In which weeks of flower do buds grow the most?

Q: In which weeks of flower do buds grow the most?

Cannabis buds put on most of their mass from roughly week 3 to week 7 of flower, counted from the first pistil clusters, and keep gaining weight and resin right through the final weeks. In one controlled trial, inflorescence dry weight kept increasing at every harvest from week 5 to week 11. That is why the last weeks need full light and feed: taper nitrogen, don't flush.

Short answer

Cannabis buds put on most of their mass from about week 3 to week 7 of flower (counted from the first pistil clusters), and they keep gaining weight and resin to the end. In a controlled trial, inflorescence dry weight rose at every harvest from week 5 to week 11 ^[1]. Supported that growth continues late; the week-by-week split is Grower practice.

Why

The first two to three weeks after the flip belong to the stretch: stem elongation peaks around days 5–10 of short days, then the shoot tip condenses into a cola ^[3]. Little bud mass is built yet.

Once internodes stop lengthening, the plant puts its effort into bracts and flowers. That's the bulking phase most growers see from about week 3.

It doesn't stop when the calendar says "ripening". Dry weight kept climbing through 11 weeks in one indoor genotype ^[1], and trichomes keep developing as flowers age ^[2].

House position: the final weeks are when the plant packs on much of its final weight and resin. Pre-harvest flushing and darkness are Myths that starve it at exactly the wrong time.

More light means more bulk: yield rose linearly with canopy PPFD ^[4].

The numbers

Weeks of flower (typical 8–10 week cultivar)	What's happening
Flip to ~day 14	transition and stretch; pistil clusters appear
Weeks 1–3	stretch slows, colas form
Weeks 3–7	fastest visible bulking
Final 2–3 weeks	bracts swell, resin ripens, weight still rising ^[1]^[2]

What to do

Count from the first pistil clusters, and log the flip date too.
Keep light at full intensity to harvest.
Feed normally; taper nitrogen over the last few weeks while keeping P, K, Ca, Mg and micros.
Hold late-flower RH at 40–50 % and keep air moving through dense colas.
Check the largest buds for rot from week 6 on.

Common mistakes

Flushing for the last 1–2 weeks and losing bulk.
Harvesting by the calendar while buds are still filling.
Dimming lights for "ripening".
Ignoring humidity as buds densify.

Full article: The flip isn't day 1 of flower
How long does the flowering stage take?
How do I get bigger, denser buds?
The flush debate
Terms: flowering stage · nitrogen taper

The female reproductive organ of a flower (ovary, style and stigmas); in cannabis growers loosely call the visible white stigmas "pistils".The weight of cannabis after drying (and usually trimming), the basis growers use for yield; it is typically about 20-25% of trimmed wet weight.The stretch is the rapid increase in height in the first two to three weeks after switching to flower, when many cultivars grow 1.5 to 3 times taller.The zone of dividing cells at the very tip of a shoot (or root) that produces new leaves, nodes and stem; removing it is what topping does.The dense, elongated cluster of flowers that forms at the end of a stem or branch; the main cola tops the leader.The length of stem between two adjacent nodes; short internodes mean compact plants and tight bud stacking, long ones mean stretch.In cannabis, the small leaf-like sheath (perigonal bract) that wraps each female flower's ovary and carries the densest capitate-stalked trichomes.The genotype is the set of alleles a plant actually carries, either at one locus or across its whole genome, as opposed to the traits you can see.A hair-like outgrowth of the plant's skin; in cannabis the glandular types make and store the resin holding cannabinoids and terpenes.Feeding only plain water for days or weeks before harvest to "clean" the plant; GenetixBay rates it a Myth that harms yield, unlike a root-zone salt flush.Photosynthetic photon flux density: the number of PAR photons landing on one square metre each second, in µmol/m²/s; the standard measure of light intensity at the canopy.Gradually cutting nitrogen in late flower, toward zero near the finish, while still feeding phosphorus, potassium, calcium, magnesium, sulfur and micronutrients; GenetixBay's alternative to flushing.A micronutrient is an essential element plants need only in trace amounts, below a few mg/L: iron, manganese, zinc, copper, boron, molybdenum, chlorine and nickel.Relative humidity is the water vapour in air as a percentage of what it could hold at that temperature, so the same RH dries plants differently at different temperatures.

Follow-up questions

Do buds still grow in the last two weeks?

Yes, cannabis buds still gain weight and resin in the last two weeks of flower. In a controlled indoor trial, inflorescence dry weight kept increasing across harvests from week 5 to week 11, and trichome development continues as flowers age. This is why GenetixBay calls pre-harvest flushing and darkness myths: both starve the plant while it is still packing on weight. Taper nitrogen instead.

When does the stretch stop and bulking start?

The cannabis stretch mostly happens in the first two to three weeks after the flip, with stem elongation fastest from about day 5 to day 10 of short days. Once new internodes stay short and pistil clusters stack at the tops, the plant switches its effort to building flowers. Bulking then runs roughly from weeks 3 to 7 of flower in a typical 8–10 week cultivar.

How do I get buds to bulk up more?

To get cannabis buds to bulk up more, give them more light within reason, a healthy root zone and steady feeding through the final weeks. Yield rose linearly with canopy light up to 1,800 µmol/m²/s in a controlled trial. Keep late-flower RH at 40–50 % so dense buds don't rot, keep the dark period truly dark, and taper nitrogen rather than flushing.

Sources

Crispim Massuela D, Hartung J, Munz S, Erpenbach F, Graeff-Hönninger S, 2022. Impact of harvest time and pruning technique on total CBD concentration and yield of medicinal cannabis. Plants 11(1):140. doi.org/10.3390/plants11010140

Punja ZK, Sutton DB, Kim T, 2023. Glandular trichome development, morphology, and maturation are influenced by plant age and genotype in high THC-containing cannabis (Cannabis sativa L.) inflorescences. Journal of Cannabis Research 5:12. doi.org/10.1186/s42238-023-00178-9

Alter H, Sade Y, Sood A, et al. 2024. Inflorescence development in female cannabis plants is mediated by photoperiod and gibberellin. Horticulture Research 11(11):uhae245. doi.org/10.1093/hr/uhae245

Rodriguez-Morrison V, Llewellyn D, Zheng Y, 2021. Cannabis yield, potency, and leaf photosynthesis respond differently to increasing light levels in an indoor environment. Frontiers in Plant Science 12:646020. doi.org/10.3389/fpls.2021.646020