buellia crust lichen spreading in grey patches on bare rock
- Size
- Width: 2–10 cm
- Lifespan
- 10–50 years
- Diet
- Grows on bark of trees, rocks, and wood in open, sunny locations. Requires clean air, stable bark or rock surfaces, and good light. Tolerates sun, wind, and moderate drought. Prefers open, exposed sites with stable surfaces and minimal disturbance.
- Habitat
- Grows on the bark of trees, on rocks, and on wood throughout New Zealand. A creature of the bark and the stone, the branch and the boulder. Found from sea level to the montane zone, particularly in open, sunny locations where the surface is dry and the air is clean. The lichen of the dark disc, the one that scatters across pale surfaces like quiet punctuation.
- Range
- Found throughout the North and South Islands on bark of trees, rocks, and wood. Most common in open, sunny locations on native and introduced trees. Also found in temperate regions worldwide.
- Endemism
- Native
- Main Threats
- None significant. This species is common and widespread in open, sunny locations. Localised threats include forest clearance, removal of old trees, and air pollution. Classified as Not Threatened, with healthy populations on bark of native and introduced trees throughout New Zealand.
- Population
- Not Threatened. Buellia crust lichen is common and widespread in New Zealand, particularly on the bark of native and introduced trees in open, sunny locations. It also grows on rocks and wood.
- Conservation Status
- Not Threatened
The one that looks like a full stop at the end of a sentence has a body that is a thin, crusty layer that grows on the surface of the bark or rock, forming a pale grey or brownish patch. But the most distinctive feature is the dark, black discs that cover the surface. These discs (apothecia) are scattered across the pale background like dots on a page, like quiet punctuation at the end of a thought. It is the lichen of the dark disc, the one that looks like the forest is writing a very long sentence.
What makes it special is the contrast. Buellia crust lichen is one of the most punctuation-like lichens in New Zealand. Its pale grey or brownish crust provides a quiet background for the dark, black discs. The discs are small, usually less than a millimetre across, but they stand out clearly against the pale surface. They are scattered irregularly or sometimes clustered, creating a pattern that looks like writing or a map of the stars. It is the lichen of the quiet mark, the one that adds punctuation to the bark, the one that makes you lean in to read the message.
The buellia crust lichen is a crustose lichen, meaning it grows flat on the bark or rock, like a crust of paint, rather than upright or leafy. Its body is a smooth or slightly cracked crust, often forming irregular patches. The apothecia are black, round, and often have a raised rim, like tiny volcanoes. Under a hand lens, the apothecia are beautiful, perfect circles with a textured surface.
Biologically, the buellia crust lichen is a partnership, a fungus and an alga living 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 buellia crust lichen is to find the dark dots on the pale bark. It is pale, crusty, and dotted, a living punctuation mark on the tree. You can run your finger over the surface and feel the tiny, raised discs. It is the lichen of the dark disc, the one that scatters across pale surfaces like quiet punctuation, the one that proves that the forest has its own language.