buttons up the exposed sunny rock faces

Size
Width: 2–15 cm
Lifespan
20–100 years
Diet
Obtains nutrients via symbiotic partnership. Fungus provides structure. Alga provides photosynthetic food. Requires clean air and good light.
Habitat
Grows on rocks and boulders throughout New Zealand, particularly in exposed, sunny locations. A creature of the bare stone, the weathered rock, the places where the surface is hard and the sun is bright. Found from sea level to the alpine zone, on native and introduced rock types. The lichen of the smooth crust, the one with neat, rounded fruiting discs like tiny buttons.
Range
Found throughout the North and South Islands on rocks and boulders in exposed, sunny locations. Most common in the South Island's high country and the North Island's volcanic plateau. Also found in temperate and cold regions worldwide.
Endemism
Native
Main Threats
None significant. This species is common and widespread on rocks in exposed locations. Localised threats include quarrying of rock outcrops, air pollution, and climate change affecting rock surface conditions.
Population
Not Threatened. Porpidia lichen is common and widespread in New Zealand, particularly on rocks in exposed, sunny locations. It grows on native rock types, often on boulders and rocky outcrops.
Conservation Status
Not Threatened
Human Risk
harmless
Handling Note
crustose lichen, safe to handle
Conservation Note
Native lichen; not assessed by NZTCS as lichens are generally outside the scope of current threat classifications.
Te Ao Māori
No recorded Māori name distinguishes the porpidia lichen from other lichens. Lichens were generally called pūkohu (mosses and lichens) or pukorokoro (crustose lichens). The neat, button-like dots on the rock would have been noticed. They looked like the eyes of a fish. Like the spots on a bird. But no distinct name survives. The porpidia lichen was sometimes used as a dye. The pale pigment could be extracted. It was used to colour fibres. Though it was not as vibrant as other lichens.
Without it, the rock is just stone. With it, there are buttons. Porpidia lichen looks like it has been organised by a tidy mind. It has a body that is a smooth, crusty layer. It grows on the surface of the rock. Forming a pale grey to off-white patch. The crust is even and unbroken. Like a coat of smooth paint. Scattered across the surface are neat, rounded, black fruiting discs (apothecia). Arranged like tiny buttons on a pale fabric. It is the lichen of the neat surface. The one that likes things tidy. The one that makes the rock look like it has been decorated. What makes it special is the neatness. Porpidia lichen is one of the tidiest lichens in New Zealand. Its crust is smooth and even. Not cracked or wrinkled like many other crustose lichens. Its fruiting discs are round and regular. With a neat, raised rim. They are scattered across the surface in a way that looks almost deliberate. Almost designed. It is the lichen of the tidy mind. The one that cannot stand mess. The one that proves that even the oldest things can be organised. The porpidia lichen is a crustose lichen. It grows flat on the rock. Like a crust of paint. Rather than upright or leafy. Its body is a smooth, continuous crust. Often forming circular patches or irregular stains. The apothecia are black, round, and often have a raised, pale rim. They are usually flat or slightly convex. Like tiny buttons. Under a hand lens, the apothecia are beautiful. Perfect circles with a textured surface. Biologically, the porpidia lichen is a partnership. A fungus and an alga live together. The fungus provides structure and protection. The alga provides food through photosynthesis. The apothecia are the spore-producing structures. Releasing spores into the air. To find porpidia lichen is to find the neat, dotted patch on the rock. It is pale, smooth, and tidy. A living button collection on the stone. You can run your finger over the smooth crust. Feel the neat, raised discs. It is the lichen of the smooth crust. The one with neat, rounded fruiting discs like tiny buttons. The one that proves that even the oldest things can be beautiful.