Flowering Cannabis: Your Essential Guide to Harvest Success
Flowering Cannabis: A Complete Week-by-Week Guide to Harvest Success
The cannabis flowering stage typically lasts 8 to 10 weeks and is divided into four key phases: pre-flowering (weeks 1–2), bud formation (weeks 3–4), rapid bud growth (weeks 5–7), and final ripening (weeks 8–10). For photoperiod plants, flowering is triggered by switching the light schedule to 12 hours of light and 12 hours of darkness. Harvest readiness is best determined by examining trichomes: mostly milky trichomes with some amber is a commonly used harvest indicator.
In this guide, we walk through what to expect each week during cannabis flowering, how to manage light, nutrients, temperature, and humidity, and how to harvest, dry, and cure your buds for the best possible result.
Key Takeaways
- Each week of the flowering stage brings distinct changes in bud development, aroma, and resin production — understanding these helps you respond at the right time.
- Trichome inspection is the most reliable method for determining when cannabis is ready to harvest.
- Proper drying and curing after harvest preserves potency, aroma, and smoothness.
Week-by-Week Cannabis Flowering
Weeks 1–2: Pre-Flowering and Early Changes
In the first two weeks of flowering, the cannabis plant shifts focus from vegetative growth to producing flowers. During this phase, small white hairs — called pistils — begin to form at the nodes where branches meet the main stem. This is an early sign that the flowering stage has officially begun.
For photoperiod plants, adjust the light cycle to 12 hours of light and 12 hours of uninterrupted darkness to trigger the flowering response. Nutrient needs shift at this stage: reduce nitrogen and increase phosphorus and potassium to support flower development. Keep temperatures between 20–25 °C (68–77 °F) with a relative humidity of 40–60%.
Weeks 3–4: Formation of Buds
In weeks three and four, visible buds begin to form, growing from the pistils that appeared in the previous phase. These buds cluster at the plant's nodes and gradually increase in size. This is a critical window for nutrient management: maintain high phosphorus and potassium levels to fuel bud development.
Continue the 12/12 light cycle without interruption. Lower humidity slightly to around 40–50% to reduce the risk of moisture-related problems as the buds begin to form. Keep daytime temperatures consistent, as fluctuating temperatures can stress the plant. Check regularly for signs of pests.
Weeks 5–7: Rapid Bud Growth
During weeks five through seven, the plant enters a phase of rapid bud development. Buds become denser, more aromatic, and coated in sticky resin. Trichome production increases noticeably during this period.
The plant has high nutrient needs at this stage — continue feeding with phosphorus-rich fertilisers. Keep humidity at around 40–45% to prevent moisture from building up in the increasingly dense buds. The ideal daytime temperature range is 20–24 °C (68–75 °F), with slightly cooler nights. Trimming lower leaves that receive little light can improve airflow and reduce the risk of mould.
Weeks 8–10: Final Ripening
The final weeks mark the ripening stage. Buds reach peak maturity, becoming plump, resinous, and dense. This is the phase to begin reducing nutrients and, for many growers, switching to plain water for the final two weeks — a practice commonly referred to as flushing — to help improve the flavour of the finished buds.
Lower humidity to 30–40% to reduce mould risk in the dense, late-stage buds. A slightly cooler temperature of 18–21 °C (65–70 °F) during this phase can help intensify colour and resin production. Monitor trichomes closely: a milky or amber appearance indicates that the plant is approaching or has reached harvest readiness.
Harvesting and Post-Flowering Care
Timing Your Harvest
The ideal harvest window is generally around 8 to 10 weeks into the flowering stage, though this varies by strain. The most reliable method for determining harvest readiness is trichome inspection using a magnifying glass or jeweller's loupe:
- Clear trichomes indicate the buds are not yet mature.
- Mostly milky trichomes with some amber are commonly associated with peak potency.
- Predominantly amber trichomes suggest THC has begun to degrade, producing a more relaxing effect.
Pistil colour can provide an additional clue — pistils that darken and curl inward indicate advancing maturity — but trichome colour is the more accurate indicator and should take priority.
Drying Your Cannabis Properly
Proper drying helps preserve cannabinoids and terpenes, retaining the potency and aroma of the finished buds. Ideal drying conditions are around 15–21 °C (60–70 °F) with 50–60% relative humidity.
Hang branches upside down or place trimmed buds on drying racks in a dark, well-ventilated space for approximately 7 to 10 days. Avoid direct heat and do not point a strong fan directly at the buds. Drying too quickly can negatively affect flavour and smoothness.
Curing for Better Quality
Curing is the final step to maximise quality after drying. Place dried buds loosely into clean, airtight glass jars, filling each jar to approximately 70–80% capacity. Store the jars in a cool, dark location.
During the first week, open the jars once or twice a day — a process often called "burping" — to release excess moisture and exchange the air. After the first week, reduce how often you open the jars while continuing to check for unusual odours, excess moisture, or signs of mould. Many growers cure for four weeks or more. Longer curing helps break down residual chlorophyll and generally improves flavour and smoothness.
Maximising Potency and Flavour
Careful timing, trichome inspection, and controlled drying and curing are the three most important factors in maximising the quality of your harvest. Rushing any of these steps is one of the most common mistakes made by beginner growers. Taking the time to dry and cure properly makes a significant difference to the final result.
Ready to start growing? Browse our cannabis seed collection or explore our beginner starter packs to find the right strain for your setup.
Frequently Asked Questions About Cannabis Flowering
When do cannabis plants start flowering?
Photoperiod cannabis plants begin flowering when they receive approximately 12 hours of uninterrupted darkness per day. For indoor growers, this transition is usually triggered by changing the light schedule to 12 hours on and 12 hours off. Autoflowering plants begin flowering based on age rather than light schedule, typically between 3 and 5 weeks after germination.
How long does the flowering stage last?
The flowering stage typically lasts between 7 and 12 weeks depending on the strain. Indica-dominant varieties often finish in 7 to 9 weeks, while sativa-dominant varieties may take 10 to 12 weeks or longer. Autoflowering varieties generally complete their full cycle in 8 to 11 weeks from germination.
What are the signs that a cannabis plant is ready to harvest?
The most reliable method is to examine the trichomes on the flowers using a jeweller's loupe or digital microscope. Clear trichomes indicate the plant is not yet ready. Milky white trichomes suggest peak THC development. Amber trichomes indicate THC is beginning to degrade. Most growers harvest when trichomes are mostly milky with around 10 to 30 percent amber, depending on personal preference.
What nutrients do cannabis plants need during flowering?
During the flowering stage, cannabis plants generally require less nitrogen and more phosphorus and potassium than during the vegetative stage. Many growers use a dedicated bloom nutrient formula and taper off feeding in the final one to two weeks before harvest, a process sometimes called flushing. Always follow the instructions for your specific nutrient products.
How much light do cannabis plants need during flowering?
For photoperiod varieties, 12 hours of light and 12 hours of uninterrupted darkness per day triggers and maintains the flowering stage. Autoflowering plants can flower under a range of light schedules, with many growers using 18 hours of light per day throughout the full cycle. Ensure the dark period is completely dark, as light leaks can disrupt photoperiod plants and potentially cause stress.
What is the difference between flushing and not flushing before harvest?
Flushing involves watering plants with plain water and no nutrients for the final one to two weeks before harvest. Some growers believe flushing improves the taste and smoothness of the final product by clearing residual nutrients from the plant. Others dispute this and continue feeding until harvest. This is an ongoing debate among growers, and there is no definitive consensus.
What temperature and humidity should I maintain during flowering?
During the flowering stage, temperatures between 18 and 26 degrees Celsius (65 to 79 degrees Fahrenheit) are generally recommended. Relative humidity should be gradually reduced from around 40 to 50 percent in early flowering to 30 to 40 percent in late flowering to help reduce the risk of mould and encourage resin development. Avoid dramatic temperature swings between the light and dark periods.
What is bud washing and should I do it?
Bud washing involves rinsing harvested cannabis flowers in clean water before drying. Proponents suggest it removes dust, debris, and surface contaminants. Critics argue it can promote mould if flowers are not dried promptly and carefully. It is a technique used by some experienced growers but is not standard practice and is not necessary for most indoor grows.
How long does drying and curing take?
Drying typically takes 7 to 14 days, depending on temperature, humidity, and airflow. Curing in sealed jars then takes a minimum of 2 to 4 weeks, with many growers curing for 6 to 8 weeks or longer for improved flavour and smoothness. Open the jars once or twice a day for the first two weeks to release moisture.
