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When does flowering start outdoors: The cannabis edition

Tom Starley
June 5, 2024
13 min read
Man inspecting cannabis plants grown outdoors on a farm
Man inspecting cannabis plants grown outdoors on a farm
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Flowering is the pivotal stage that transforms your cannabis grow from mere greenery into your well-deserved harvest. 

Understanding when flowering starts outdoors can dramatically influence the quality and potency of your yield. This post delves into exactly what you need to know. 

Your location is the key as it determines your growing season and, therefore, when flowering starts for outdoor plants.

If you don’t work with nature at the right time, fighting against it will lead to suboptimal growth, reduced potency, and even crop loss. 

We'll help you understand the flowering stage, the effects of light cycles, environmental factors, and strain differences. 

Equipped with this knowledge, you'll be prepared to optimise your outdoor cannabis cultivation for peak performance. 

Disclaimer: Any information given on this site is for educational purposes only. Please ensure if you’re growing cannabis, you’re doing so by the law and subject to appropriate permissions and licenses of the applicable country.

Grow the best cannabis and learn when and how to flower outdoors

Understanding the flowering stage

The flowering stage is a critical phase in the life cycle of your outdoor plants, marking the period when the actual buds begin to form and develop. 

This stage is not just about growth; it's when your plant's aromatic compounds and cannabinoids, like THC and CBD, are produced. Successfully navigating this phase is crucial for ensuring a high-quality harvest.

Cannabis plants can be broadly categorised into two types based on their flowering triggers: autoflowering and photoperiod strains. 

Autoflowering strains do not require changes in light cycles to initiate the early flowering stage.

These strains automatically begin the flowering process based on age, making them a preferred choice for those who seek simplicity and speed in their cannabis cultivation. 

Autoflowers are especially suitable for outdoor environments as they are generally more resilient to varying light conditions, and you can produce multiple harvests in a season.

On the other hand, photoperiod cannabis strains depend on specific light cycles to transition into the early flowering stage. 

These plants require longer periods of uninterrupted darkness to start flowering, typically needing about 12 hours of darkness each day. 

This sensitivity to light means that photoperiod strains start early flowering as the days begin to shorten post-summer solstice in the northern hemisphere or as they lengthen post-winter solstice in the southern hemisphere. 

For you, managing a photoperiod strain outdoors means paying close attention to natural light cycles or supplementing with artificial light to precisely control when flowering begins.

By understanding the distinctions between these two types of cannabis and their specific flowering triggers, you can better plan and optimise your outdoor grow, ensuring that your plants flower correctly and at the desired time. 

Close up of cannabis plants flowering outdoors

Factors that influence outdoor cannabis plants flowering 

When you're cultivating cannabis outdoors, several factors can influence the timing and success of your plants entering the flowering stage. Understanding these can help you significantly improve the quality and quantity of your yield.

Light cycles

Light cycle changes are the primary trigger for flowering in photoperiod outdoor plants. As the days start to shorten after the summer solstice in the northern hemisphere or lengthen after the winter solstice in the southern hemisphere, your outdoor plants receive the environmental cue to begin flowering. 

This change in day length triggers hormonal changes in the plants, signalling them to start developing buds. 

If you are growing photoperiod strains outdoors, it's essential to monitor daylight hours closely, as any deviation in expected light exposure can delay or disrupt this crucial phase.

Environmental factors

Besides light, several environmental factors can influence the flowering of your cannabis plants. Temperature, relative humidity, and soil conditions play significant roles. 

Cooler temperatures and higher humidity levels can delay flowering and affect the development of bud sites, potentially leading to mould or mildew issues. 

At the other end of the spectrum, optimal warm conditions can accelerate early cannabis flowering outdoors and promote healthier bud development. 

Adjusting your watering schedule and ensuring good soil drainage can mitigate some of these risks and prompt a more successful flowering phase.

Geographic location

Your geographic location also significantly impacts when and how your outdoor plants flower. 

Factors such as latitude, altitude, and local climate conditions determine the amount of sunlight your plants receive and influence local weather patterns, affecting growth. 

For instance, growers in the northern latitudes will see a later start to the bloom phase due to longer summer days. At the same time, those closer to the equator may experience more consistent light patterns, allowing for multiple growing cycles in a year.

By being aware of these factors and how they interact with your specific outdoor environment, you can better anticipate when your cannabis plants will enter the flowering stage. 

Adjustments in your cultivation approach, such as choosing the right strains for your region or modifying the micro-environment to suit your plants better, can lead to a more predictable and successful flowering period. 

Two people assessing when to flower their cannabis crop outdoors

Growing cannabis outdoors: variations among cannabis 

The timing and duration of the flowering stage can vary a lot among different cannabis strains. 

Understanding these variations is crucial for optimising your outdoor cannabis grow and achieving the best possible harvest.

Strain genetics

Cannabis strains are broadly categorised into Indicas, Sativas, Hybrids and Ruderali, each with distinct characteristics that influence their growth and flowering patterns:


Indica strains typically have a shorter flowering period, usually 6 to 8 weeks. These plants tend to be bushier and more compact, making them ideal for cooler climates with shorter outdoor growing seasons.


Sativa strains often require a more extended flowering period, which can last from 10 to 12 weeks or even longer. Sativas generally grow taller and leaner and thrive in warm climates with long, sunny days. 

Their extended flowering period requires careful planning, especially in regions where early fall weather can affect the late stages of flowering.


Hybrid strains are bred from both Indica and Sativa varieties, and their flowering times can fall anywhere between those of their parent strains. 

The specific genetics of the hybrid will determine its growth characteristics and optimal flowering conditions.


Ruderalis is another major category of cannabis that differs significantly from Indicas, Sativas, and their hybrid counterparts. 

Originating from Central Asia and Eastern Europe, Cannabis ruderalis is distinguished by its unique autoflowering trait, a survival adaptation to the short growing seasons and harsh environments of its native regions.

Unlike Indica and Sativa strains, which require specific light cycles to initiate flowering, ruderalis plants automatically begin flowering based on their age. 

This characteristic is highly valued, especially in breeding programs aimed at creating strains that can flower without the need to manipulate light cycles.

Grow the best cannabis and learn when and how to flower outdoors

Genetic adaptations to environmental conditions

The genetic background of a cannabis strain dictates the duration of its flowering stage and also how well it adapts to specific environmental conditions. 

Strains that are native to or bred for certain climates may start flowering at different times or under different light conditions than those from other areas. 

For example, strains developed for northern climates often are triggered to flower at the first sign of shorter days at the end of summer. In contrast, equatorial strains might flower under more consistent light conditions throughout the year.

Managing different strains outdoors

When growing different strains outdoors, matching each strain’s flowering requirements with your local environmental conditions is important. 

This can mean selecting strains that are known to perform well in your specific climate or particular region or adjusting your growing practices to accommodate the particular needs of more sensitive strains. 

This could include implementing shading solutions to reduce light hours or using light deprivation techniques to trigger flowering at the optimal time.

Understanding these strain variations allows you to tailor your growing strategies, ensuring each plant has the best conditions to flourish during the flowering stage. 

Cannabis flowering outdoors with mountains in the background

Preparing for the flowering stage

Proper preparation for the flowering stage is crucial to maximising the yield and quality of your outdoor cannabis grow. Here are some strategies to ensure your plants are optimally prepared to enter and succeed during this critical phase.

Nutritional needs

As your cannabis plants transition from vegetative growth to the flowering stage, their nutritional requirements change significantly. 

During flowering, plants require higher phosphorus and potassium levels to support bud formation and development. 

It's important to reduce nitrogen intake at this stage to encourage proper bud growth. Adjusting your fertiliser regimen to meet these changing needs is crucial. 

Using a bloom-specific fertiliser can help provide the right balance of nutrients that promotes robust bud production while maintaining overall plant health.

Light cycle management

For photoperiod strains, managing the light cycle is essential to initiate flowering. This involves ensuring that your plants receive uninterrupted darkness for approximately 12 hours each day. 

In an outdoor setting, natural light cycles generally provide this as the seasons change. 

However, if you're growing in a region where daylight hours do not align well with your plant's needs, using blackout tarps or sheets to create the required dark periods artificially can trigger your plants to flower at the desired time.

Ensuring optimal plant health

The overall health of your plants going into the bloom phase greatly affects the outcome. This includes regular monitoring and managing for pests and diseases, which can escalate during flowering and significantly impact bud quality and plant vitality. 

Also, proper pruning and training techniques, such as topping and low-stress training (LST), can improve light exposure to lower branches and promote even canopy development, leading to better airflow and light penetration throughout the plant.

Early signs of flowering

In the pre-flowering stage, cannabis plants start to show their sex through small pre-flowers at the nodes. This early sign is crucial for outdoor growers to identify and separate male plants from females to prevent pollination.

Recognising the early flowering signs can also help you adjust your care regimen promptly. 

These signs include the appearance of small, white pistils on a female plant, which indicate the beginning of bud formation. 

At this point, it’s crucial to minimise environmental stresses, as stress can lead to hermaphroditism or poor bud development.

You set the foundation for a successful harvest by carefully preparing for the flowering stage. 

Adjusting your care tactics to the specific needs of early flowering helps your plants thrive. It maximises the efficiency of your growing efforts, ensuring that each plant reaches its full potential. 

Woman working outside on a cannabis farm starting flowering outdoors

Optimising flowering outdoors

Optimising early flowering and the flowering stage for your outdoor cannabis plants involves more than just waiting for nature to take its course. Proactive management and environmental adjustments can significantly enhance your harvest's quality and quantity.

Bud development and support

During the flowering phase, the focus of your cultivation efforts should shift towards maximising bud health and development. Ensuring your plants have adequate support can prevent branches from breaking under the weight of bigger buds. 

Using stakes or trellises can help provide the necessary support. Additionally, consider selectively defoliating to remove leaves that shade buds, which can improve light penetration and air circulation around the burgeoning flowers.

Managing growing conditions

The micro-environment around your cannabis plants can greatly influence their flowering efficiency. Factors such as Intense sunlight, soil pH, moisture levels, and nutrient availability play critical roles. 

Ensure your plants are in a growing medium that drains well yet retains enough moisture to support this critical phase. Regular soil tests can help you maintain optimal conditions by indicating when adjustments are needed, whether it's altering pH levels or supplementing with specific nutrients.

Temperature and humidity control are also pivotal during the flowering stage. Ideal temperatures should be between 20°C to 28°C during the day and slightly cooler at night. 

Humidity levels should be lowered to around 40-50% to reduce the risk of mould and mildew, which are more prevalent during this phase due to the dense foliage and bud structure.

Also, providing enough space between plants helps maximise light exposure and air circulation, making a huge difference in overall plant health and bud quality.

If you’re keen to uncover more advanced growing tips and techniques, sign up to the Grow The Best newsletter now!

Light management

Maintaining a strict light schedule is crucial for photoperiod plants. Any light leaks during the dark period can disrupt the flowering cycle, causing stress or even reverting the plants back to the vegetative stage. 

Ensuring complete darkness is, therefore, essential. Consider using blackout covers to artificially manage the light exposure for regions where natural light periods are not ideal.

For areas with less natural light, supplementing with artificial light can help maintain the necessary light hours to support healthy growth until the natural light conditions are sufficient.

Monitoring for pests and diseases

Growing outdoors means that flowering plants are particularly attractive to pests and susceptible to diseases, which can devastate crops if not controlled. 

Regular inspections are necessary to catch and address any infestations or infections early. Implement organic pest control measures such as introducing beneficial insects or applying neem oil to avoid contaminating buds with chemicals.

By optimising these aspects during the flowering stage, outdoor growers can significantly enhance the outcome of their cultivation efforts. 

Tailored care and environmental management support healthy plant development and ensure that your cannabis plants produce potent, abundant, and beautiful buds. 

This level of attention during the flowering phase separates a mediocre harvest from a spectacular one.

Cannabis plants gfrown outside in a greenhouse

Harvesting insights

Knowing when and how to harvest your cannabis plants is as crucial as managing the flowering stage. Proper timing can dramatically impact the potency and flavour of your buds. Here’s how to determine the best time for your cannabis harvest and make the most out of your flowering efforts.

Determining the right time to harvest

The timing of the harvest is largely dependent on the maturity of the trichomes - the resin glands of the cannabis plant, which contain THC and other cannabinoids. 

These can be observed with a magnifying glass or a jeweller's loupe. Clear trichomes are not ready, while cloudy trichomes or amber trichomes indicate peak potency and maturity. 

For most strains, this visual change is a reliable indicator that the plants are ready to be harvested.

Monitoring bud development

As your plants approach the expected harvest time, it is important to pay close attention to the buds' development. 

The buds should be dense and sticky, and the pistils should turn from white to reddish-brown, indicating maturity. 

The overall size and density of the buds can also give you clues about whether they have fully developed.

Techniques for enhancing final flower quality

In the last weeks before harvest, you can employ specific techniques to enhance the quality of your flowers. 

One such technique is flushing your plants, which involves watering with plain water to remove excess nutrients. This improves the taste and smoothness of the final product.

Additionally, reducing the hours of daylight to simulate the shorter days of late fall can help increase resin production as the plants respond to the signal of approaching winter.

Harvest methodology

The method of harvesting can also affect the quality of your final product. Careful handling during the cutting and trimming is essential to preserve the delicate trichomes. 

Deciding between wet trimming and dry trimming (where you trim the leaves before or after drying, respectively) will depend on your specific drying environment and personal preference. 

Check out our beginner's guide to drying and curing for more information on wet trimming and dry trimming.

Post-harvest handling

Finally, proper curing is vital. This involves drying the buds slowly and then storing them in a controlled environment to allow chemical processes to enhance flavour and potency. 

This stage requires patience and attention to detail to prevent mould growth and to ensure the best possible aroma and efficacy of your cannabis.

By understanding these nuances of the harvesting process, you can maximise the potential of your outdoor cannabis. 

Timing, technique, and post-harvest handling all contribute significantly to the quality of your harvest, turning a good growing season into a great one.

Cannabis plants flowering outside in Parvati Valley, North India


Experienced growers know that successful outdoor growing hinges on anticipating the plants' needs rather than reacting to them. Every season provides new lessons on maximising yield and potency through careful cultivation.

Successfully navigating the flowering stage and harvesting your outdoor cannabis is critical to the culmination of your cultivation efforts.

From grasping the unique requirements of different cannabis strains during flowering to perfecting the timing of your harvest, every step demands meticulous attention and precision management.

You now know the differences between autoflowering and photoperiod strains, how environmental factors like light cycles and climate influence flowering, and the crucial role of preparing your plants for this phase.

Fine-tuning conditions during the flowering period and implementing top-notch harvesting techniques are key to unlocking your plants' full potential.

Remember, successful cannabis cultivation is a blend of art and science. It requires both passion and precision. 

With each growing season, you'll gain insights and experience that refine your skills further, enhancing your ability to produce high-quality cannabis. 

So, embrace the challenges and rewards that come with growing cannabis outdoors, and enjoy the fruitful results of your dedication.

Happy growing!


When does cannabis start flowering outdoors?

Cannabis plants typically begin flowering outdoors due to changes in daylight hours, primarily influenced by the plant's genetics and environmental cues. 

For photoperiod cannabis strains, the transition to flowering is triggered by decreasing daylight after the summer solstice or increasing daylight after the winter solstice, depending on the hemisphere. 

This change in the light cycle initiates the flowering phase when the plants receive less daylight, usually around 12 hours per day. 

This natural adaptation helps the outdoor cannabis plants maximise reproductive success by flowering at a time conducive to pollination and seed maturation before the colder months. 

The specific timing can vary based on strain characteristics and local climate conditions, but this light-dependent trigger is a crucial factor in determining when cannabis begins to flower outdoors.

How long does it take for cannabis to show signs of flowering?

Once the flowering phase is triggered in cannabis plants, it typically takes about one to three weeks for the first signs of flowering to become visible. 

This initial phase is known as the pre-flowering stage, where you might start to see the development of small, white, hair-like structures called pistils on female cannabis plants. These pistils emerge at the plant’s nodes, which are the areas where the branches meet the stem.

The exact timing can vary based on several factors, including the strain of the cannabis, the growing conditions, and whether the plant is an autoflowering or photoperiod variety. 

Autoflowering cannabis strains generally show signs of flowering sooner (usually within two to four weeks after seed germination), regardless of the light cycle. 

In contrast, photoperiod strains require a change in the light cycle to initiate flowering and will show signs after the required dark periods are met consistently.

When to start bloom nutrients outdoors?

If you’re growing outdoor cannabis, time the switch to bloom nutrients to coincide with the onset of flowering. 

Begin when daylight hours decrease, typically when days shorten after summer. Switch to bloom nutrients as soon as you see the first signs of flowering, like white pistils at the nodes. 

Transition gradually by mixing bloom nutrients with vegetative nutrients over about a week. Continue with bloom nutrients throughout the flowering stage to support bud development and plant health.

Grow the best cannabis and learn when and how to flower outdoors
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Tom Starley
June 5, 2024
13 min read

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