What to track in a mushroom grow log (and why)
The point of a grow log isn't to fill in cells — it's to answer three questions later: which batches yielded best, which are running late, and what keeps contaminating? These columns are the minimum that let you answer all three. They're also exactly what the Mycro Grow Log records.
| Column | Why it earns its place |
|---|---|
| Batch ID / label | One row per block or bag so you can trace a result back to a specific grow. |
| Species & strain | Timelines and yields differ hugely by species — you can only benchmark like against like. |
| Substrate | Masters Mix, straw, supplemented sawdust — the biggest lever on yield and contamination. |
| Spawn type / ratio | Higher spawn ratios colonize faster; logging it explains why two blocks finished days apart. |
| Inoculation date | Day 0. Every "days in stage" and overdue flag is measured from here. |
| Dry substrate weight | The denominator for biological efficiency. Weigh it dry, before hydrating. |
| Colonized date | Marks the end of the spawn run — compare it to the typical range to catch a slow block. |
| Pinning / fruiting date | When you introduced fruiting conditions and pins appeared — tunes your timing next round. |
| Harvest date & fresh yield | The payoff. Log each flush; fresh weight (grams or lb) drives the BE calculation. |
| Biological efficiency (%) | Fresh yield ÷ dry substrate × 100 — the one number that tells you if a grow was good. |
| Contaminated? + cause/stage | Note green mold, bacteria, the stage it showed. Tallying causes is how you fix your loss rate. |
| Notes | Anything unusual — a temperature swing, a new supplier, a strain quirk. Future-you will want it. |
The one calculation people get wrong: biological efficiency
Biological efficiency (BE) is how you compare a good grow to a bad one on a level field. The formula:
Example: 1.2 kg of fresh oysters from a 1.5 kg dry block = 80% BE. Oysters often run 75–100%+, lion's mane ~50–75%, shiitake ~75–125%.
In a spreadsheet you add a formula column (=fresh_yield/dry_weight*100) and keep your
units consistent. It's easy to fumble — mixing grams and kilos, or forgetting to weigh the substrate
dry — which is the single most common reason a manual log gives numbers you can't trust. See the full
biological efficiency guide.
Spreadsheet template vs. an auto-calculating log
Both are valid. Here's the honest trade-off so you pick the right one for where you are:
| CSV / spreadsheet template | Mycro Grow Log | |
|---|---|---|
| Cost | Free | Free, no login |
| Biological efficiency | You write the formula | Calculated automatically |
| Days-in-stage / overdue flag | Manual date math | Automatic per batch |
| Contamination rate | You tally it | Tallied for you |
| Setup | Download & format | Open the page, add a batch |
| Best for | A few batches, full control | Anyone tired of the manual math |
The honest rule of thumb: start with the template if you like a spreadsheet and only have a handful of grows. Switch to a purpose-built log the moment you're re-typing the BE formula, eyeballing which blocks are overdue, or losing track of which cause is contaminating you — that's when the bookkeeping starts costing more time than it saves.
Skip the spreadsheet math — free Grow Log
Mycro's Grow Log uses the same columns as this template but does the work for you: log an inoculation and a harvest weight, and it calculates biological efficiency, counts the days in each stage, flags an overdue block, and tallies your contamination rate — no login, no limit, saved in your browser. Export back to CSV any time.
Try the free Grow Log → Become a Founding Grower — $99 →Free Grow Log — no login, no limit. Or become a Founding Grower for $99 once: a sign-in account today, lifetime founder pricing, fully refundable any time.
Frequently asked questions
What should a mushroom grow log template include?
A useful mushroom grow log tracks, per batch: a batch ID or label, species and strain, substrate and spawn type, the inoculation date, dry substrate weight and number of blocks, the dates it finishes colonization and starts pinning, each harvest date and fresh yield, the biological efficiency (fresh yield divided by dry substrate weight), whether the batch contaminated and at which stage, and free-text notes. Those fields let you calculate biological efficiency, spot batches that are overdue to colonize, and find the root cause of contamination.
Is there a free mushroom grow log template?
Yes. You can download a free CSV mushroom grow log template from this page and open it in Excel, Google Sheets or Numbers. It comes with the recommended columns and two example rows. If you would rather not maintain the spreadsheet math by hand, Mycro's free web Grow Log uses the same fields and calculates biological efficiency, days-in-stage and contamination rate for you automatically, with no sign-up.
How do you calculate biological efficiency in a grow log?
Biological efficiency (BE) is the total fresh mushroom yield divided by the dry substrate weight, expressed as a percent: BE = fresh yield ÷ dry substrate weight × 100. For example, 1.2 kg of fresh oysters from a 1.5 kg dry block is 80% BE. In a spreadsheet you add a formula column; in the Mycro Grow Log it is computed automatically the moment you log a harvest weight.
Spreadsheet or app for a mushroom grow log?
A spreadsheet template is free and flexible and is fine when you are experimenting with a handful of batches. It starts costing you time once you are re-typing the biological-efficiency formula, manually checking which blocks are overdue to colonize, and tallying contamination by cause. A purpose-built log does that math automatically. The honest rule: start with the template, and switch to an app when the manual bookkeeping costs more time than it saves.
General guidance from common cultivation practice, not guarantees — your numbers vary with strain, substrate, technique and conditions. Mycro is for legal culinary & medicinal mushrooms only.