Oyster Mushroom

Edible

Scientific name	Pleurotus ostreatus
Family	Pleurotaceae
Portuguese name	Repolga, Cogumelo-ostra, Pleuroto-ostra
English name	Oyster mushroom
Season	October, November, December, January, February, March
Habitat	Oak forest, Eucalyptus, Mixed forest

Description

Pleurotus ostreatus (oyster mushroom) is one of the most common, accessible and recognisable mushrooms in the world. It grows on dead and weakened wood in characteristic shelf-like tiers. In Portugal it is known as “repolga” — a traditional folk name, as well as “cogumelo-ostra” (oyster mushroom) and “pé-de-botão”.

Cap

• Diameter: 5–25 cm
• Shape: fan-shaped, shell-shaped (hence the name “oyster mushroom”)
• Colour: white to grey, bluish-grey or brown. Darkens in cold weather
• Surface: smooth, slightly velvety
• Margin: thin, inrolled when young, later wavy

Stem

• Height: 1–4 cm (often virtually absent)
• Position: eccentric or lateral — the stem is offset towards the edge of the cap
• Colour: white
• Surface: firm, with velvety down at the base

Flesh

• Colour: white
• Smell: pleasant, mild, with hints of anise
• Taste: mild, delicate
• Texture: firm in young specimens, tough in older ones

Gills

• Colour: white, becoming cream to yellowish with age
• Attachment: strongly decurrent (running far down the stem) — a characteristic feature
• Spacing: moderate

Spore print

White to pale lilac.

Where and when

Season in Portugal

• Main season: October–March
• One of the few mushrooms that fruits during winter
• Actively grows at 5–20°C
• Appears after rains in the cold season

Habitats in Portugal

• Broadleaf trees — the main substrate. Grows on trunks, stumps and branches of:
  • Poplar (Populus)
  • Elm (Ulmus)
  • Beech (Fagus)
  • Oak (Quercus)
• Eucalyptus plantations — can grow on eucalyptus
• Grows in tiers (shelves) — in groups on trunks
• May grow on living but weakened trees (weak parasite)
• Found throughout Portugal

Ecology: a carnivorous mushroom!

The oyster mushroom is one of the few known carnivorous fungi. Its hyphae release a volatile ketone (3-octanone) that paralyses nematodes (microscopic worms). The fungus then digests the paralysed prey, obtaining an additional source of nitrogen.

This is an adaptation to life on wood, which is nitrogen-poor. The discovery was published in Science Advances (2023).

Cultivation in Portugal

The oyster mushroom is one of the most widely cultivated mushrooms in the world and in Portugal:

• Aromas & Boletos (Leiria) — production of spawn, substrates and growing kits
• Golden Cap — cultivation on wheat straw and recycled sawdust
• Agro Cachola — commercial production
• Grown on straw, sawdust, eucalyptus substrate
• Price fresh: approximately 9–18 EUR/kg from Portuguese producers

Look-alikes

The oyster mushroom is one of the safest mushrooms to forage. Serious poisonous look-alikes in Portugal are virtually absent.

Safety rule

Growing on broadleaf wood in tiers, with white decurrent gills and a white to lilac spore print — it is an oyster mushroom. On coniferous trees — exercise more caution.

Culinary use

The oyster mushroom is a versatile culinary mushroom with a tender texture.

Preparation methods

• Pan-frying — with garlic, onion and olive oil (the most popular method in Portugal)
• Stewing — in cream sauces
• Soups and stews — adds a delicate mushroom flavour
• Breaded — coated in breadcrumbs and fried (Portuguese “repolgas panadas”)
• Pickling — with vinegar and spices

Notes

• Use only caps of young specimens — stems are tough
• Old specimens are tough and flavourless — collect young ones
• Does not require pre-boiling

See Also

Habitats:

• Montado (Cork Oak Woodlands)
• Eucalyptus Plantations
• Mountain Forests

Related articles:

• Seasonal Foraging Calendar
• Mushrooms in Portuguese Cuisine

Sources

1. Naturdata — Pleurotus ostreatus em Portugal
2. Fungipedia Portugal — Pleurotus ostreatus
3. HortoFungi — Nomes populares em Portugal: Pleurotus, Repolgas
4. Lee et al. — A carnivorous mushroom paralyzes and kills nematodes via a volatile ketone // Science Advances, 2023
5. BioDiversity4All / GBIF Portugal — species records
6. Aromas & Boletos (boletosdeorum.pt) — commercial cultivation in Portugal

Disclaimer: Identifying mushrooms from descriptions and photographs on the internet is not a substitute for consulting an experienced mycologist. The authors assume no responsibility for the consequences of collecting and consuming mushrooms.