About the Grotto

February 17, 2008

This information about the Grotto was published in the Auckland Regional Council Big Clean Up newsletter in December 2007.

The Jewel in Onehunga’s Crown

It’s affectionately known to locals as ‘the grotto’: a green hectare of land in Onehunga formed when a lava lake from the Mt Smart eruption collapsed.

The site, which looks like a crater with volcanic rock sides, was once occupied by Onehunga Laboratories Limited, which used the diatomaceous earth to manufacture mild abrasives called ‘Grotto Maid’ and ‘Denture Glow’.

During the Second World War the crater was also used to grow crops of tobacco and to house and breed Peking ducks.

Back in 1973 the grotto was bought by a local man. His motivation for the purchase came from something his own father used to say about owning his own land. “Son, see that hill? That is my hill,” his father used to tell him. So as the Onehunga man’s own children grew up, he was able to say: “See that hole? That is my hole.” The grotto remained in private ownership until 2006 when Auckland City Council identified the area as of ecological and geological significance, worth protecting in perpetuity. The council purchased the grotto for a public park.As land values rise and the size of the average Auckland section shrinks, local parks are becoming more and more important to communities as places to meet others, walk the dog or just sit and forget about the busy world. The grotto will be an extra special park. During the winter it acts as a wetland during periods of rainfall and is visited regularly by pukeko, mallard ducks, kingfisher and herons.  Other visitors include fantail, tui and the ubiquitous waxeye.Martin compiled a list of flora in the Grotto from July 2002 – November 2003 and identified it as “a local botanical treasure”.  You can read the article below:

The crater also contains a very rare NZ carex, or grass. Plans are underway to remove all the invasive exotic plant species and replant with suitable natives.

There is strong community interest and the beginnings of a local community group are already underway. If you are interested in being part of it please email jamesandmeredith@xtra.co.nz

The Grotto was also featured in Volume 58 (2) December 2003 edition of the Auckland Botanical Society Journal.

An article on “The Flora of “The Grotto”: a volcanic collapse pit on the lower slopes of Onehunga, Auckland” was written by Timothy J Martin.


The Flora of “The Grotto”: a volcanic collapse pit on the lower slopes of Onehunga, Auckland