ML MycologyLog Resource Shiitake Block Timing Guide

Shiitake Block Readiness (3790) Browning vs Early Fruiting

A practical decision point: when to keep the block sealed to finish browning, and when to unwrap, soak, and move to fruiting conditions.

Strain: 3790 Incubation Browning / Rind Fruiting

Grower Question

“Should I unwrap + soak now, or keep it sealed to finish browning?”

Block Specs

Substrate
19.7 oz 100% OSD + 2 oz oats
Spawn
29 oz grain spawn
Total weight
~80 oz (≈ 5 lbs)
Strain
3790
Incubation
5 weeks @ ~70°F (dark)
Current state
Popcorning, brown tips, still mostly white

The block is producing ~20 popcorn-like projections. Some tips are turning brown, but the overall surface is still white. The question is whether to begin fruiting (unwrap + soak + move to humidity/light), or keep it in the bag until browning/rind formation completes.

MycologyLog Guidance

For 3790, timing the rind is the whole game.

Recommendation

Short answer

Don’t unwrap or soak yet — leave it sealed and let browning/rind formation finish.

Why you’re seeing “popcorning” now

Those popcorn projections with early brown tips are a sign of early morphogenesis, not full fruiting readiness. With 3790, it often means the block is healthy and transitioning toward forming the protective rind (skin) it needs to fruit well.

  • Healthy mycelium starting to differentiate
  • Bag environment promoting the browning/rind phase
  • Early “preview” structures that often stabilize as the rind forms

Why soaking too early backfires

If you unwrap and soak before the rind hardens, you often get soft blocks that fruit irregularly.

  • Blobby / deformed fruits
  • Side-pin chaos
  • Weak caps / cracked stems
  • Lower overall yield

What “ready” looks like (3790 checklist)

Surface color

Aim for 70–90% brown coverage.

Texture

Dry, firm, “cork-like” rind.

Block behavior

Slight shrink; pulls away from bag.

New growth

No fresh white mycelium pushing outward.

With a small oat supplementation, it’s normal for browning to take another 7–14 days depending on genetics and bag conditions.

What to do right now

  • Keep the block sealed in the bag.
  • Hold 65–72°F. Light is not required yet.
  • If condensation is heavy, add 1–2 micro-vents (tiny pinholes) to reduce pooling.
  • Do not cut slits, fully open, or soak until the rind is formed.

Bottom line

Those popcorns are a preview, not a green light. Finish browning first, then trigger fruiting with a soak/cold shock.