How fast porcini grow, and how long they live

“Yesterday there was nothing, and today there's a porcini the size of a fist” — that's no exaggeration, just ordinary forest magic. Porcini really do grow fast, though not in a matter of hours, as it sometimes seems. Let's be honest about it: how many days they take to grow, how long after rain to expect them, and how long a single fruiting body actually lives.

How many days does a porcini take to grow

What we pick is only the fruiting body; the mycelium itself lives in the soil for years. When conditions turn moist and warm, a tiny mushroom primordium forms on it, and before you know it, it's growing right before your eyes.

The rough timeline looks like this:

• The first 2–3 days the mushroom is barely visible: a small, firm little cap about the size of a nut.
• The next 3–5 days it actively gains mass, with the cap and stem getting thicker literally by the day.
• By day 6–9 the porcini reaches its full size.

So from a tiny primordium to a big, sturdy mushroom takes roughly a week. Faster in warm, humid weather, slower when it's cool.

How many days after rain do porcini appear

Rain is the trigger, but not an instant one. The mycelium needs time to “switch on” and grow a fruiting body.

Usually the first porcini appear 5–7 days after a good warm rain, and the main flush comes on day 7–10. If it turns sharply colder after the rain, you'll have to wait longer. We wrote more about this in the article when to go mushroom hunting after rain.

How much does a porcini grow in a day

At the peak of growth, a young porcini adds roughly 1–2 cm in height per day, and even more noticeably on a warm night after rain. That's exactly why experienced foragers say mushrooms “grow at night”: in the cool, damp night air growth is at its most active, and by morning a full-sized mushroom stands where yesterday's tiny one was.

How long does a porcini live

The fruiting body of a porcini doesn't live long. A young, firm porcini holds up for about a week to a week and a half, and then it starts to age: the cap turns spongy, the tube layer goes yellow and green, and larvae move into the stem.

So the “window” when a mushroom is still young and clean is fairly narrow — just a few days. Arrive late and you'll find an overgrown, maggoty mushroom. More on why old mushrooms aren't worth taking in the article why you shouldn't pick old and maggoty mushrooms.

What growth speed depends on

The same mycelium can produce a mushroom in five days or in ten. The main factors:

• Warmth. At +15…+20 °C growth is fastest; in the cold it slows down.
• Moisture. After rain and in foggy weather mushrooms grow actively; in drought they stall.
• Age of the mycelium. On a mature, well-developed mycelium mushrooms come up together and grow faster.

And porcini, like all forest mushrooms, grow in waves, or “flushes”. We explained why in the article why mushrooms grow in waves.

Sources

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