How many flushes can you get from a mushroom grow kit?

Most people harvest the first flush from their grow kit, eat well, and assume the kit is done. That’s leaving a little yield on the table — most kits are capable of a good second flush. Mondo recommends going no further than that second flush, for safety reasons, so this guide focuses on how to get the most out of flush two.

This guide covers what a flush actually is, how much yield to realistically expect, and the exact steps to trigger a strong second flush from your kit.

What Is a “Flush,” Exactly?

A flush is one complete fruiting cycle: pins form on the substrate, develop into mushrooms, and are harvested — after which the mycelium rests before it’s ready to fruit again. A grow kit has enough stored nutrients for several of these cycles, but Mondo recommends stopping after the second flush for safety reasons — see “Why we recommend stopping at flush two” below.

How Much Yield Should You Expect Per Flush?

This is where a lot of growers get their expectations wrong. Yield doesn’t drop off a cliff after flush one, but it does decline steadily, and that’s completely normal — it’s not a sign of a failed grow.

Across cultivation data for cubensis-type kits, the pattern generally looks like this:

• First flush: roughly 40–60% of the kit’s total lifetime yield
• Second flush: roughly 30–50% of the first flush’s weight
• Third and fourth flush: substrate can technically keep producing smaller flushes after that, but this falls outside Mondo’s recommended use of the kit — see below before deciding whether to continue

In other words: if your first flush produced a generous harvest, your second flush should still be very much worth the effort — and that’s where we recommend you stop.

If a flush produces nothing at all after about three weeks of proper fruiting conditions, the kit has run its course.

How to Trigger a Second Flush

The good news: you don’t need anything you don’t already have. The tub your kit came in is exactly what you’ll use again.

1. Clean up the substrate. Remove any leftover stems, broken caps, and loose mycelium debris from the surface. This step matters more than people think — leftover organic matter sitting on a moist substrate is the single most common cause of contamination on a second flush.
2. Let it rest for 24 hours. Leave the tub open, without the grow bag on it, at room temperature. This gives the mycelium a short recovery window before rehydration.
3. Rehydrate in the tub. Pour cold, chlorine-free water directly into the tub until the substrate is fully submerged — the same way you activated it the first time. If it floats, weigh it down with a clean plate.
4. Soak for 9–24 hours, then carefully drain the water and let the substrate sit for 15–30 minutes until it stops dripping.
5. Close the tub back up and set it inside a fresh (or cleaned) grow bag, exactly as you did for the first flush.
6. Mist once or twice daily to keep humidity high without soaking the substrate directly, and keep the kit at 23–27°C, never exceeding 27°C — the same range as the first flush — out of direct sunlight.
7. New pins typically appear within 1–2 weeks — sometimes a little slower than the first round.

Why We Recommend Stopping at Flush Two

You may come across advice elsewhere suggesting a third or fourth flush is standard practice. Mondo’s grow kit manual specifically recommends going no further than a second flush, for safety reasons: each extra round of rehydrating an already-used, no-longer-sterile substrate widens the window in which contaminants can establish themselves, and by this point the substrate has also given up most of the nutrients that kept mould pressure in check during the first two rounds. If you choose to try a further flush anyway, you’re going beyond our tested guidance — inspect the substrate closely before and during rehydration, and discard immediately at the first sign of green, black or pink discolouration or an off, sour smell.

Why a Second Flush Sometimes Fails

If a rehydrated kit doesn’t produce anything, it’s almost always one of these:

• Contamination — visible green, black, or pink discolouration, or a sour/musty smell. If you see this, discard the substrate; there’s no salvaging a contaminated flush.
• Poor airflow — a grow bag with restricted air exchange can suffocate the mycelium even if temperature and humidity look fine.
• Substrate exhaustion — sometimes a kit has genuinely given everything it has after two flushes. This is a normal, expected outcome, not a mistake on your part.

Frequently Asked Questions