The cannabis flowering stage is the most rewarding part of the cultivation process for most growers. This is because it is the time when the plant delivers its sensual treats – impressive looking plants with eye candy buds and wonderful terpene aromas.
This article takes a detailed look at the cannabis flowering stage (also known as the budding stage) and gives guidelines and tips which will help the grower to boost flower production and benefit from a healthy harvest of cannabis buds.
It is during this growing phase of the cannabis plant where all the magic is happening before the grower’s eyes. Nevertheless, a successful budding period is built on the foundations of a successful vegetative stage, where the preparatory work is done to optimize plant health and flowering period potential.
For most photoperiod
Autoflowers flowering information
Autoflowers will go through the flowering process regardless of light changes (they don’t need 12/12 hours of light darkness). For Autoflowering cannabis plants the whole process – from germination to harvest – takes approximately 8 – 9 weeks.
As this article focuses on photoperiod feminized cannabis plants, please see this article which gives more information about the specific characteristics of autoflowers. An
additional guide gives useful tips for making the most of the autoflower budding stage.
What are the key characteristics of the cannabis flowering stage?
Buds are the flowers of a female cannabis plant – its final flourish of life before it fulfils its natural life cycle and dies. If the plant is fertilized by a male during the flowering stage then the plant will produce seeds.
In the cannabis flowering stage, the concentration of the plant’s energy gradually shifts from growing vertically and building branch and leaf growth to fully focus on the development of buds at the nodes of its branches.
What is the weed plant doing during the cannabis flowering stage?
The cannabis flowering stage, which follows the vegetative phase of growth, is triggered by the change in light hours the plant receives. In nature this happens naturally with the change from summer to autumn, when the daylight cycle shortens, prompting plants grown from photoperiod cannabis plant genetics to start flowering.
For indoor growers, this change is manipulated by switching the lighting in a grow room to a 12/12 (light/dark) schedule. Once the flowering process begins, this is what the plant is doing:
- The plant is forming buds! Tiny buds emerging from the nodes (where the branches meet the main stem) grow into large buds over the course of the flowering process, developing bulk, resin content and producing cannabinoids and terpenes.
- Buds are forming calyxes. These are the protective outer parts that surround the developing flowers/buds. As they grow the calyx swells and forms the basis of the bud structure.
- Buds are forming pistils. These protrude out of the calyxes and look like hairs. White to begin with, as the bud matures they will often change color, giving an indication that a weed plant is ready to harvest.
- Buds are forming trichomes. Giving buds that frosty shine, trichomes are the resinous glands which multiply as the buds develop. Microscopic in size, they also change color as the cannabis flowering stage approaches the harvest phase – from clear to white to amber.
- Buds are developing terpenes and cannabinoids. Cannabis flowers produce terpenes which create the distinctive aroma of a cannabis plant. This aroma will be different depending on the type of strain grown i.e. notes of skunk, pine, lemon etc). The plant is also developing cannabinoids (of which there are 100+).
- Leaves change color. With the plant’s energy focused on the flowers, leaves often change color (particularly with specific cannabis strains such as Sweetopia and Gulupa). With nutrients directed away from them lower leaves often become yellow and drop off.
Cannabis flowering stage timeline
Week 1- 3 in flowering: Transition
During this phase the plant is transitioning from the vegging stage to the flowering stage and will start bud formation. This will be evident in signs of pistils sprouting up at bud sites, but the actual buds will take a little time to develop.
What will be evident during this period is ‘the stretch’. When the light changes, cannabis plants will go into a period of rapid growth and for this reason, depending on the strain, the plant potentially doubles in height.
Tip: Make sure the stretch is factored into an indoor grow room setup to avoid problems with space and tops of plants being too close to the lights. For this reason consider using training techniques such as LST to manage this phase.
Week 4 – 7: Bud development
Between week 3 and 4, pistils start forming into small buds which appear like little sea anemones as they develop. They will continue to firm up and grow larger in this phase, although without packing on any real bulk.
The first dusting of trichomes can be seen. Buds may start giving off an aroma as the terpene content develops. It is at this point that nutrient feeds will be preparing the plant for bulking up in the next stage.
Tip: It’s important to be patient and work with nature. A rookie mistake is to overreact, think buds aren’t growing very fast and feed the plant more nutrients. It’s important to stick to the feeding schedule prescribed by fertilizer manufacturers to avoid issues like nutrient burn (more information about nutrient issues below).
Week 7 – 10: Ripening process
From about week 6 or 7, buds will start bulking up significantly. Pistils will start to change color on around week 7 – 8, a percentage of them turning from white to shades of orange and red.
Some leaves will discolor and drop off as the plant squeezes its lifeforce into maturing those flowers.
Trichome production will intensify, initially appearing clear and translucent, but becoming more milky as they mature. MIlky trichomes along with more than 50% of colored pistils are indications that the plant is ready to harvest.
At around week 8 or 9, it is good practice to flush cannabis plants of nutrients using just water as a feed.
Tip: During the flowering stage, plants are more sensitive to nutrients and environmental factors, such as heat and light stress. Stressed plants may produce ‘foxtails’, which are like mutant tapered buds (or spires), growing individually or sometimes even out of the side of existing buds.
What factors influence the cannabis flowering stage?
Get the light right in the cannabis flowering stage
Once the switch has been made to 12/12, the plant will do its thing and start to bud. However, there are tweaks which can be made in order to encourage bud development.
To really get into the detail of lighting check out the importance of harnessing the power of PAR, photons and UV. To get the most out of lighting in a grow room setup, consult this excellent guide on how to optimize the performance of grow room LEDS.
Another way to increase harvest potential is to use LED lights with a variable light spectrum. A deep red helps with the production of photons in the cannabis flowering stage. As the finish approaches, turning the red down and boosting blue and UVB light boosts trichome production.
Beware of ‘light leaks’ which can disrupt the lighting schedule and cause stress for plants. Ensure there are no light gaps in a grow room or grow tent and if there are, use light proof drapes and seals.
Get the temperature right in the flowering stage!
In order to keep plants happy and boost productivity of cannabinoids and terpenes, the grow room temperature should be between 20 – 26°C (68 – 79°F) during daylight hours i.e. lights on, and 15 – 20°C (59 – 68°F) in night time hours i.e. lights off.
Heat stress can result in restricted growth and stunted plants.
Get the humidity right in the flowering stage!
Humidity levels should not exceed 50% during the flowering stage (the ideal range is between 40 – 50%). In tandem with managing humidity levels, good airflow is essential.
This includes positioning fans for optimal circulation, but also paying attention to spacing between plants as overcrowding can cause an issue.
Excess humidity is one of the major contributors to issues with mold and mildew (see below).
Get the watering right in the flowering stage!
While the vegetative stage is a very thirsty time for a weed plant, once the cannabis flowering phase is reached itt will require less water.
Nevertheless, it is still important to make sure the supply is sufficient to feed internal processes such as bud development and resin production.
Insufficient water will stress a plant and cause stunted growth. Too much water may promote issues with water logged soil causing root damage and wilting leaves.
Get the nutrients right in the flowering stage!
In the flowering stage, cannabis plants require higher levels of phosphorus and potassium, which contribute to bud development and health. There are numerous fertilizers on the market (always go organic!) with precise instructions around feeding schedules.
Be careful not to over-nutrient your plants. Adding more fertilizer does not mean more and bigger buds!
On the contrary over feeding can produce nutrient issues such as nutrient burn, nutrient lock out and impact on general bud development.
Troubleshooting common issues in cannabis flowering
Canabis pest control
There are a whole host of pests which can descend on a cannabis grow and wreak havoc. Prevention is always easier than a cure (although there are plenty of pest solutions available).
A good Integrated Pest Management system is advisable, combining beneficial organisms to promote healthy plants, good hygiene and natural predators to police an emerging pest problem.
Don’t wait for signs of pest damage – by the time you see damage from a pest like spider mites the chances are they are well established. Carry out continual and through checks on plants throughout the flowering process.
Environmental stress is the major factor in turning a plant hermaphrodite (or ‘hermie’) and this can be through temperature extremes, most commonly in the form of heat stress.
A feminized plant which has turned hermaphrodite will probably pollinate the plants around it so they develop seeds within their buds.
As well as being educated in how to spot a hermaphrodite, also be aware that some modern strains are genetically more susceptible to this condition.
Some Californian cannabis varieties fall into his category so it is advised to prune using the lollipop method to prune away lower branches. This is best done in the pre-flowering or early in the flowering phase to minimize plant stress.
Mold, mildew and bud rot
Mold and bud rot is one of the biggest issues with the cannabis flowering stage, certainly for outdoor growers, but it can also be an issue in the grow room.
Indoor growing: Ensure the humidity levels don’t rise beyond 50%, and keep the air circulating. To aid with air movement, it may be necessary to trim the canopy if foliage growth is very dense to thin it out. This is best done before flowering (to minimise stress).
Outdoor growing: The unpredictability of the outdoor growing environment makes mold a real issue for many outside growers. The first consideration should be to plant genetics which have good mold resistance qualities. This guide gives excellent mold prevention tips for outdoor growing.
Should flowering cannabis plants be pruned?
While damaged or dying leaves should be removed, pruning needs careful management during the flowering stage to avoid stress and stunting plant growth.
The practice of removing healthy leaves (such as fan leaves) to open up bud sites is popular, but don’t forget that leaves still play a role in this growth stage, so defoliate with care.
The danger with pruning a cannabis plant is that once you start, juts like a bad haircut, it can get out control and too much gets taken off! Here’s a good video tutorial from the Paradise Skunkworks Project:
Ready to harvest those cannabis plants!
Having completed the cannabis flowering phase of the grow, it’s time to harvest. While this is the most enjoyable aspect of a cultivation – the fruits of your labors – it takes time and patience and it comes with its own specific considerations and potential problems!
To research this next step in great detail, refer to this comprehensive reference guide: All You Need to Know About Harvesting and Curing Cannabis.
The cannabis flowering stage of the plant’s growth needs careful management in order to ensure a productive and weighty harvest.
There are a number of problems which can affect flowering cannabis plants, such as environmental stress, management issues, pest attacks and mold/mildew infection.
The plant is more sensitive to environmental and management changes (such as nutrient feeding)in the flowering stage, so the grower must proceed with patience and diligence.
However, the benefits are plentiful, and one of the greatest rewards of all is seeing the impressive flower show provided by this amazing plant with a visual and aromatic feast for the senses!