Where dune fungi hide in autumn

Sand dunes can look like the least fungal places in Britain. Wind moves the surface, the soil is thin, and by late summer everything seems brittle and grey. Then the rain arrives. From roughly mid-September through to the end of November, fixed dunes, dune grassland and mossy slacks produce a fungal flora that is quiet, specialised and genuinely worth a slow walk.

The trigger is a proper wet spell after dry weather, with mild nights. A day or two after heavy rain, when daytime temperatures sit around 8–14°C, is usually peak. Go early. Fungi on dunes shrivel fast in wind and sun, so a morning visit after overnight rain will show you two or three times as much as an afternoon one.

Reading the ground: marram, fixed dune and slack

Dunes settle into zones, and each supports different fungi. Learning to read them saves a lot of aimless wandering.

• Yellow and shifting dunes: the mobile sand held by marram grass. Few fruiting bodies, but a few specialists push through, often half-buried.
• Fixed dune grassland: closed turf, short herbs, lichen and moss. This is where the colourful, grassland-type fungi appear, often in patches so rich they look scattered rather than grown.
• Dune slacks: the damp hollows, with creeping willow, rushes and thick carpets of moss. By far the most productive and the easiest to damage.

Look at edges rather than centres: the boundary between turf and bare sand, the sides of rabbit runs, old fence lines, south-facing slopes that warm first, and any patch of moss with a few pale gaps in it. Fungi often fruit in loose rings or lines that follow buried roots, so when you find one, scan in a slow arc before moving on.

Partnerships: what the plants get in return

Much of the partnership work on a dune is invisible. Marram grass and other dune plants depend heavily on arbuscular mycorrhizal fungi, microscopic fungi whose threads spread through sand and effectively extend the plant's root system. In nutrient-poor sand, they are how the grass gets enough phosphorus and water to bind the dune together at all. You will never see these as mushrooms; their work shows up as healthy, vigorous marram.

The visible partnerships tend to happen further inland, along the scrubby landward edge. There, birch, willow, pine and sometimes oak form ectomycorrhizal relationships with fungi whose fruiting bodies we actually notice — the ones that appear in lines and rings around a tree and dissolve back into the soil within a fortnight. In the open grassland, waxcaps, corals and clubs are the eye-catchers: small, waxy, often vivid, slow to appear and slow to return if the turf is disturbed. Their exact relationships are still argued over, which is part of why they are so interesting to record.

Recyclers: the fungi clearing what the wind buries

Other dune fungi are simply there to break things down, and dunes bury a great deal: marram litter, thatch, driftwood, seaweed, rabbit droppings, dead roots. One of the most characteristic is the dune brittlestem, which grows on shifting sand among marram and fruits just at the point where buried grass litter begins to rot.

Elsewhere, hunting the recyclers is a matter of looking for disturbance. Turn your attention to:

• Buried wood at the top of the beach and along slack edges, where a dark, damp line of sand sits over timber.
• Old, flattened thatch where sand has drifted over grass.
• Seaweed and rubbish caught in the marram, which supports its own brief flush of fungi.
• Dead branches of burnet rose and creeping willow, often colonised by small, tough species.

These are the fungi doing the unglamorous work of turning sand-buried matter back into nutrients. Without them, the dune would keep its accumulation of dead material and the grassland above would quietly starve.

Beachcombing with fungi in mind

The habits that make for good beachcombing serve fungi well: patience, a hand lens, and a willingness to kneel down. Take a hand lens or small magnifier, a notebook and pencil, a knee mat or a folded bin bag, and something to shield the camera from wind-blown sand. Photograph the fungus where it grows, including a shot of the underside and one of the surrounding turf, before disturbing anything.

A few practical rules keep both you and the dune in good shape.

• Disturb as little as possible. Slacks are fragile; a few footprints through moss can last for years. Keep to existing paths and dune-top tracks.
• Check site designations. Much of the coast is protected, and on Sites of Special Scientific Interest, picking fungi is generally not permitted — even for personal use. On unprotected ground, take only what you can confidently identify and only what you need.
• Never eat from a dune. Identification errors are easy in blown sand and the consequences are serious. Enjoy the looking.
• Watch for livestock and adders on grazed or scrubby dunes, and keep dogs close.

Autumn visits worth repeating

Dune fungi reward going back to the same strip of coast year after year. Note the date, the weather of the preceding week, the zone, and roughly how many of each species you saw, then send the records to your county fungus recording group. Records from coastal sites are genuinely thin, so a careful amateur can add real value.

Walk slowly, look low, and accept that many visits will give you little. The quiet beauty of this corner of coastal nature is partly that it does not announce itself — a few waxy caps in the grass, a line of small brown fruiting bodies along the edge of a rabbit run, and the knowledge that, under the sand, the real work is going on unseen.