How fast does a mushroom grow, and how long does it live?

“How did this mushroom grow overnight?” — wonders everyone who finds a porcini in the morning where there was nothing the evening before. In fact, mushrooms grow by clear rules, just faster than we're used to with plants. Let's go over the essentials: how many days a mushroom takes to grow, when to expect it after rain, how long it lives, and why the mycelium lives far longer than the mushroom itself.

The mushroom and the mycelium — two very different lifespans

What we pick and put in our basket is only the fruiting body. The fungus needs it to spread its spores, just as an apple tree blooms and bears fruit for the sake of its seeds. The organism itself — the mycelium (fungal network) — hides in the soil or wood and stretches for meters all around.

That's why a mushroom has, in a sense, two different “ages”: the short life of the fruiting body (days) and the long life of the mycelium (years, sometimes decades).

How many days does a mushroom take to grow

Most edible forest mushrooms go from a tiny primordium to full size in 3–9 days, depending on the species and the weather:

• fast, thin-fleshed ones — slippery jacks, honey fungus, birch boletes — manage it in 3–5 days;
• dense, meaty ones — porcini, bay bolete — grow for 6–9 days;
• the chanterelle sits in the middle and lasts longer than the others.

How many days after rain do mushrooms appear

Rain kick-starts growth, but not instantly. The mycelium needs time to “switch on” and grow a fruiting body. On average, the first mushrooms appear 5–7 days after a good warm rain, and the main flush comes on days 7–10. Fast species can manage in 3–4 days. More in our article on when to go foraging after rain.

How many hours does a mushroom grow, and does it grow at night

A mushroom doesn't grow in a few hours — that's a myth. But a full day brings noticeable growth: a young mushroom adds about 1–2 cm in height per day, and grows most actively at night, in the cool and damp. That's why it seems a mushroom “shot up overnight.” Why this really happens, we explain in the article do mushrooms grow by day or at night.

How long does a mushroom live

The fruiting body doesn't live long — mostly 5–14 days. At first the mushroom is young and clean, then the cap gets tougher, the underside darkens and larvae appear. The picking “window” is narrow: be a few days late and you'll find an overgrown, maggoty mushroom. Why you shouldn't pick those — see the article why you shouldn't pick old and maggoty mushrooms.

How long does the mycelium live

The mycelium, on the other hand, lives a long time — for years and decades. It survives winter, drought and frost in a dormant state, and when moisture and warmth return, it sends up mushrooms again. That's why mushroom spots are so reliable: found a glade full of porcini? Come back there next year too.

That's also why it doesn't harm the mycelium whether you cut the mushroom or twist it out. What does harm it is something else — digging up the forest litter. We wrote about this in the article how to pick mushrooms: cut or twist.

What growth speed depends on

• Warmth. Growth is fastest at +15…+20 °C and slows down in the cold.
• Moisture. After rain and in foggy weather mushrooms grow actively; in drought they stall.
• Species. Thin-fleshed mushrooms hurry, meaty ones grow more slowly but last longer.
• Age of the mycelium. A mature mycelium produces mushrooms more abundantly.

Sources

• “Identification Guide to the Fungi of Ukraine” (Kyiv, Naukova Dumka publishing house).
• Fungi in GBIF, the global biodiversity database.
• Mushroom on Wikipedia.