How fast slippery jacks grow, and when they appear after rain

The slippery jack is a mushroom in a hurry. In young pine woods after a warm rain it comes up en masse and grows so fast that foragers can fill a basket within a couple of days, while a week later the same spot is full of overgrown ones. Let's look at how many days a slippery jack takes to grow, when to expect it after rain and why it likes to grow in company.

How many days a slippery jack takes to grow

Slippery jacks have thin flesh and love moisture, so they grow fast. From a tiny cap to a full-grown mushroom takes just 3–5 days, and even less in warm, damp weather.

They usually grow in groups: one small clearing in young pine woods can hold dozens of slippery jacks of different ages. That makes them quick and easy to pick.

How many days after rain slippery jacks appear

The slippery jack is very responsive to moisture. The first mushrooms appear as soon as 3–5 days after a warm rain — noticeably faster than porcini, which need a week. That's why slippery jacks are often the first catch after summer downpours.

They grow best among young pines 10–20 years old. More on when to head out for them in the article slippery jacks after rain: when to go to the forest.

Why slippery jacks come up en masse and “overnight”

The slippery jack's mycelium is linked to pine roots (a symbiosis called mycorrhiza) and spreads beneath young trees. When moisture arrives, it sends up many fruiting bodies at once — hence the mass flushes.

And like all mushrooms, slippery jacks grow most actively at night, in the cool and damp. So a clearing that was empty in the evening may greet you in the morning with dozens of young, glossy caps.

How long a slippery jack lives

A young slippery jack doesn't last long — about 5–7 days. While the mushroom is young, its cap is convex and the underside is covered by a pale veil. Later the veil tears, the tube layer turns yellow, and the mushroom ages and often gets wormy — its thin stem attracts larvae faster than almost any other mushroom.

So don't dawdle with slippery jacks: pick them young and process them the same day, because they barely keep fresh and spoil quickly.

What affects growth speed

• Moisture and warmth. After a warm rain at +15…+20 °C, slippery jacks grow fastest.
• Age of the pine stand. They're most abundant in young, sunny pine woods where the mycelium is active.
• Flushes. Slippery jacks come up in waves: one flush after rain, then a pause until the next.

Sources

• “Key to the Fungi of Ukraine” (Kyiv, Naukova Dumka publishing house).
• Suillus luteus in GBIF, a global biodiversity database.
• Slippery jack on Wikipedia.