We’ve been collecting grow-schedule comparison data from US customers running our
autoflower line, and one Amnesia Auto comparison from a customer’s split-tent run was
clean enough to share. Same pack, same setup, only variable was 20/4 vs 18/6 light
schedule — start to finish.
Posting the data here so anyone considering switching schedules has something to look at
besides forum hot takes. Photos and write-up courtesy of the grower who ran the
side-by-side.
Setup (identical on both sides)
| Variable | Spec |
|---|---|
| Strain | Amnesia Auto (same pack, popped same day) |
| Tent | 4×4 split with reflective divider |
| Light | Spider Farmer SF-2000 each side, 200W full draw |
| Medium | Coco/perlite 70/30, 5gal fabric pots |
| Nutes | GH Trio + CalMag, EC ramp 0.8 → 1.6 |
| Temp / RH | 76°F day, 68°F night, 55% RH veg → 45% flower |
| Water | RO + CalMag back to ~150ppm baseline |
Only difference: Plant A on 20/4, Plant B on 18/6 from day 1 to chop.
Week-by-week notes (from the grower’s log)
Weeks 1-3 (veg): Almost identical. Plant A (20/4) maybe 1cm taller by end of week 3,
but within margin of error. Both threw their first pre-flowers around day 21.
Weeks 4-6 (stretch + early flower): This is where it diverged. Plant A stretched
harder — final height 94cm vs 81cm on Plant B. More internodes too. Plant B stayed
compact, less LST needed.
Weeks 7-9 (bulk): Plant A bulked faster but trichomes turned cloudy 4 days earlier.
Plant B took the extra 4 days but produced denser, slightly heavier individual colas.
Weeks 10-11 (finish): Plant A done day 73. Plant B done day 78.
Final numbers (after 14-day dry, 7-day cure jar weight)
| Metric | 20/4 (Plant A) | 18/6 (Plant B) |
|---|---|---|
| Final height | 94 cm | 81 cm |
| Seed-to-chop | 73 days | 78 days |
| Dry yield | 87 g | 79 g |
| Top cola weight | 18 g | 21 g |
| Trichome ratio at chop | ~80% cloudy / 15% amber | ~70% cloudy / 25% amber |
| Smoke (grower’s notes) | Sharper, more haze-forward | Rounded, fuller terps |
So 20/4 won on raw yield by ~10% and finished 5 days faster. But 18/6 produced denser
top colas and (per the grower, jar-cured 30 days) a more developed terp profile. Power
bill differential: 20/4 ran ~$11/month more on light alone in this setup, before A/C
delta.
Takeaway
If you’re optimizing for grams per kWh, 18/6 is probably the move. If you’re
optimizing for grams per calendar day in a perpetual rotation, 20/4 wins. The
“autos don’t sleep” purists and the “all plants need dark for respiration” purists are
both sort of right and sort of wrong — the difference is real but smaller than either
side claims.
Caveats: this is one customer’s split-run, single strain, indoor coco. Outdoor or
organic soil could behave totally differently. Sativa-dominant autos like Amnesia might
respond differently than indica-leaning ones. We’ll add more customer comparisons to
this thread as the data comes in.
Question for the room
What schedule are you running on autos right now and why? Especially curious to hear
from anyone who’s done this comparison on indica-dominant autos (like a kush or GG
line) — does the gap close, widen, or flip?
If anyone’s tried 6/2 or other unconventional schedules with autos, drop your
results — happy to add credible comparison runs to this thread with full credit.