Horticulture reference

Cannabis flowering stage

Flowering is the documented phase of the cannabis life cycle in which the plant stops adding vegetative material and shifts energy into reproductive structures. For photoperiod cultivars the stage is documented as running eight to ten weeks from the photoperiod flip; autoflowers are documented as moving into flower on their own internal schedule around week three to four of life. The variables described as affecting yield in published references are the timing of the flip, management of the first three weeks of stretch, the documented feed program through the bulk phase, and the timing of the chop. This reference walks through each in the order published protocols describe them.

How 12/12 triggers the flowering response

For a photoperiod plant, the documented flowering trigger is dropping the light cycle to 12 hours on and 12 hours off. Published references describe the dark period as requiring absolute darkness — a streetlight leak through a tent zipper or a power LED on a fan controller is documented as sufficient to disrupt the response and induce re-vegetation or stress-related morphological changes. Published protocols describe taping over indicator LEDs and verifying the tent at midnight with the light off. The schedule change itself is documented as best made abruptly rather than gradually; ramping the schedule across days is described as offering no functional benefit and delaying the response.

Autoflowers are documented as not requiring a flip. Published material describes them running 20/4 from seed to harvest with the flowering response triggering on the plant's own clock around day 21 to 28. An accidental flip is documented as not catastrophic, but published reports describe a yield loss with no compensating benefit.

The stretch phase as documented

Weeks one through three of 12/12 are documented in published references as the stretch — the period during which a photoperiod plant is documented as roughly doubling in height while vegetative mass stops accumulating. The stretch is described in grower reports as the moment many home growers run out of headroom, scorch top colas under the fixture, or watch the canopy go uneven as one or two phenotypes stretch harder than the rest. Documented corrective tools are light defoliation, super-cropping, and raising the fixture. Super-cropping is documented as bending a tall cola and pinching the stem above the bend to break inner fibres without breaking the outer skin; published reports describe the plant hardening a knuckle there within five days and stretch slowing at that site. Documented LED clearance through the stretch sits at 45 to 55 cm above the canopy.

White hairs — the pistils — are documented as emerging at the nodes by the end of week one, with the first bud sites visibly forming by week three. After week three, published references describe the stretch as essentially complete, with no meaningful height gain expected. Aggressive defoliation, where described as appropriate, is documented as best executed in week three — pulling fan leaves shading interior bud sites and leaving the rest.

Week-by-week development in published references

From week four onward the documented phase is bulk. Published references describe the buds putting on most of their final weight between weeks four and seven, calyx by calyx, while the pistils gradually shift from bright white to amber and curl inward. The buds are documented as hardening, the sugar leaves frosting with trichomes, and the aromatic profile shifting from green and grassy to whatever the strain literature describes — fruit, fuel, gas, citrus, whichever the breeder documentation lists. Week six is documented as the peak terpene-volatility window.

Week eight is documented as the inflection point for most eight-to-ten-week strains. Pistils are described as mostly amber and curled, the calyxes documented as fat and tight, and the trichomes under a loupe documented as starting to turn cloudy. Published protocols describe adding seven to fourteen days from this point depending on the breeder's published flowering time and the trichome read. Strains marketed at ten weeks of flower are documented in grower reports as almost always needing the full ten — pulling at eight is described as costing both final weight and a less-developed cannabinoid profile.

Calcium and magnesium in flower

Flower is documented as the phase where calcium and magnesium deficiencies appear most often, particularly under LED light and particularly in coco or with reverse-osmosis water. The documented signal is rust-coloured spots on mid-canopy fan leaves around week three, sometimes progressing to interveinal chlorosis on the same leaves by week five. The published response is a cal-mag supplement at 0.5 to 1 ml per litre on every feed — not just deficient feeds — from the flip onward. Where tap water provides background calcium, published references describe lighter dosing with a runoff EC check before adding more.

Potassium demand is documented as rising through flower. Published protocols describe switching from veg nutrients to a bloom line by the end of week two, with most bloom lines documented as carrying the PK ratio without separate boosters. PK booster powders in week four to six are documented as adding small amounts of bulk where the line responds to them — many modern bloom nutrients are documented as already containing the same elements, and stacking is described as wasteful at best and a nutrient lockout at worst.

The late-flower flush debate

Flushing in the last seven to fourteen days of flower — running plain water at pH 6.0 instead of nutrient solution — is one of the longest-running debates documented in home-growing literature. The case for flushing described in published references is that residual nutrients in the bud produce a darker ash and harsher combustion profile; the case against is that controlled studies on cannabis have not documented a meaningful difference in tested combustion characteristics between flushed and unflushed plants when the cure is properly executed. The compromise documented in many grower reports is a partial flush — dropping nutrient EC by half for the last ten days rather than going to plain water — described as giving the plant something to metabolize without overloading the buds. The cure is documented as having a much larger effect on final quality than the flush.

Documented signals for end of cycle

The documented harvest window is when the trichomes are mostly cloudy with about 10 to 20% amber when viewed under a 60x jeweller's loupe. Pure clear is documented as indicating the plant is not yet finished. Pure amber is documented as indicating the window has passed, with THC having degraded toward more sedating CBN in laboratory measurements. The documented sweet spot is cloudy-dominant with the first amber starting to show, and on a strain finishing at ten weeks of flower this is documented as typically falling between day 63 and day 70 of 12/12. Pistil colour is documented as a rough guide; trichome colour is described as the actual call.

Lockbox Seeds publishes reference material about cannabis horticulture for educational purposes only. Cannabis cultivation is governed by jurisdiction-specific laws that change frequently; readers are responsible for understanding the legal status of cannabis in their location.