This article was published in the Titirangi Tatler, November 2012
Matangaoa - NZ Watercress
Watercress is well-known and enjoyed either as a green salad or lightly steamed to accompany pork and puha. This plant, which clogs slow-flowing streams, is an Asian/European plant.
But Maori and Captain Cook knew the pleasure of eating the native equivalent, Rorippa divaricata or Matangaoa. It is not a stream plant but likes sites of disturbance where it can gain a foothold and grow quickly before longer-lived plants get established.
Once common throughout the country, it is now displaced on the mainland by exotic weeds and is generally found only on off-shore islands. Unlike watercress, it is not a wide-spreading, creeping plant but a rosette-forming, low plant until the flowering stem develops into a one metre tall spike.
The leaves on the flower stem are sparse so the best parts for eating are the basal leaves and it will take several plants to make a salad. Simply pick the freshest leaves, add salt and mayonnaise and enjoy! Their crisp texture and spicy flavor make a great taste on their own, or Rorippa will enhance the meal when mixed with other salad ingredients.
Always let the flowers go to seed to ensure another crop next year. Collect some seed when ripe, i.e. just before the pods dry and split open, flinging the seed quite some distance. Sow again in the spring for a new crop rotation.
Where the ground is disturbed, the naturally sown seed will grow prolifically, but in undisturbed conditions there may be no germination at all.
Rorippa divaricata is an endemic species, growing only in New Zealand. There is a second species that also occurs in Australia. Rorippa laciniata has recently colonized the Hikurangi Swamp in Northland and is now in cultivation at our nursery. It is not a plant of imposing presence, but once you have tasted it, it will be a frequent item on your menu. A straggly, sprawling form hides the foliage under a tangle of flower spikes. Again it is best to pick the young foliage from the base of the plant, even before the flower spike starts to grow.
Enjoy the tangy flavour in a salad or in a cheese and ham sandwich. Delicious.