Article written by
Homegrown Cannabis Co.American Seed Bank and Cultivation Experts
Content reviewed by
Dr. Lewis JasseyMedical Director - Pediatric Medicine
Table of contents
The cannabis flowering stage demands plenty of sunlight, phosphorus, potassium, and tender care. This period is immensely satisfying because it lets you see the fruits of your labor. Plants become heavy with buds and get stickier and stronger-smelling by the day.
Marijuana is very vulnerable in flowering, and slip-ups can reduce the yield quantity and quality. Stay on top of plant health in the home stretch, and you’ll soon be consuming first-rate weed.
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What Is the Flowering Stage?
The flowering stage is the fourth and final step of growing cannabis. It occurs after the vegetative stage and before the harvest. During this time, the plant produces buds to be dried, cured, and consumed later.
Vegging weed spends its energy elongating the stem and sprouting limbs and foliage. Once flowering commences, reproductive organs emerge on the internodes (where the stalk meets the leaves).
Flowering is an evolutionary process to propagate the species, so the difference in plant sex becomes apparent early in this stage. Male plants sprout round pollen sacs; females produce oblong pods with pistil hairs.
In nature, these organs appear as the fall approaches. Males pollinate females and produce new cannabis seeds, letting the population persist for another generation. If you keep fems safe from pollen, they yield seedless, smokable buds.
These blossoms start as small flower sites and eventually grow into buds. As they mature, trichome glands appear and start oozing resin. This sticky material makes weed potent and flavorful.
Flowers gather into colas: the main one on top and many smaller ones along the side branches. Sugar leaves surround and protect them. If you topped in vegging, there are now multiple main colas.
Since it’s an annual species, the marijuana plant reaches maturity before the chilly fall days, finishing its yearly life cycle.
How Long Does Flowering Last?
Cannabis flowering may last 6-12 weeks, depending on the strain (more accurately called “cultivar”) and variant.
Indica originates from harsh areas with short summers and usually ripens in two months. Sativa is from tropical regions and may take three or more months to mature. It is possible to have both sativas and indicas in some regions with various altitudes, as sativa varieties can grow in lowland areas and indicas in highland areas.
Expert tip: Does the fall come quickly in your state? Fast-version seeds from Homegrown Cannabis Co. finish flowering two weeks before their regular counterpart. They’re perfect for outdoor cannabis cultivation in colder regions.
The start depends on the seed variant:
- Photoperiod plants remain in vegging while there are 16 hours of light daily. They only flower when the daytime duration drops to 12 hours.
- Autoflower plants develop based on age, not the light cycle. They veg for 5-6 weeks and automatically bloom after, regardless of the sun or your lamps. You may keep them under an 18/6 schedule throughout.
Indoor cultivators who use photoperiod seeds trigger flowering by flipping the lights and changing the schedule from 18/6 to 12/12. Outdoors, it begins in late July or early August.
Plants stop growing and sprout pre-flowers in the first 2-3 weeks of this stage. Buds fatten and become sticky with trichomes over the following month or two.
Flowering ends when you cut down the plant and remove its buds for drying. The harvest should occur when the pistils curl inward, trichomes become opaque, and a powerful scent permeates the grow room.
Caring for Your Flowering Cannabis Plant
Blooming cannabis plants enjoy warm areas (70-80°F) with moderate humidity (35-55%) and intense sunlight or lamps (LED or HPS). They’re sensitive to climate fluctuations and light leaks, requiring meticulous care to flourish.
Let’s discuss every aspect of plant care in the cannabis flowering stage.
Flipping the Lights
The flowering phase is easy to predict. Indoor growers choose when it begins, while outdoor and greenhouse cultivators safely rely on the calendar. You can use this information to your advantage.
Budding plants are vulnerable, so ensure they’re perfectly healthy before they flower. Inspect the medium, foliage, and stem for damage and act accordingly.
Do your final transplant into a bigger pot several weeks before flowering. Also, prune the unnecessary fan leaves to boost the airflow and light penetration.
The days gradually shorten outdoors, and you should mimic this switch indoors. Instead of surprising plants with 12 hours of uninterrupted darkness, reduce the daylight duration by an hour per day. That way, you minimize the shock and help them remain healthy.
Weed requires less moisture during the flowering stage. Only shower plants when they use most of the medium’s available water.
Overwatering and underwatering damage the roots, so adjust the frequency based on what you see in your garden. You can gauge the situation by sticking a finger in the growing medium. The top 1-2 inches should feel dry between feedings.
Expert tip: If the soil takes more than 3-4 days to dry, you might have drainage issues. Introduce organic matter or poke additional holes in the container to address them.
Ensure that your water source is pH-optimized for marijuana. To enable nutrient absorption, it should be slightly acidic (5.8-6.2).
The cannabis flowering cycle introduces an increased need for phosphorus and potassium. Since the plants no longer develop as much new foliage, they use much less nitrogen.
You can accommodate this need by supplying the highest-quality flowering nutrients. These products contain optimized amounts of all necessary minerals, so follow the manufacturer’s instructions on feeding dose and frequency.
Don’t abruptly switch your nutrients. Instead, follow the provided feeding chart, which usually suggests a mix of veg and bloom fertilizers. You might also give plants extra calcium and an occasional dose of fulvic acid for better health.
Be mindful of nutrient burn and deficiency during this stage. Check and correct the pH before changing the feeding schedule if you see leaf yellowing, curling, and drying.
Many growers stop feeding in the final 1-2 weeks of flowering to let plants use the existing nutrient store.
Flowering cannabis needs 12 hours of intense light exposure and 12 hours of absolute darkness daily. Inconsistencies can revert it to veg or cause hermaphroditism (where female plants sprout pollen sacs and self-fertilize).
If cultivating in outdoor land or a greenhouse, pick a spot with at least six hours of direct sunlight. Install opaque materials around the garden if street lamps, vehicles, or billboards cast light on them at nighttime.
Indoor growers meet this need with grow lights:
- HID lamps: Inexpensive to set up and provide the entire light spectrum but emit a lot of heat. Keep them at least 12 inches above the canopy to avoid burning the cola.
- LED lamps: Initially pricier but with low operational costs and excellent coverage. Choose either full-spectrum or red light for flowering.
If you’re cultivating autoflowers, you may keep them under an 18/6 schedule throughout the blooming phase. They don’t depend on darkness, and more light means fatter buds.
Install intake and extractor fans in your grow room or tent and supplement them with wall-mounted fans if necessary. Position your outdoor garden or greenhouse in the wind direction.
Growers who want to keep their gardens discreet may install carbon filters. These devices scrub the aromatic molecules through activated carbon, containing the odor within the space.
Cannabis absorbs nutrients best in slightly acidic environments (6.0-7.0 pH in soil and 5.5-6.5 in hydroponics). Keeping a close eye on pH levels helps you avoid nutrient deficiency, burn, and toxicity.
Measure these levels every time you feed and water. If using soil, check your water source, nutrient solution, and runoff to identify imbalances at any level. Hydroponic cultivators should measure the pH of their fertilizer and reservoir.
Flush the pot or tank if there’s an imbalance. Then treat it with a pH-optimized nutrient solution to keep plants healthy and well-fed.
Temperature and Humidity
Plants need moderate heat and humidity while growing buds. They’re the healthiest when these two metrics remain in check.
The appropriate temperature range is 70-80°F during the daytime and 65-75°F at nighttime. Higher temperatures make the trichomes dry out. Experienced growers may keep their nights at 55°F in the final weeks of flowering to bring out the coloration of purple strains.
Low humidity is key to getting dense buds. Start this stage with 55% relative humidity and reduce it by 5% in each following week of the life cycle. It should be 35-40% during the last ten days before the harvest.
The Flowering Stage Week by Week
The flowering cycle happens in three stages:
- Pre-flowering stage: A final vegetative growth spurt and first signs of sex.
- Bud production stage: White hairs multiply and thicken, producing proper flowers.
- Ripening stage: Trichome glands activate, and resin covers the flower surface.
Let’s see what you can expect in each.
Weeks 1-3: Stretch and Flower Initiation
Plants stop developing when they bloom, but only after a final intense spurt of vegetative growth. We call this phenomenon the flowering stretch, as it might make your marijuana double in height and sprout many new leaves.
During the first week of flowering, plants are still strong and capable of handling stress. The growth may continue in the second week, which also introduces pre-flowers.
Pre-flowers are bits of tissue that serve as a basis for future reproductive organs. They also help you gauge plant sex:
- Males have round bags to be filled with pollen and burst.
- Females have pairs of pistils on top of teardrop-shaped calyxes.
Inspect and separate males from females as soon as you identify their sexes. You can also switch to bloom-time fertilizer in the second week.
The stretch stops in the third week, and you see the first signs of bud sites. Bunches of single leaves appear around the white pistils. Plants get fussier about the environment, so pay extra attention to climate control.
Weeks 4-5: Bud Production
At week four, small pre-flowers multiply and become dense, forming the cannabis buds. Pistils protrude on top and are still white in this early section.
The first trichome glands appear around the fifth week. The smell is still slight and mostly vegetal, though. Some pistils might start darkening, although they’re far from the rusty harvest-ready hue.
Beware of disease symptoms in the bud production stage: the canopy should look lush and green. You might see some yellowing blades at the base, but if numerous curl and die, take action to save your cannabis.
Weeks 6-8: Ripening
Most strains need at least eight weeks to reach perfect maturity. The final few weeks before the harvest make up the ripening stage, where no more branch of leaf growth occurs. Buds become larger, stickier, and stronger-smelling by the day.
The leaves start yellowing and falling off at the bottom sections, but the upper areas still look healthy. Reduce relative humidity to 40% to avoid mold and rot.
Some plants appear perfectly ripe by week eight. They have rusty brown pistils that curl inward, and most trichomes are cloudy instead of transparent. Combine the visual info with your strain’s expected flowering time to pinpoint the optimal harvest window.
Week 9 and Beyond: Harvest
As the harvest date appears, you can take the final few actions to improve the bag appeal of your weed.
The first is flushing the medium of excess nutrients a week before the harvest to improve bud flavor. Stop administering fertilizer and shower the plant with plain water. It uses up any lingering minerals and loses the chemical tinge of fertilizer from its aroma.
You might also expose your weed to lower nighttime temperatures. Cannabis might increase its trichome production when kept in spaces under 65°F. Some strains also have a purple pigment, which comes out the most when the nights are around 55°F in the last week of flowering.
Tips for an Optimal Harvest
The flowering phase concludes a long and integrated gardening journey. What you do before, during, and after this period affects the quality of your weed.
You get the heaviest and stickiest yields by making the right decisions from seed to harvest and beyond. Here are several handy tips to increase your success rates:
- Use feminized seeds. This variety produces only female cannabis plants. It minimizes the risk of pollination, making it easier to get seedless buds.
- Mind the light intensity. Strong lamps help buds fatten, but they can burn and dry the colas if kept too close. As a rule, LEDs should sit 24 inches above the canopy, and HPS lamps may safely stay 12-24 inches away from it.
- Watch the humidity. High moisture levels make the buds light, airy, and sometimes even moldy. Keep the air dry for healthy and dense flowers.
- Space out the plants. Leave half a foot between the canopies of each pot. This organization makes it easier for light to reach the side colas.
- Install branch support. Slimmer strains might buckle under the bud weight in late flowering. String the stalk to bamboo stakes or trellis net to keep them from breaking.
- Time the harvest right. Buds aren’t as fragrant as possible until at least half of the trichomes become opaque. Potency declines with age. So, examine the colas with a magnifying glass and only cut them when they’re perfectly ripe.
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