Multi-Flush Guide
Getting multiple harvests from one substrate — rest periods, rehydration, cold shocking, and maximising total yield.
What Is a Flush?
A "flush" is a single cycle of mushroom fruiting. After you harvest all the mature mushrooms from your tub, the mycelium rests briefly and then produces another crop of mushrooms. Each successive crop is called a flush. Most substrates can produce 3–5 flushes before the nutrients are exhausted.
After Harvest: Starting the Rest Phase
Immediately after you finish harvesting all mushrooms (including aborts) from a flush:
- Clean the surface. Remove all harvested stumps, aborts, and any debris from the substrate surface. Leaving dead mushroom tissue on the surface invites contamination.
- Open the controller dashboard.
- Click "Rest" on your tub's control panel. This switches the controller to Rest mode, which reduces fan activity and maintains high humidity to keep the substrate hydrated while the mycelium recovers.
Tip: The Rest phase typically lasts 24–48 hours. During this time, the mycelium consolidates its network and prepares to produce the next flush. The controller manages this timing automatically.
Rehydration (Dunk/Soak)
Each flush depletes moisture from the substrate. Rehydration between flushes replaces this lost water and is one of the most important steps for maintaining yields across multiple flushes.
Dunking Method
- After harvest, fill the tub with clean, cool tap water. Pour water gently down the side of the tub to avoid damaging the substrate surface. Fill until the water level is just above the substrate surface.
- Weight the substrate down. The substrate cake will float. Place a clean plate or another tub lid on top to keep it submerged.
- Soak for 6–12 hours. A 6-hour soak is sufficient for most situations. Up to 12 hours is fine for very dry substrates. Do not exceed 24 hours — prolonged soaking encourages bacterial contamination.
- Drain the water. Tilt the tub carefully and pour off all the excess water. You can prop one end of the tub up for 15–30 minutes to let it drain completely.
| Soak Duration | When to Use |
|---|---|
| 6 hours | Standard rehydration between flushes. Works for most situations. |
| 8–12 hours | Substrate feels noticeably lighter or dryer than when you started. Visible shrinkage or pulling away from tub walls. |
| Skip dunking | If substrate still feels heavy and well-hydrated. Some growers skip the dunk between flush 1 and 2 if conditions have been well-maintained by the controller. |
Warning: Do not use warm or hot water for dunking. Cool tap water (roughly 10–15°C / 50–60°F) works best. Some growers intentionally use cold water to double as a cold shock (see below).
Controller Auto-Transition
The controller is designed to handle the flush cycle transitions automatically:
- Rest phase — triggered when you click "Rest" after harvest. The controller reduces FAE and maintains high humidity. Duration: 24–48 hours (configurable in your strain profile).
- Cold Shock phase — the controller automatically transitions from Rest to Cold Shock. If you have a heater connected via smart plug, the controller will turn it off and may activate fans to bring the temperature down. The target is a drop of 5–10°C below the normal fruiting temperature. Duration: 12–24 hours.
- Pinning / Fruiting phase — after the cold shock period, the controller automatically transitions back to fruiting conditions. Temperature returns to normal, FAE increases, and humidity is optimised for pin formation.
This entire cycle — Rest, Cold Shock, Pinning, Fruiting — happens automatically. You only need to click "Rest" after harvest and optionally perform the dunk between Rest and Cold Shock.
Tip: The cold shock mimics the natural temperature drop that triggers pinning in the wild (such as a cool night after rain). It is not strictly required — many flushes will happen without it — but it tends to produce a more uniform and larger pin set.
Flush-by-Flush Expectations
Each flush typically produces less than the previous one as the substrate's nutrients are depleted. Here is what to expect for a standard cubensis monotub grow:
| Flush | Relative Yield | Timing (from previous harvest) | Notes |
|---|---|---|---|
| 1st flush | 100% (baseline) | First harvest at 5–10 days after fruiting starts | Usually the largest and most uniform flush. |
| 2nd flush | 60–80% | 7–14 days after 1st harvest | Often produces fewer but larger individual mushrooms. |
| 3rd flush | 40–60% | 7–14 days after 2nd harvest | Yields decrease noticeably. Still worthwhile. |
| 4th flush | 20–40% | 10–18 days after 3rd harvest | Smaller yield, often with irregularly shaped fruits. |
| 5th flush | 10–25% | 14–21 days after 4th harvest | Minimal yield. Many growers stop here. |
Tip: The first two flushes typically account for 60–70% of your total yield. The effort required for flushes 4 and 5 is the same, but the returns diminish significantly. Most growers run 3–4 flushes before retiring the substrate.
When to Retire the Substrate
It is time to dispose of your substrate and start fresh when you see any of the following:
- Contamination appears. Green mould (trichoderma), black mould, or other coloured contamination on the substrate surface. Once contamination is visible in a fruiting tub, it is usually too late to save it. Discard immediately.
- Yields drop below worthwhile levels. If a flush produces only a handful of small mushrooms after a 2-week wait, the substrate is spent.
- Substrate is heavily decomposed. The substrate has turned dark, spongy, and has shrunk significantly from its original volume. It no longer holds structure.
- Persistent bacterial issues. If mushrooms are consistently showing bacterial blotch (slimy, discoloured caps) or the substrate smells sour, bacteria have taken over.
- No pins form after 3+ weeks despite proper conditions and cold shocking.
How to Dispose of Substrate
- Compost it. Spent mushroom substrate is excellent for garden compost. It is rich in organic matter and partially decomposed.
- Garden beds. Bury spent substrate in outdoor garden beds. You may even get bonus outdoor flushes if conditions are right.
- Green waste bin. If you do not garden, dispose of it in your green waste or organic waste collection.
Warning: If the substrate is contaminated (especially with trichoderma), bag it securely before disposing. Do not compost heavily contaminated substrate near your growing area, as trichoderma spores can persist in the environment and contaminate future grows.
Tips for Maximising Flush Count
- Start with a thick substrate layer (7–10 cm). Thicker substrate holds more moisture and nutrients, supporting more flushes.
- Rehydrate between every flush. The dunk is the single most important step for subsequent flushes.
- Use the controller's cold shock feature. The automated temperature drop helps trigger robust pin sets on each flush.
- Remove all aborts and stumps after each harvest. Decaying tissue invites contamination.
- Keep the growing area clean. Wipe down the exterior of the tub and the area around it between flushes.
- Monitor with the controller. Watch for sensor readings that indicate problems (sudden humidity drops, temperature swings) and address them promptly.