A bit like a sponge on the kitchen sink,
its green the colour of scum after washing up
or the green of mould on a bread-crust,
the lichen clings to its tree with the tenacity
of verdigris staining a copper pot.
A coarse raincoat full of holes, a shaggy blanket,
damaged plaster coming off the wall,
a five-o'clock shadow, an advanced case of psoriasis.
A fungus and algae sandwich, the lichen grows
slowly but imperturbably, working together fibre in photobiont.
Rock-breaker, cure-provider, air pollution indicator,
pioneer in plant succession, epitome of mutualism,
a universe of purpose and deliberate design
in a rough greenish dishcloth stuck to a tree.