Limestone Endemic Giant Daisies and Plenty of Sticks
Mangarākau swamp was initially brought to my attention by Geoff Davidson in the summer of 2017, he was instrumental in protecting the swamp with the Native Forest Restoration Trust. Subsequently, the largest gathering of my extended family was planned across the road for that Christmas. Mangarākau is the largest remaining wetland in the Nelson region, nearly as large as all other freshwater swamps in the region combined. Draining the swamp has proved futile for a 150 years, in part due to an enormous granite boulder that blocks attempts to drain it into the Whanganui Inlet.
Commanding limestone cliffs rise sharply from the edge of the swamp. These are clothed in rātā (Metrosideros robusta), which is best viewed in December when the scarlet stamens burst from these forest giants. Ascending a steep track from the base of the cliff, we pass tangles of kiekie (Freycinetia banksii) and a carpet of kidney fern. Emerging into a grassy scrubland below the base of these spires, I was struck by a healthy population of the limestone endemic Brachyglottis hectorii. The position owing to its wind dispersal mechanism. Carried by the wind, the seed drops here as it breaks against the cliff face. It is an attractive shrub in Asteraceae or daisy family, capable of heights to 4m with jagged toothed leaf margins. It shares cottony, tomentose leaves with bushman’s toilet paper (Brachyglottis repanda); a tramping and coronavirus desperation measure.
Mangarākau translates to ‘plenty of sticks; a great many trees’, probably reflecting the large mānuka scrublands, a species very useful as tinder for fires. The trees present around the swamp would have largely been wet-tolerant pukatea (Laurelia novae-zelandiae) and kahikatea (Dacrycarpus dacrydioides). Drier areas facilitate the growth of mānuka and Gleichenia dicarpa fernland. Four lakes are surrounded by a shifting gradient of raupō (Typha orientalis), Machaerina arthrophylla and Lepidosperma australe sedge. The plant distributions are influenced by the acidity and chemistry of differing nutrient inputs. These from two distinct geological zones that border the swamp, one of granite to the east and the other limestone in the west.
