Just guessing is totally fine – it's only about a first impression.
All four help a little. But the harvest month is decided when you buy the seed – and whoever finishes in September instead of October never stands in the long rain at all. Outdoors, the most important decisions fall before the seed is in the ground.
Outdoors you're given light at an intensity that costs serious equipment indoors. In exchange you give up something you take for granted inside: every single control.
No timer. No exhaust fan. No humidifier. No thermostat. The weather does what it wants and you watch.
That sounds like losing control. Not quite – control doesn't disappear, it moves to the start of the season.
Indoors you set 12/12 and it stays 12/12 – identical week after week.
Outdoors it's the other way round. In June the sun in Germany delivers a monthly average of about 45 mol per square metre and day – the league of strong indoor setups. By September it's around 24, in October about 12.
A quarter. And precisely in the weeks when your plant is flowering and the buds are meant to fill. The sun is generous in summer and stingy in autumn – your plant needs it the other way round.
Outdoors your plant gets something no lamp fully delivers: the whole solar spectrum, UV included. The conclusion suggests itself – more UV, more active compound.
Does it hold?
No, at least not for modern varieties. A 2021 measurement series found no UV-driven increase in cannabinoids at all. The evidence always cited against that is from 1987, found under 10 percent increase – and did so on old genotypes with under 3 percent THC.
More interesting than the refutation is where the rule comes from. In the archive of the scene magazines it first appears in December 1981 – not in an article but in a lamp advertisement: „Patented to produce beneficial ultraviolet for high THC and full flowering." The same ad ran for four months.
And in 1986 the very same magazine printed the caveat alongside it: the researcher quoted was „unsure whether UV-B radiation directly stimulates THC production" – the compound acting rather as the plant's UV screen. Cause and effect were already swapped back then: the plant protects itself, it does not supply you.
In 2018 it still reads „the running theory holds…". A sales pitch from 1981 that has outlived its own caveat by more than three decades – and is older than most of the people passing it on.
Tap the left side first, then the matching item on the right.
Three of four controls become decisions made once: where do I plant, which variety, when do I put them out. Only one stays in your hand all season – the watering can. Plus the harvest date, but that comes at the very end.
The other courses give clean figures: at 30 °C a spider mite needs about seven days from egg to adult. Such values come from the lab, where temperature stays constant.
Outdoors nothing stays constant – and that makes things faster, not slower. Under fluctuating temperatures between 12.5 and 27.5 °C an aphid population doubled in 1.95 days instead of 2.70. The fluctuation itself accelerates.
Cold nights slow things the other way: a fungus gnat needs about 21 days for its cycle at 22 °C, about 40 at 16 °C.
Outdoors, treat the figures from the other courses as a range, not a value.
Timer, exhaust, humidifier, thermostat – all gone. You don't make the humidity outdoors, nor the vapour pressure deficit. So what is even left in your hands?
Two things. The watering can and the harvest date.
That sounds like little, but the weighting is exactly right: both are powerful. Your watering rhythm is your only answer to hot, dry days. And in autumn the harvest date is the last screw you can still turn – when everything else has long been decided.
Tap the steps in the correct order.
What stands out is how early the important things happen. The first three decisions fall before the plant is really growing – and afterwards almost none of them can be corrected.
🎯 Hands-on mission
Start a grow diary for your outdoor season and note three things right at the beginning: which variety, which site, which planting-out date. Those are exactly the three decisions you can't change later – and next year you'll want to know how you made them.
Start a grow diary →✓
One control hasn't vanished, it's just due earlier: the timer sits inside the seed. What that means decides your harvest month.
Something still unclear?
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