and space. Plant now extinct on mainland. Surviving only on offshore islands where predators eliminated or never arrived.
Conservation efforts underway to restore mainland populations. Seeds collected from island populations. Stored in seed banks. Plants grown in nurseries. Reintroduced to predator-fenced sanctuaries. Some reintroductions successful. Plants flowering and setting seed.
To see native cress is to take boat to offshore island. Island is remote. Cress grows on wind-blown cliffs. Bright green and glossy. Small white flowers nodding. Rats are not here. Plant is safe. Does not know it is endangered. Does not know it was pushed to edge.
It just wants to grow. Still hoping to return to mainland. No one told it otherwise.