How fast honey fungus grows, and when it appears after rain

There's a reason people say of honey fungus: “empty one day, a full bucket the next.” These mushrooms don't come up one by one but in big, tight-knit clusters, and they grow so fast that within a couple of days a stump is covered in a solid carpet. Let's look at how many days honey fungus takes to grow, when to expect it after rain and why it seems to “shoot up” all at once.

How many days honey fungus takes to grow

Honey fungus grows faster than most forest mushrooms. From the moment tiny caps on thin stems appear on a stump to fully grown mushrooms takes just 3–5 days.

They don't grow singly but in colonies: the mycelium wraps around dead wood and sends up dozens of fruiting bodies at once. So honey fungus is either there or it isn't — there's hardly ever an in-between.

How many days after rain honey fungus appears

Autumn honey fungus is very sensitive to moisture and cool temperatures. It usually appears 7–10 days after a good rain, once the damp, mildly warm weather of late August to September settles in.

The classic trigger is a warm, damp night after the first autumn rains. More on how it depends on rainfall in the article when to go mushroom picking after rain.

Why honey fungus seems to grow overnight

At the height of a flush, young honey fungus stretches up very fast, especially at night in the cool and damp. A forager who saw only tiny “pinheads” on a stump yesterday finds a ready cluster there the next morning. It's not magic, just ordinary nighttime growth — the same as with porcini.

How long honey fungus lives

A honey fungus fruiting body doesn't live long — about a week. Young ones with a rounded cap and a “skirt” on the stem are the tastiest. After that the cap opens up and flattens, and the mushroom turns tough and dries out.

Since honey fungus grows in flushes, timing matters: one flush lasts one or two warm, damp weeks, and then it needs fresh rain. We explained why in the article why mushrooms grow in flushes.

What affects growth speed

• Cool and damp. Honey fungus loves +10…+15 °C and humid air; in this weather it comes up most abundantly.
• The state of the wood. The more dead stumps and fallen trunks there are, the richer the colony.
• Time of season. Autumn honey fungus peaks in September and early October, until the first serious frosts.

And remember the main danger: honey fungus has poisonous lookalikes. We explained in detail how to tell them apart in the article false honey fungus: how to tell it from the real thing.

Sources

• “Vyznachnyk hrybiv Ukrainy” (Guide to the Fungi of Ukraine; Kyiv, Naukova Dumka publishing house).
• Armillaria mellea in the GBIF database, the global biodiversity database.
• Honey fungus on Wikipedia.