The New Zealand Plant Conservation Network

We live in Taranaki and are digging a pond in our front garden. Having tasted some Chinese water chestnut, we thought we might try to grow some in our pond. So we googled it and found http://rfcarchives.org.au/Next/Fruits/WaterChestnut/GrowingWChestnuts9-96.htm where it says it could threatened a rare native sedge "Maori chestnut". Can you tell me which native species it might be referring to, is it edible, and if we should try and grow some of that instead of the exotic one?

It's a good thing you checked up on the Chinese water chestnut Eleocharis dulcis. It was listed in the unwanted organisms register in 1996 (http://www1.maf.govt.nz/uor/searchframe.htm) and it's cultivation is prohibited in New Zealand due to its invasive nature. There is a significant number of native wetland species which are already classified as threatened and at risk.
I have had look through a range of online databases for an entity with the common name 'Maori chestnut' and not been able to find anything and without a scientific name it will be difficult to go much further. All the native species of Eleocharis are tiny and I know of no food use they have. If you are interested in growing native plants for their food value I suggest you explore this database here which includes a large quantity of information about traditional Maori uses for native plants. http://www.landcareresearch.co.nz/resources/data/nga-tipu-whakaoranga-maori-plant-use-database
Sorry I can't be more help

Hi Catherine,
Yea you definitely don't want to be growing Chinese water-chestnut in New Zealand as it is a highly invasive species.
One native wetland plant you could try is Raupo (Typha orientalis). It was one food source utilised by Maori at certain times of the year. It has fat juicy rhizomes (roots) that can be eaten, which are high in starch and sugar. Its young leaves can also be eaten, and the flower spikes produce large quantities of pollen which can be used as a highly nutritious food source too.
I think this plant is also a very attractive, so even if you don't eat it you can enjoy it as an ornamental.

Have fun with the pond.

Cheers,
Rowan

Thanks Jesse & Rowan, I appreciate your cautious advice and various links which are interesting. The bull rush does look great and I've seen quite a lot of it in Australia. It might be too large and aggressive for our little pond though. Our pond is not connected to any natural wetland system, so I don't know if there's much chance of our water chestnut (if we have any) invading them? What're its main means of invasion? Is it the careless discard of rhizomes or?

Just a thought - "Maori Chestnut" may possibly refer to the Cook Island Maori Chestnut (Inocarpus fagifer, Fabaceae) which is also known as Polynesian Chestnut - it has nothing to do with Eleocharis - but none of the New Zealand Eleocharis species produce a "bulb" so its hard to see how that name could be applied to them. However, kutakuta (Eleocharis spacelata) had traditional uses as a weaving plant - so possibly someone made a very bad connection in vernaculars with these two (very different) Eleocharis.