Here's a retaining wall of cemented boulders just by the Esplanade. The renovations to this part of St Clair are not very old, perhaps 5 or 6 years.
It puts into question the old tale about lichens taking a long time to grow. Some indeed do. Apparently Rhizocarpon geographicum a lichen found all over the world, which favours growing on rocks in alpine and polar regions, grows at between 3mm and 25mm per year.
This species (which according to a now out-of-print book) is Xanthoria parietina is clearly not that slow growing! There are several varieties, some of which grow on smooth-barked trees. But the preferred habitat is coastal rocks beyond the reach of the tide and spray.
Colour varies according to how much sunshine the colony is exposed to. And photographs in a more recent book, show a grey variant with only a hint of yellow. This book also reports, wouldn't you just know it, that the New Zealand lichen flora is very rich. I should say, I stayed away from the very impressive two volume 'proper' lichen book - David Galloway's Flora of New Zealand : lichens : including lichen-forming and lichenicolous fungi published in 2007 - far too complicated for me!
The out-of-print book was Lichens of New Zealand by William Martin and John Child. 1972. AH & AW Reed; and the recent book was New Zealand lichens by Bill and Nancy Malcolm. 2000. MicroOptics Press. (a home-made publication if ever there was - but useful nontheless). Incidentally the University catalogue tells me Martin was born in 1886, and as there is not death date, and as the book was a first edition I assume that he would have been still growing slowly in 1972. He can't surely be alive now though!
