Oyster mushroom UK guide: the wild oysters of Britain and how to tell them apart

Wild oyster mushrooms in the UK: where they grow

Wild oyster mushrooms grow throughout Britain on dead and dying broadleaf trees, especially beech and oak. They are fairly common, though they tend to turn up in some woods year after year and be missing from others.

Look for shelves of overlapping caps on standing dead trunks, beech stumps, fallen logs and big broken branches. They often sit well above head height, so it pays to look up as well as down.

They are not a rare treat. Our records for Great Britain hold several thousand finds, which makes the oyster one of the easier wild mushrooms to meet on a winter or autumn walk.

When is oyster mushroom season in the UK?

Oyster mushroom season in the UK runs from summer to early winter, and most British records fall in that stretch. That is also how First Nature describes it for Britain.

Some foragers find them even later. Wild Food UK says they can appear at any time of year and are more common in the winter months.

If you find a pale oyster-like mushroom in warm weather, it may be the pale oyster instead. That relative is mainly a mushroom of the warmer months.

Grey oyster mushroom: the common wild one

The grey oyster mushroom is simply the oyster mushroom, Pleurotus ostreatus, the species you are most likely to find in British woods. Its caps can be grey, brown, cream or almost white, and some young ones look blue-grey.

The caps are fan or shell shaped, usually 5 to 18 cm across. Underneath, white gills run down onto a very short, off-centre stem, and some caps have no stem at all.

It has an odd habit too. Its gills can trap and feed on tiny nematode worms living in the wood. For the full description, see our oyster mushroom card.

Oyster mushroom identification: the checks that matter

To identify an oyster mushroom, check four things together: it grows on wood, the caps are bigger than about 4 cm, the white gills run down the stem, and the spore print is white to pale lilac-grey.

Wood matters most. Oysters grow on trees, stumps and logs, not from soil. If you find something oyster-like in grass, it is a different mushroom.

Size rules out the little oysterlings, which never get beyond about 4 cm. A spore print rules out more. Leave a cap gills down on dark paper for a few hours, and look for that faint lilac tint.

If even one check does not fit, leave the mushroom where it is. A missing feature does not mean a mushroom is safe.

Other wild oysters in Britain

Besides the common oyster, Britain has a few close relatives. They are worth knowing, mostly so you do not mix them up.

The pale oyster (Pleurotus pulmonarius) is paler and lighter in build, and it fruits mainly in warm weather on beech and other broadleaf wood. It can cross with the oyster mushroom, so in-between mushrooms do turn up.

The branched oyster (Pleurotus cornucopiae) has funnel-shaped caps that branch from a shared stem. It grows on rotting broadleaf wood, often elm or beech, in summer and autumn.

The veiled oyster (Pleurotus dryinus) has a frosted-looking cap and a short-lived ring on the stem. It grows on dead beech, oak and horse chestnut from late summer into autumn, and it is scarce.

The olive oysterling (Sarcomyxa serotina) is a late one, appearing in autumn and winter. Its cap is olive green and slimy when wet. First Nature advises against tasting it, as it is thought to contain carcinogens, so treat it as one to leave.

Oyster mushroom lookalikes: what else grows on wood

The main oyster mushroom look alike in Britain is angel's wings, and the others are small oysterlings. Each one fails at least one of the checks above.

Oysterlings such as the peeling oysterling (Crepidotus mollis) are common on dead broadleaf wood. Their caps are 1.5 to 5 cm, soft and jelly-like on top, and their spore print is snuff brown, not lilac. They may be poisonous.

The bitter oysterling (Panellus stipticus), sometimes searched for as the bitter oyster, is smaller still, 0.5 to 3 cm, with a tan woolly cap. It grows in tufts on fallen trunks, often oak, and is known for its very bitter flesh. It is not a food mushroom.

Oyster mushroom vs angel's wings

Angel's wings (Pleurocybella porrigens) is pure white, thin-fleshed and stemless, and it grows on dead conifer wood, while the oyster mushroom is thicker, has a short stem and grows on broadleaf trees.

Treat angel's wings as deadly poisonous. In Japan in 2004, people with kidney failure on dialysis fell ill with a serious brain illness after eating it, and there have been deaths. The exact cause is still not clear.

In Britain it is found mainly in Scotland and northern England, from late summer to late autumn. It often sits on old, mossy conifer stumps and logs. Its cap is like a funnel split down one side, and its spore print is pure white.

So if your mushroom is all white, thin as paper, and on pine or spruce, do not pick it. Oysters on beech or oak with a lilac-tinted print are a different matter.

King oyster mushroom UK: shop-bought oysters explained

King oyster mushrooms sold in the UK are grown indoors, not foraged. The king oyster (Pleurotus eryngii) lives wild in warm grassland from the Atlantic through the Mediterranean, on the roots of plants in the carrot family, and Britain has just one wild record of it.

Pink oyster mushrooms are another species, Pleurotus djamor, from tropical and subtropical regions. There are no wild records of it in Britain, so a pink oyster here has always been grown.

Golden or yellow oysters (Pleurotus citrinopileatus) come from eastern Russia, northern China and Japan. A handful of British records exist, almost certainly escapes from cultivation.

Blue, blue-grey and white oyster mushrooms in shops are usually forms of the ordinary oyster mushroom, Pleurotus ostreatus. That species is also grown on a large scale, which is why it is on supermarket shelves all year.

Picking wild oysters: the law and a safety note

The rules for picking wild mushrooms in the UK depend on where you are and who owns the land. Our article Foraging ethics and the law explains what is allowed.

Only eat an oyster you are completely sure of. If someone feels unwell after eating a wild mushroom, call 999 and keep a piece of the mushroom to show the doctors.